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  • 2005-2009
  • 1995-1999  (207)
  • 1965-1969
  • 1999  (207)
  • Analytical Chemistry and Spectroscopy  (132)
  • nitrogen  (75)
  • Organic Chemistry
Source
Material
Years
  • 2005-2009
  • 1995-1999  (207)
  • 1965-1969
Year
Keywords
  • 101
    Electronic Resource
    Electronic Resource
    High Speed Cryogenic Modulation - A Technology Enabling Comprehensive Multidimensional Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 235-238 
    Details
    ISSN: 0935-6304
    Keywords: Cryogenic modulation ; LMCS ; GC×GC ; multidimensional GC ; comprehensive gas chromatography ; petroleum analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 102
    Electronic Resource
    Electronic Resource
    Heptakis(6-O-ethyl-2,3-O-pentyl)-β-cyclodextrin: A New Chiral Stationary Phases for Capillary GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 242-244 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; 6-O-ethyl-2,3-O-pentyl-β-cyclodextrin ; essential oils ; carboxylic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 103
    Electronic Resource
    Electronic Resource
    Determination of Amitraz in Cattle Dipping Baths by High-Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 247-249 
    Details
    ISSN: 0935-6304
    Keywords: High performance liquid chromatography-ultraviolet detection (HPLC-UV) ; Amitraz ; cattle dipping bath ; pesticide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 104
    Electronic Resource
    Electronic Resource
    On-Line Coupled Liquid Chromatography - Gas Chromatography in the Analysis of Process Samples (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 261-264 
    Details
    ISSN: 0935-6304
    Keywords: On-line coupled LC-GC ; normal phase liquid chromatography ; process samples ; oxygenated compounds ; partially concurrent solvent evaporation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Normal phase liquid chromatography-gas chromatography was used with on-column interfacing and partially concurrent solvent evaporation in the analysis of process samples. Samples were taken from reaction mixtures, where the solvent was toluene. The analytes were oxygenated compounds: methyl isobutyrate, methyl methacrylate, methyl α-formyl isobutyrate, and methyl β-formyl isobutyrate. The analytes were transferred from LC to GC using back-flush with a solvent mixture of pentane and diethyl ether. Linearity, repeatability, and transfer efficiency were determined for the method. The method was applied in the determination of the analytes of two different process samples. The results were in good agreement with results obtained by the gas chromatographic method currently in use for the analysis of the process samples.
    Additional Material: 2 Ill.
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  • 105
    Electronic Resource
    Electronic Resource
    Determination of the Critical Micelle Concentration of Cationic Surfactants by Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 265-270 
    Details
    ISSN: 0935-6304
    Keywords: Critical micelle concentration ; cationic surfactant ; capillary electrophoresis ; tetradecyltrimethylammonium bromide ; dodecyltrimethylammonium bromide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The determination of the critical micelle concentration (CMC) of cationic surfactants by capillary electrophoresis was demonstrated. In this study, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DoTAB) were selected as cationic surfactants and propazine was chosen as test solute. In the evolution of the effective electrophoretic mobility of propazine as a function of surfactant concentration, a dramatic change in slope at a particular concentration is a good indication of the CMC of this surfactant. The CMC values determined experimentally were further confirmed by a curve-fitting approach. Simulation of the electrophoretic mobility curves as a function of surfactant concentration in both micellar electrokinetic chromatography and capillary zone electrophoresis using cationic surfactants as an electrolyte modifier was performed for propazine, and the intersection of these two mobility curves allowed us to precisely predict the CMC of the surfactant. The CMC values determined for TTAB and DoTAB are 1.6 ± 0.1 and 11.0 ± 0.1 mM, respectively, in the case of an electrolytic solution consisting of 70 mM phosphate buffer at pH 6.0. Moreover, the applicability of the electroosmotic mobility as a parameter for the determination of the CMC was examined.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 106
    Electronic Resource
    Electronic Resource
    A Unified Sample Preparation System for Extraction of Various Analyte/Matrix Combinations (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 271-275 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; enhanced solvent extraction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A supercritical fluid extraction/enhanced solvent extraction system (SFE/ESE) was used to remove polar and non-polar analytes from various matrices. Extraction of environmental pollutants from soil, additives from low density polyethylene, sulfa drugs from animal tissue, and drug from tablet was performed using both SFE and ESE. Results showed that a single instrumental system can be used to perform both ESE with organic solvents and SFE with carbon dioxide-based fluids. Each method has its own unique advantages and applications. The ability to carry out both solvent extraction and supercritical fluid extraction with one system has obvious economical advantages.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 107
    Electronic Resource
    Electronic Resource
    An Improved Interface for Coupling Solid-Phase Microextraction (SPME) to High Performance Liquid Chromatography (HPLC) Applied to the Analysis of Explosives (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 279-282 
    Details
    ISSN: 0935-6304
    Keywords: Solid phase microextraction (SPME) ; SPME/HPLC interface ; C-8 refocusing unit ; explosives analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 108
    Electronic Resource
    Electronic Resource
    Analysis of the Naturally Occurring Pesticide Rotenone by Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 294-296 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; capillary ; fused silica ; rotenone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 109
    Electronic Resource
    Electronic Resource
    Isolation of Polychlorodibenzo-p-dioxins and Polychlorobiphenyls upon Deproteinization of a Serum Sample by HPLC with Restricted-Access Reversed-Phase Packing Materials (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 287-293 
    Details
    ISSN: 0935-6304
    Keywords: Deproteinization ; polychlorobiphenyls ; polychlorodibenzo-p-dioxins ; restricted-access reversed-phase packings ; sample preparation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 110
    Electronic Resource
    Electronic Resource
    Determination of Trichothecene Toxin (T2 Mycotoxin) in Aqueous Sample with Solid Phase Microextraction Technique Followed by Gas Chromatography with Flame Ionization Detection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 424-426 
    Details
    ISSN: 0935-6304
    Keywords: Mycotoxin ; T2 ; solid phase microextraction ; GC/FID ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 111
    Electronic Resource
    Electronic Resource
    Preparation of On-Column Frits in Packed Fused Silica Capillaries by Sol-Gel Technology (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 438-442 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; micro-HPLC ; preparation of on-column frits ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Existing methods for preparing frits in packed fused silica capillaries as used for electrochromatography and micro HPLC are not applicable to all silica based packing materials and involve a high thermal stress for both the stationary phase and the fused silica tubing including the polyimide coating. A new procedure for the production of such on-column frits under mild conditions by a sol-gel type reaction of polydimethoxysiloxane (PDMOS) is described in this paper. Reaction conditions were established for optimum mechanical stability and high permeability of the frits. Frits produced in this manner showed no noticeable effect on the overall efficiency.
    Additional Material: 1 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    Application of Temperature and Applied Voltage Programming in Micellar Electrokinetic Capillary Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 443-448 
    Details
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic capillary chromatography ; temperature programming ; applied voltage programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Temperature and voltage programming modes were utilized to optimize selectivity and increase the eluting rate of strongly retained compounds in micellar electrokinetic chromatography. Separations obtained by applying temperature, voltage, and a simultaneous combination of temperature and voltage gradient in micellar electrokinetic capillary chromatography were compared with separations performed under isothermal and constant voltage conditions. A complete separation of all the constituents of the test mixture was only achieved in the temperature programming run and in a combination of temperature and voltage programming modes. Simultaneous variations of column temperature and applied voltage during a separation run, yielded a 30% reduction in the total analysis time when compared to a temperature gradient alone. Temperature programming and voltage programming modes may be the gradient methods of choice because of the considerable technical difficulties involved in performing linear solvent gradient elution in micellar electrokinetic chromatography.
    Additional Material: 7 Ill.
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  • 113
    Electronic Resource
    Electronic Resource
    Fast Temperature Programming in Gas Chromatography using Resistive Heating (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 459-464 
    Details
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; gas chromatography ; resistive heating ; organophosphorus pesticides ; PAHs ; triazines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed inside a metal tube which can be heated, and cooled, much more rapidly than any conventional GC oven. The EZ Flash assembly can generate temperature ramps up to 1200°/min and can be cooled down from 300 to 50°C in 30 s. Samples were injected via a conventional split/splitless injector and transferred to the GC column. The combination of a short column (5 m×0.25 mm i. d.), a high gas flow rate (up to 10 mL/min), and fast temperature programmes typically decreased analysis times from 30 min to about 2.5 min. Both the split and splitless injection mode could be used. With n-alkanes as test analytes, the standard deviations of the retention times with respect to the peak width were less than 15% (n = 7). First results on RSDs of peak areas of less than 3% for all but one n-alkane indicate that the technique can also be used for quantification. The combined use of a short GC column and fast temperature gradients does cause some loss of separation efficiency, but the approach is ideally suited for fast screening as illustrated for polycyclic aromatic hydrocarbons, organophosphorus pesticides, and triazine herbicides as test compounds. Total analysis times - which included injection, separation, and equilibration to initial conditions - were typically less than 3 min.
    Additional Material: 7 Ill.
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  • 114
    Electronic Resource
    Electronic Resource
    Determination of Deuterated Phenylalanine and Tyrosine in Egg Protein by GCQ (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 465-468 
    Details
    ISSN: 0935-6304
    Keywords: Amino acid ; stable isotope ; GC-MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In order to study protein digestibility by means of noninvasive tracer techniques (stable isotopes), a representative oral tracer, i.e. a stable isotope labeled protein, is needed. Therefore, egg white containing L-[ring-2H5]phenylalanine and L-[ring-2H4]tyrosine was prepared. The aim of this study was to measure the isotopic enrichment of the labeled amino acids in the egg white. The use of a standard GC-MS, based on ion trap technology was found to be a reliable technique. The enrichment of L-[ring-2H5]phenylalanine and L-[ring-2H4]tyrosine, expressed in Molar Percent (MP) amounted to 23.2 MP and 2.8 MP respectively.
    Additional Material: 4 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    Development of a Methodology for the Identification of Volatiles in Industrial Adhesive Formulations by GC/MS with Manual Headspace Sampling (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 477-480 
    Details
    ISSN: 0935-6304
    Keywords: Adhesives ; GC/MS ; headspace analysis ; poly(vinyl acetate) ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 116
    Electronic Resource
    Electronic Resource
    High Resolution Separation of Non-Polar Lipid Classes by HPLC-ELSD Using Alumina as Stationary Phase (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 483-486 
    Details
    ISSN: 0935-6304
    Keywords: HPLC ; alumina ; evaporative light-scattering detection ; non-polar lipids ; wax esters ; sterol esters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study describes the performance and capacity of alumina as stationary phase in an HPLC-ELSD (evaporative light-scattering detection) method optimized for the separation of the non-polar lipid classes hydrocarbons, wax esters, sterol esters, triacylglycerols, and sterols, including quantitative determination of these lipid classes in natural samples. By using gradient elution and constant equilibration times between injections, highly reproducible separations of triacontane, stearyl oleate, and cholesterol oleate were accomplished with a binary mobile phase system. Phase A contained 0.5% tetrahydrofuran in hexane and phase B 20% isopropanol and 20% tetrahydrofuran in hexane. The same system was also used to determine the non-polar lipid classes in a zooplankton sample, the major lipid class being wax esters, followed by triacylglycerols, sterol esters, sterols, and hydrocarbons. Substantial amounts of an unknown compound, possibly acylated glyceryl ethers, were also found. The equilibration time of alumina was relatively slow compared to a polyvinyl alcohol stationary phase used earlier by the authors and calibration curves for different lipid classes were more uniform and linear with alumina.
    Additional Material: 4 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    Prediction of Migration Times of Organic Ions in Capillary Zone Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 495-500 
    Details
    ISSN: 0935-6304
    Keywords: CZE ; mobility ratio ; migration time prediction ; mathematical model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The electrophoretic mobility ratio (R value) of any two ions is constant and independent of the capillary type and electrophoretic conditions if their electrical charges and hydration radii are constant. The use of strong acid salts and quaternary ammonium salts is therefore proposed for the determination of R values. Such analytes are called markers. The following determinations can be carried out: (i) the determination of the migration time corresponding to the electroosmotic flow (EOF) in any capillary under any electrophoretic condition by measuring the migration times of two markers in the condition studied (useful when the EOF is weak); (ii) the determination of the migration time of an analyte in any capillary by knowing the migration time of the markers in the capillary studied. If the pH is changed and the ionization of the analyte is pH dependent, the resulting migration time for the analyte can be calculated. The constancy of the mobility ratios of seven markers was checked experimentally at eight different pH values (between pH 3 and 10), at three temperatures, and for two buffer concentrations. The predicted and experimental migration times were also compared in two different types of capillaries.
    Additional Material: 2 Ill.
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  • 118
    Electronic Resource
    Electronic Resource
    Possibilities and Limitations of Fast Temperature Programming as a Route towards Fast GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 509-513 
    Details
    ISSN: 0935-6304
    Keywords: Fast GC ; fast temperature programming ; resistive heating techniques ; short columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---One possible way to speed up a gas chromatographic analysis is the application of fast temperature programming by using resistive heating techniques. With this heating technique programming rates up to 20° per second can be reached. A relative standard deviation of retention times better than 0.2% is obtained. Using fast temperature programming the analysis-times of a mineral oil sample, an industrial oligomer sample, and toxic compounds in diesel fuel have been reduced 5 to 20 times, compared to a standard temperature programmed analysis. In most cases resistive heating cannot be applied to reduce the analysis time of a complex sample. The use of fast temperature programming is preferable to the use of short columns and columns operated at above-optimum carrier gas velocities.
    Additional Material: 6 Ill.
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  • 119
    Electronic Resource
    Electronic Resource
    Trace Determination of Organic Compounds in Water by Direct Enrichment in Multichannel Thick Film Silicone Rubber Traps with Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 521-526 
    Details
    ISSN: 0935-6304
    Keywords: Multichannel silicone trap ; water analysis ; flow rate ; methanol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of Multichannel Silicone Rubber Traps for the direct analysis of organic compounds in water was studied. The optimum collection flow rate for a 10 mL sample was found to be ca. 150 μL·min-1. The effect of methanol on the retention power of the trap was evaluated. The addition of a methanol fraction of up to 40% to the water standards did not show any loss in collection efficiency. It was shown that the extraction of organic compounds from water with the multichannel trap is uncomplicated, i. e. methanol is not required to achieve accurate analyses, concentration of the sample onto the trap is by gravity flow, and excess water remaining in the multichannel trap after water extraction is removed by centrifugation. With the use of the multichannel silicone rubber trap a wide boiling point range of compounds were analyzed from aqueous samples at levels of 1-4 μg·L-1.
    Additional Material: 5 Ill.
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  • 120
    Electronic Resource
    Electronic Resource
    Improved Procedure for Single DB-XLB Column GC-MS-SIM Quantitation of PCB Congener Distributions and Characterization of Two Different Preparations Sold as “Aroclor 1254” (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 533-540 
    Details
    ISSN: 0935-6304
    Keywords: Chlorobiphenyl congeners ; Aroclor 1254 ; DB-XLB phase ; GC-MS-SIM ; PCB 126 ; toxic equivalency ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Complete PCB congener distributions in a panel of Aroclor mixtures were previously obtained by combining data from several HRGC systems. In that study quantitation of minor components may have been unreliable due to single level calibration against high levels of individual congener standards. Two lots of Aroclor 1254 had markedly different congener distributions. In this study, the design and performance of a congener-specific PCB analysis method employing GC-MS-SIM detection of congeners separated on a DB-XLB capillary column are discussed. Quantitation is carried out against a 6-level inclusive standard curve of a mixture of 144 congeners found in Aroclors. A separate procedure to measure trace levels of PCB 126 in Aroclors using the same system, combined with levels initially acquired for other congeners, facilitates estimation of TEQ values (Toxic Equivalencies of the PCB mixtures to 2,3,7,8-TCDD). PCB congener profiles of 15 Aroclor 1254 mixtures are presented. These profiles show that the less common, high TEQ variety of Aroclor 1254 was manufactured by an atypical, two-stage chlorination process that was apparently used during the final 1% of Aroclor 1254 production (ca. 1974-1976).
    Additional Material: 5 Tab.
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  • 121
    Electronic Resource
    Electronic Resource
    Functionalized Polymeric Sorbents for Solid-Phase Extraction of Polar Pollutants (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 547-552 
    Details
    ISSN: 0935-6304
    Keywords: Water analysis ; polar pollutants ; solid-phase extraction ; chemically-modified polymeric resins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This study assesses how the physical characteristics of styrene-divinylbenzene (PS-DVB) resins affect the extent to which they are modified when they are functionalized, and how they affect recoveries in on-line solid-phase extraction (SPE) of some polar phenolic compounds, pesticides, and metabolites from water samples which were analyzed by liquid chromatography and UV detection. For this purpose, three commercial PS-DVB resins with different physical characteristics (Amberchrom GC-161m and two different PLRP-S resins) were chemically modified by placing a hydrophilic group, an o-carboxybenzoyl moiety, on their surface; although the physical characteristics are different, the extent of modification did not vary significantly. The results from the SPE process with each sorbent were related to their physical and chemical properties. The polymers with higher surface area provided better recoveries. Moreover, the recoveries for these analytes were better with the chemically-modified polymers due to the higher polarity of these sorbents. The best recovery values were with the sorbent obtained from the chemical modification of Amberchrom GC-161m, the commercial sorbent with higher surface area. For instance, in the analysis of 50 mL of a sample of 2 μg L-1, the recovery of phenol was 40% with Amberchrom GC-161m and 65% with the chemically-modified Amberchrom GC-161m.
    Additional Material: 3 Ill.
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  • 122
    Electronic Resource
    Electronic Resource
    γ-Dithiolactones - Analytical and Sensory Characteristics (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 421-423 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective gas chromatography ; 2,3-di-O-methyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin ; 2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin ; γ-dithiolactones ; olfactometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 123
    Electronic Resource
    Electronic Resource
    Determination of Biological Oxidative Stress Using High Performance Liquid Chromatography with Electrochemical Detection (HPLC-ECD) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 429-437 
    Details
    ISSN: 0935-6304
    Keywords: HPLC ; nitrotyrosine ; nitrotocopherol ; analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---For three decades, high performance liquid chromatography has proven itself to be a powerful, flexible, and inexpensive tool for basic and clinical research. Recent advances in our understanding of disease have prompted a demand for more sensitive and selective methods of routine bioanalysis, particularly with respect to the determination of oxidative metabolites and biomarkers of oxidative stress. Multidimensional detectors utilizing coulometric arrays offer a solution to these research needs. The challenge to the bioanalyst is now to creatively apply HPLC-ECD technology to promising research and clinical enterprises.
    Additional Material: 9 Ill.
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  • 124
    Electronic Resource
    Electronic Resource
    Optimization and Parameter Study for Chiral Separation by Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 449-453 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; experimental design ; cyclodextrin ; chiral separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Orthogonal design and uniform design were used for the optimization of separation of enantiomers using 2,6-di-O-methyl-β-cyclodextrin (DM-β-CD) as a chiral selector by capillary zone electrophoresis. The concentration of DM-β-CD, buffer pH, running voltage, and capillary temperature were selected as variable parameters, their different effects on peak resolution were studied by the design methods. It was concluded that orthogonal design offers a rapid and efficient means for testing the importance of individual parameters and for determining the optimum operating conditions. However, for a large number of both factors and levels, uniform design is more efficient. The effect of addition of methanol and citric acid buffer on the separation of enantiomers was also examined.
    Additional Material: 5 Ill.
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  • 125
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    Prototypical Test Substances for a Reversed Phase in a Retention Parameter Model (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 454-458 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; reversed phase ; prototypical substances ; retention parameter model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A set of four prototypical substances (naphthalene, acetanilide, phenol, and benzonitrile) is selected from 26 different analytes used by Seibert and Poole for characterization of the retention behavior of 20 liquid chromatographic systems of a C18 reversed phase with methanol/water and acetonitrile/water as mobile phases. Retention data of 22 different analytes can be calculated from the retention data of the set of prototypical substances with a mean standard deviation of 5.4%. Two phase system maps similar to that suggested by Poole et al. are provided for an octadecylsiloxane-bonded silica sorbent with methanol and acetonitrile as cosolvents with water.
    Additional Material: 2 Ill.
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  • 126
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    Determination of Organic Peroxides by Gas Chromatography with Cold On-Column Injection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 475-476 
    Details
    ISSN: 0935-6304
    Keywords: Organic peroxides ; gas chromatography ; FID ; cold on-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 127
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    Modifier and Additive Effects in the Supercritical Fluid Extraction of Pseudoephedrine Hydrochloride from Spiked-Sand and Suphedrine Tablets (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 469-474 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; SFE modifiers ; pseudoephedrine ; suphedrine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The effect of modifier and additive composition upon pseudoephedrine recovery from spiked-sand and Suphedrine tablets was examined. Recovery was shown to be dependent on CO2 density as well as on the addition of an ion pairing agent to the matrix. The presence of methanol in the extraction vessel prior to SFE was shown to play a significant role in the ion-pair extraction process. Recovery was also shown to be a function of ion-pairing reagent composition and concentration. The most successful recovery was obtained in the presence of 1-heptanesulfonic acid (HSA), sodium salt in methanol at a 5:1 molar ratio (reagent to drug). The increased extractability in the presence of ion-pairing reagent was attributed to reduced analyte polarity and analyte-matrix displacement. Alternatively, a matrix-spiked mixture of methanol and 1% water by itself was just as effective as a matrix-spiked mixture of methanol and HSA for attaining efficient extraction. Several in-cell (e. g. to the matrix) and in-line (e. g. to the fluid) modifiers were examined for the extraction of pseudoephedrine from Suphedrine tablets. The greatest pseudoephedrine recovery from Suphedrine tablets of 82% (7.0%) was achieved with 10% (l% H2O) methanol-modified CO2 in the presence of 400 μL of methanol (l% H2O). Finally AgCl tests and infrared analyses were performed on two tablet extracts. It was confirmed that even in the absence of any in-cell modifier, a small fraction of pseudoephedrine hydrochloride could be extracted.
    Additional Material: 5 Ill.
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  • 128
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    Chiral Separation of Carboxymethyl Derivatives of Amines by Liquid Chromatography on Reversed-phase Silica Gel Coated with N-n-Dodecyl-L-hydroxyproline (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 487-489 
    Details
    ISSN: 0935-6304
    Keywords: Carboxymethyl derivatives of amines ; dodecyl-L-hydroxyproline ; chelate ring ; chemiluminescence ; ruthenium complex ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Carboxymethyl derivatives of amines containing a chiral α-carbon were separated into enantiomers by high-performance liquid chromatography using octadecylsilanized silica gel coated with N-n-dodecyl-L-hydroxyproline as the stationary phase and an aqueous solution containing copper(II) as the mobile phase. Detection was by post-column reaction involving derivatization to tertiary amine and chemiluminescence reaction of ruthenium bipyridine complex.
    Additional Material: 3 Ill.
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  • 129
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    Temperature-Programmed Packed Capillary Liquid Chromatography Separation with Large Volume On-Column Focusing of Retinyl Esters (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 490-494 
    Details
    ISSN: 0935-6304
    Keywords: Large volume injection ; packed capillary LC ; temperature programming ; retinyl esters ; vitamin A ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A non-aqueous isocratic reversed-phase packed capillary high performance liquid chromatography method for the determination of retinyl esters, utilizing temperature programming and on-column focusing large volume injection, has been developed. The stationary phase material was C30, and the mobile phase consisted of acetonitrile-dichloromethane (70 : 30, v/v). A three-step temperature program, starting at 10°C for 10 min, then 1°/min to 30°C, and finally 2.5°/min to 70°C, was found most appropriate. Compared to an isothermal separation at 25°C, this temperature program provided improved peak resolution, enhanced peak shapes of the last eluting compounds, and a reduction of the overall elution time. A mass limit of detection of 27 pg was found with respect to retinyl palmitate, using UV detection with an “U” shaped flow cell at 327 nm. This corresponds to a concentration limit of detection of 2.7 pg/μL, when utilizing an injection volume of 10 μL. The concentration of retinyl palmitate in arctic seal liver samples was estimated to be 62.6 μg/g liver.
    Additional Material: 2 Ill.
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  • 130
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    Separation of Positional Isomers on A, C- and A,D-Bridged Calix[6]arene as Stationary Phases in Capillary GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 679-682 
    Details
    ISSN: 0935-6304
    Keywords: A,C- and A,D-bridged calix[6]arene ; stationary phase ; capillary gas chromatography ; geometric and positional isomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A,C-Bridged (ACCX) and A,D-bridged isopropyldimethylsilylcalix[6]arene (ADCX) dissolved in OV-1701 were used as stationary phases in isothermal capillary gas chromatographic separation of some positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated are well resolved on the two phases. Retention of all the solutes investigated is longer on ACCX than on ADCX. The longer retention on A,C-bridged calix[6]arene is probably due to extra inductive interactions of the solute molecule with the carbonyl moieties in the phase. Separation factors for closely eluting isomer pairs are similar on the two phases. This seems to indicate that the carbonyl moieties do not play an appreciable role in discriminating the isomer molecules on entering the cavity of the calixarene if the solute is retained by the inclusion process.
    Additional Material: 2 Tab.
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  • 131
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    Two-Dimensional Gas Chromatography. Concepts, Instrumentation, and Applications - Part 1: Fundamentals, Conventional Two-Dimensional Gas Chromatography, Selected Applications (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 647-665 
    Details
    ISSN: 0935-6304
    Keywords: Two-dimensional GC ; statistical method of overlap ; petroleum ; fuels ; enviromental samples ; organochlorine compounds ; flavors ; aromas ; foods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The writer of this review published in 1978 a three-part article on two-dimensional gas chromatography in the first three issues of this journal [1]. The review was written at a time when capillary column GC was still in its infancy. Commercial columns were (essentially) unavailable and sample introduction into capillary columns was done exclusively in the split mode. Two-dimensional separations were explored in only a few laboratories. The limitations of capillary column technology made this exercise rather difficult. The introduction of fused silica capillary columns in the early eighties drastically changed the landscape in which gas chromatography was practiced. It took the chromatographic community just a few years to convert from packed columns to capillary columns. Instrumentation and accessories specifically designed for capillary column use came onto the market. This writer had great hopes that the revolution in capillary column GC would be mirrored in the development of instrumentation for Two-Dimensional Gas Chromatography. This never materialized. On the contrary, tentative steps taken by a few manufacturers and suppliers of chromatographic equipment fizzled out. It was perhaps the introduction of relatively inexpensive and user friendly GC/MS instrumentation, in combination with nearly indestructible fused silica capillary columns that took away the incentive to develop commercially viable Two-Dimensional Gas Chromatography. Much of the thinking went like this: why insist on good chromatography if mass spectrometry can do the job without the need for complete separation. Some progress in the further development of conventional Two-Dimensional Gas Chromatography has certainly been made over the last 20 years but there has not been a great deal of excitement. Applications have also been relatively sparse and they are limited to just a few areas. Science does not remain static and chromatography is no exception. Progress in gas chromatography is driven by new technology and ideas. Substantial improvements in two-dimensional GC were not forthcoming until Phillips and his research group introduced and implemented an entirely new form of Two-Dimensional Gas Chromatography, called comprehensive two-dimensional GC, or GC×GC. This breakthrough occurred only in 1991 [2]. It does take some time before scientists change attitudes and habits. There is always a time lag between the introduction of new technology and its general acceptance. The public's attitude toward comprehensive Two-Dimensional Gas Chromatography is probably no exception. The number of scientists who are actively pursuing this new branch of gas chromatography is still very small. It is often a single individual who carries the torch. J.B. Phillips' name is synonymous with comprehensive Two-Dimensional Gas Chromatography. He is not only its inventor and proponent but his fertile mind has initiated research in other related areas. Sadly, he passed away shortly before this review was written. This contribution is dedicated to his memory.
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  • 132
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    Automated On-Line GPC-GC-FPD Involving Co-Solvent Trapping and the On-Column Interface for the Determination of Organophosphorus Pesticides in Olive Oils (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 17-23 
    Details
    ISSN: 0935-6304
    Keywords: Coupled GPC-GC ; gel permeation chromatography ; on-column interface ; co-solvent trapping ; gas chromatography ; large volume injection ; organophosphorus pesticides ; olive oil ; automation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The robustness of an automated on-line GPC-GC-FPD method for the determination of Organophosphorus (OP) Pesticides in olive oil has been significantly improved, now allowing a routine operation. The original GPC-GC transfer technique employed a loop type interface with an early vapor exit and co-solvent trapping. Shooting, caused by boiling delay and malfunctioning of the solvent vapor exit during the transfer of the 3 mL solvent fraction to the retention gap, resulted in insufficient focusing of the OP-pesticides. In this interfacing concept, the GPC fraction is introduced directly into the carrier gas stream during a certain time interval using the Dualchrom pressure- and flow regulation, resulting in a very stable transfer. The interface now basically corresponds to an on-column interface with flow regulation. Via a Pyrex glass door behind the GC-oven door it can be seen that the liquid flow is broken up into alternating gas-liquid segments by the carrier gas flow during transfer. This avoids shooting in the retention gap and broadens the temperature range for successful transfer. By using a smaller sized GPC column the solvent fraction transferred was reduced to 1.3 mL. Methyl acetate/cyclopentane and the co-solvent n-nonane were selected for their lower boiling points. The modified method is very robust and has been applied to the analysis of 28 different OP-pesticides in olive oil with an overall detection limit of 0.002 mg/kg. Routinely 24 h of unattended operation is possible with a cycle time of 75 min.
    Additional Material: 6 Ill.
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  • 133
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    Investigation into the Formation of Bubbles in Capillary Electrochromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 29-32 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; electroosmotic flow ; frit ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of bubbles in capillary electrochromatography (CEC) is well documented: possible origins include Joule heating and variations in EOF velocity on passing from the stationary phase through the frit and into the open tube. Methods for the prevention of bubble formation are discussed which are confirmed by experimental results. Using frit lengths varying from 1 mm to 6 mm it is shown how frit length is directly related to the likelihood of bubble formation and how this is affected by applied voltage. It is shown that the change in applied voltage across a capillary affects the formation of bubbles and also that rebonding octadecylsilane (ODS) onto the silica frit after formation of the frit can minimize the formation of bubbles and how this effects the chromatography. A method is also described for increasing the robustness of silica capillaries using a column coupler along with modifications made to conventional capillary electrophoresis equipment to cater for CEC.
    Additional Material: 4 Ill.
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  • 134
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    Determination of Dihydroxybenzenes in Plastic Food Packaging Materials and in Food Simulating Liquids Using Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 39-42 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; CE ; chemical migration ; food contact plastics ; dihydroxybenzenes ; packaging ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A capillary electrophoresis method has been developed to determine 1,2-dihydroxybenzene and 1,3-dihydroxybenzene in the food simulants distilled water, 3% acetic acid, 15% ethanol, and olive oil. Both substances, used as monomers and additives to make food packaging plastics, could be analyzed within 15 min. The 1,4-dihydroxybenzene isomer was unretained and eluted with the electroosmotic flow, and so the CE method can give only a semi-quantitative estimate of this isomer if it is present as a migrant. The analytical recovery for the 1,2- and 1,3-isomers from spiked simulants was good at 87% to 98% except for 1,2-dihydroxybenzene which could only be recovered to the extent of 58% from olive oil. Calibration graphs were linear and the limit of detection for each substance was 0.6 mg/kg, which is well below migration limits for these substances. It is concluded that CE offers a rapid and reliable analysis for the control of migration from plastics intended for food contact which employ 1,2-dihydroxybenzene or 1,3-dihydroxybenzene during manufacture, and offers a screening method for 1,4-dihydroxybenzene migration.
    Additional Material: 4 Ill.
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  • 135
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    Injection by Programmed Temperature Vaporization Injection (PTV) of Gaseous Samples for Gas Chromatography - Atomic Emission Spectrometry (GC-AED) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 47-51 
    Details
    ISSN: 0935-6304
    Keywords: Programmed temperature vaporization (PTV) ; GC-AED ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Programmed temperature vaporization injection (PTV) coupled to gas chromatography and atomic emission detector (AED) has been studied for large volume injection of gaseous samples. As examples of the effectiveness of the technique, the results of the analysis of a series of headspace samples of foods such as garlic and onion, and of landfill gases are presented. The volumes of gaseous samples reconcentrated varied from a few milliliters up to liters depending on analyte dilution, through focusing onto a sorbent trap, then rapid liberation into the GC-AED system by programmed thermal desorption. Despite the high carrier gas flow rates associated with direct PTV-GC, AED performance and sensitivity were unaffected. The detailed elemental information obtained from the PTV-GC-AED analyses was confirmed using a PTV coupled to a gas chromatograph with ion trap detector mass spectrometer as detector (PTV-GC-ITD/MS).
    Additional Material: 4 Ill.
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  • 136
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    Investigation into the Effects of Sample Dissolving Solvents and Sample Matrices on the Separations Obtained in Capillary Electrophoresis. Part II. MECC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 55-58 
    Details
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic capillary chromatography ; sample dissolving solvent ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 137
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    Separation of Regioisomers of Substituted Bromoindoles of Pharmaceutical Interest by RP-HPLC and Capillary Electrophoresis Based on Interaction with Sulfobutyl Ether-β-cyclodextrin (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 59-62 
    Details
    ISSN: 0935-6304
    Keywords: Sulfobutyl ether-β-cyclodextrin ; micellar electrokinetic chromatography ; separation of regioisomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
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  • 138
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    Determination of the Specific Migration of DEHP into Food Simulants Using High Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 70-72 
    Details
    ISSN: 0935-6304
    Keywords: HPLC ; di(2-ethylhexyl) phthalate ; migration ; foods and food simulants ; PVC cling film ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 139
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    Capillary Electrophoretic Identification of Commercial Gelling Agents (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 79-82 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; thickeners ; monosaccharides ; PMMA capillaries ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Gelling agents based on polysaccharides have become extremely important in the food industry. As more and more products like soups and sauces have become available in lyophilized form, thickeners have to be added to give a controlled consistency to the finished meal. A capillary electrophoretic method has been developed to investigate the monosaccharide composition of hydrolyzed thickeners. 2-Aminoanthracene was used as a derivatization reagent to allow sensitive fluorescence detection. This system was applied to a set of standard thickeners as well as to food samples.
    Additional Material: 5 Ill.
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  • 140
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    GC Analysis of Organic Acids and Phenols Using On-Line Methylation with Trimethylsulfonium Hydroxide and PTV Solvent Split Large Volume Injection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 83-88 
    Details
    ISSN: 0935-6304
    Keywords: Large volume injection ; programmed-temperature vaporizer ; organic acids ; phenols ; derivatization ; trimethylsulfonium hydroxide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The combination of on-line methylation using trimethylsulfonium hydroxide with large volume injection of 100 μL was evaluated for the analysis of organic acids and phenols in water. Solvent split injection was applied with complete evaporation of the solvent before analytes were transferred onto the GC column. Despite complete solvent removal, losses were very low compared to conventional splitless injection even for volatile acidic compounds such as propionic acid and phenol. This is explained by intermediate formation of low volatility trimethylsulfonium salts of the analytes which were held in the injector for long evaporation times of up to 10 min, if the evaporation temperature was as low as 10°C. Using a simple liquid/liquid extraction procedure, volatile fatty acids, dicarboxylic acids, benzoic acids and phenols could be detected in 5 mL of water at concentrations of 0.04-0.1 μmol/L with GC/MS in full scan mode. Lactic, pyruvic, and also malonic acids could only be detected at higher levels because of their limited extractability from water as well as their poorer methylation yields. The method provides an easy way to sensitively detect acidic compounds of medium to high volatility in water. It was applied for screening of organic acids and phenols in batch cultures of anaerobic bacteria of which one example is shown.
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  • 141
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    Study on the Performance of Three Different Capillary Gas Chromatographic Analyses in the Evaluation of Milk Fat Purity (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 97-102 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; milk fat purity ; chemometrics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The adulteration of milk fat with foreign fat has been and still is a major concern in the dairy industry. Milk fat purity is currently evaluated by triglyceride analysis by using the Official EU method. The detection limit of the various vegetable and animal fats ranges between 4 and 6%. This research was carried out to verify whether it is possible to decrease the detection limits of beef tallow, which is the most widely used adulterating animal fat. For this purpose, determinations of diglycerides and 3,5-cholestadiene, together with the Official EU method, were applied both to several samples of pure milk fat and to mixtures of milk fat with different percentages of beef tallow. The best results were obtained combining the data deriving from the three determinations by multivariate statistical techniques; in particular, the statistical model obtained by the UNEQ technique seems to be able to decrease the detection limit of beef tallow from 5.2 to 2%. The diglyceride and 3,5-cholestadiene evaluation, combined with the Official EU method for triglycerides, can be usefully applied both to detect small additions of beef tallow and to demonstrate the adulteration of milk fat samples showing results close to the detection limit of the official method.
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  • 142
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    Solid-phase Microextraction of Volatile Polar Compounds in Water (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 109-115 
    Details
    ISSN: 0935-6304
    Keywords: Solid-phase microextraction ; capillary gas chromatography ; volatile polar compounds ; water matrix ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method was developed for the analysis of volatile polar compounds in a water matrix using open cap vials Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC). Both SPME techniques - direct sampling and headspace - were tested. Optimization of experimental conditions - exposure time, desorption time, with headspace SPME in addition the influence of the temperature and ionic strength of the sample solution on compound sorption, and finally GC response - were investigated. The analytes were extracted by directly immersing the 85 μm polyacrylate fiber in the aqueous sample or in the headspace. The linear range of the preconcentration process and the precision were examined. The amount of polar analytes sorbed on the fiber was determined and was found to be concentration dependent; it amounted to 0.014-0.64% in the concentration range of 0.00425-425 ppm studied in aqueous solution for direct sampling SPME and to 0.011-2.76% for solutions of concentration 0.0425-255 ppm for headspace SPME. The limits of determination were ascertained. Headspace SPME was applied to the analysis of real-life samples.
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    Analysis of Aliphatic Amines by Micellar Electrokinetic Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 126-128 
    Details
    ISSN: 0935-6304
    Keywords: Micellar electrokinetic chromatography ; capillary electrophoresis ; amines ; cyclodextrins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 144
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    Drug Monitoring in Human Plasma by Capillary Gas Chromatography Coupled with Atomic Emission Detection. Potential and Limitations (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 123-125 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography (GC) ; atomic emission detection (AED) ; human plasma ; drug monitoring ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 145
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    Development and Validation of a Reversed-Phase Liquid Chromatographic Method for Analysis of Theophylline in Human Plasma (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 131-132 
    Details
    ISSN: 0935-6304
    Keywords: RP-HPLC ; theophylline ; asthma ; apnea ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    Semi-continuous High Speed Gas Analysis of Generated Vapors of Chemical Warfare Agents (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 153-158 
    Details
    ISSN: 0935-6304
    Keywords: Vapor analysis ; nerve agents ; sulfur mustard ; data acquisition ; automation ; valve injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method is presented for the continuous analysis of generated vapors of the nerve agents soman and sarin and the blistering agent sulfur mustard. By using a gas sampling valve and a very short (15 cm) column connected to an on-column injector with a “standard length” column, the system can either be calibrated or used for performing high speed gas analyses. When using a flame ionization detector, the detection limit was ca. 100 ppb (ca. 0.5-1.0 mg/m3). This technique is applied in inhalation toxicokinetic studies of nerve agents and mustard gas in the guinea pig.
    Additional Material: 6 Ill.
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  • 147
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    Capacity of Uncoated 0.53 mm i.d. Pre-Columns for Retaining Sample Liquid in the Presence of a Solvent Vapor Exit (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 149-152 
    Details
    ISSN: 0935-6304
    Keywords: Large volume on-column injection ; flooded zone ; capacity of 0.53 mm i. d. precolumns ; solvent trapping ; solvent vapor exit ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---0.53 mm i. d. uncoated precolumns of about 10 m in length followed by a solvent vapor exit have become a standard set-up for large volume on-column injection. It went unnoticed, however, that the introduction of a vapor exit requires two modification of previous working guidelines. First, the capacity of the precolumn to retain sample liquid is increased by a factor of 2.3-3 as a result of the around 100 times higher carrier gas flow rate. Secondly, it must be considered that this gain in retention of liquid is lost again upon closure of the exit: as the gas flow rate is reduced to a few mL/min, the layer of the residual sample liquid expands about 2.3-3 times. Hence, closure should occur late, and a section of the precolumn must be assigned for this secondary spreading.
    Additional Material: 3 Ill.
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  • 148
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    Electronic Resource
    Large Surface Area Divinylbenzene Copolymers for Size Exclusion Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 63-66 
    Details
    ISSN: 0935-6304
    Keywords: Divinylbenzene copolymers ; exclusion limit ; size exclusion chromatography ; surface area ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 149
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    Electronic Resource
    A New Cell for Single Sided Headspace Sampling and Evaluation of Barrier Function in Laminated Paperboard (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 164-170 
    Details
    ISSN: 0935-6304
    Keywords: Food packaging ; functional barrier ; gas chromatography ; laminated paperboard ; mass spectrometry ; single sided headspace ; paperboard ; plastic film ; polymer film ; test cell ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new cell for single sided headspace sampling has been developed for the analysis of volatile organic compounds from food packaging paperboard and laminated paperboard. The cell, which samples the volatile organic compounds over a selected surface, is useful for determining the barrier function of laminated paperboards with respect to volatile compounds. The analysis of volatile organic compounds is carried out by purge and trap capillary gas chromatography in combination with mass spectrometric detection and compound identification. The new sampling cell was constructed to facilitate specific analysis of organic compounds from only one side of a laminated paperboard. The construction and the operating principles of the new sampling device are described. The repeatability of the single sided headspace procedure was found to be quite good. Relative standard deviations of about 5-7% were obtained for the major compounds quantified in replicate headspace analyses of a laminated paperboard. The volatile compounds released from the inner side of a food packaging paperboard sample with different surface composition on the two sides were determined. The barrier function against volatile organic compounds of some laminated paperboards was investigated employing the new headspace cell.
    Additional Material: 7 Ill.
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  • 150
    Electronic Resource
    Electronic Resource
    HPLC Control of an Alkyl Glycoside Synthesis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 188-190 
    Details
    ISSN: 0935-6304
    Keywords: LC stationary phases ; porous graphitic carbon ; surfactant ; alkyl glycosides ; glycosides ; evaporative light scattering detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
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  • 151
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    Quantitative Determination of BTEX and Total Aromatic Compounds in Gasoline by Comprehensive Two-Dimensional Gas Chromatography (GC×GC) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 195-200 
    Details
    ISSN: 0935-6304
    Keywords: Multi-dimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; GC×GC ; BTEX ; aromatics ; reformulated gasoline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Comprehensive two-dimensional gas chromatography (GC×GC) has been applied to the quantitative analysis of benzene, toluene, ethylbenzene, xylenes (BTEX), and all heavier aromatic compounds in gasoline. The two-dimensional chromatographic separation used volatility selection on the first-dimension column and polarity selection on the second-dimension column. In the resulting GC×GC chromatogram, aromatic species were resolved from other compound classes. Moreover, structurally related aromatics were grouped in a manner that facilitated identification and integration. The response of a flame ionization detector to each major aromatic group in gasoline was calibrated using internal standards. Quantitation produced results directly comparable with ASTM standard methods. The present GC×GC method can be expanded to analyze other gasoline components.
    Additional Material: 1 Ill.
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  • 152
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    Electronic Resource
    Membrane Extraction Combined with Thermodesorption/Gas Chromatography and Mass Selective Detection for the Analysis of Volatile Organic Compounds in Water (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 205-212 
    Details
    ISSN: 0935-6304
    Keywords: Membrane extraction ; hollow fiber membrane ; thermodesorption ; GC-MS ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The range of application of a commercial thermodesorption-cryofocussing unit connected to a gas chromatograph/mass selective detector was extended to water analysis by using it in conjunction with membrane extraction. A flow of nitrogen passes through a silicone hollow fiber immersed in the water sample and extracted volatile organic compounds are enriched in a sorption tube mounted on top of the extraction cell. The sorption tube is then placed in the thermodesorption unit and analyzed by GC/MS. The optimal extraction parameters of this combined method were found to be 30 min extraction at 20°C with a stirring speed of 1,250 rpm and a flow rate of 100 mL/min nitrogen using a silicone hollow fiber of 0.3 m length. Under these conditions the reproducibility of the method was 5.2-10.5% RSD. The linear dynamic range of the optimized method spans three orders of magnitude and detection limits were found to be 0.02-0.1 μg/L for cis/trans-1,2-dichloroethene, benzene, trichloroethene, chlorobenzene, bromobenzene, ethylbenzene, 1,1,2,2-tetrachloroethane, and 1,2/1,4-dichlorobenzene. The method was found to be suitable for compounds with boiling points up to 220°C as memory effects increased considerably from dichloro- to hexachlorobenzene. Highly contaminated groundwater samples were analyzed. Quantitative results corresponded well with those achieved with conventional headspace-GC/FID.
    Additional Material: 10 Ill.
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  • 153
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    Determination of Phenolic Compounds in Artemisia capillaris (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 222-224 
    Details
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography ; Artemisia capillaris ; phenolic compounds separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 154
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    Electronic Resource
    New Stationary Phase Prepared by Immobilization of a Copper-Amine Complex on Silica and Its Use for High Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 103-108 
    Details
    ISSN: 0935-6304
    Keywords: HPLC ; stationary phase ; copper-amine complex ; aromatic amines ; polyaromatic hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Chromatographic silica (10 μm) was chemically modified with the silylating agent: [3-(2-aminoethyl)aminopropyl]trimethoxysilane (AEAPTS). The reaction product was characterized by elemental analysis and infrared and 13C and 29Si NMR spectra. The chemically modified silica was treated with Cu(II) in methanol medium. This cation was strongly adsorbed through complexation by the pendant ethylenediamine groups attached to the silica surface. The complex formed on the silica surface was shown to be stable in both aqueous and non-aqueous media. The aim of Cu(II) immobilization is to use this new material as a stationary phase in High Performance Liquid Chromatography (HPLC). Separations of synthetic mixtures of aromatic amines and of polyaromatic hydrocarbons were undertaken using 150×3.9 mm HPLC columns packed with the modified silica, with and without copper ions, to follow the influence of the cation on the chromatographic separation and to verify the efficiency of the new stationary phase for HPLC.
    Additional Material: 6 Ill.
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  • 155
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    Electronic Resource
    The Influence of Liner Dimensions on Injector Band Broadening in Split Injections in Fast Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 116-118 
    Details
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; peak band broadening ; packed capillary columns ; narrow-bore columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 156
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    High Performance Liquid Chromatographic Screening and Gas Chromatography-Mass Spectrometry Confirmation of Tebuthiuron Residues in Drinking Water (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 239-241 
    Details
    ISSN: 0935-6304
    Keywords: Tebuthiuron ; GC-MS ; HPLC ; drinking water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 157
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    Suppressed Ion Chromatographic Determination of Chloride in Concrete (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 245-246 
    Details
    ISSN: 0935-6304
    Keywords: Chloride ; suppressed ion chromatography ; concrete ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 158
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    Comprehensive Two-Dimensional Gas Chromatography with Mass Spectrometric Detection (GC × GC/MS) Applied to the Analysis of Petroleum (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 251-255 
    Details
    ISSN: 0935-6304
    Keywords: Multi-dimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; GC × GC ; mass spectrometry ; petroleum ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Comprehensive two-dimensional gas chromatography coupled with mass spectrometric detection (GC × GC/MS) is a three-dimensional analytical method. In its application to petroleum analysis, the high peak capacity of GC × GC produced chromatographic resolution of over 750 peaks from a marine diesel fuel. The MS detector provided a full-scan mass spectrum for each resolved peak. The integration of an MS detector with GC × GC provides increased capability to identify minor components, determine members of homologous series, and characterize ordered peak patterns of related components that are visible in the GC × GC chromatogram.
    Additional Material: 4 Ill.
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  • 159
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    Electronic Resource
    An Unexpected Molecular Imprinting Effect for a Polyaromatic Hydrocarbon, Anthracene, Using Uniform Size Ethylene Dimethacrylate Particles (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 256-260 
    Details
    ISSN: 0935-6304
    Keywords: Molecular imprinting ; PAH ; molecular recognition ; selectivity ; redox polymerization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A non-covalent type of molecular imprinting effect toward a polyaromatic hydrocarbon (PAH), viz. anthracene, was studied utilizing uniformly sized ethylene dimethacrylate (EDMA) polymer particles without functional host monomers. Although polymerization at 0°C initiated by a redox initiation system was expected to afford larger molecular imprinting effect due to stronger and more effective intermolecular interaction between the template and surface functional groups of the polymer, almost no imprinting effect was observed, while a much higher polymerization temperature of 70°C unexpectedly afforded a larger molecular imprinting effect for the template anthracene. In order to determine the unexpected imprinting effects observed, uniformly sized, macroporous un-imprinting EDMA polymer particles (base particles) were prepared by various polymerization techniques at different polymerization temperature as well as with different initiation systems. The careful studies proved that each kind of base polymer particle showed different molecular recognition ability, especially toward anthracene, which is depends upon the physical properties of each kind of base polymer particle. On the basis of these facts, we would propose that the potential molecular recognition ability of the un-imprinted base polymer particles is another important factor for realization of effective molecular imprinting alongside the factors reported previously.
    Additional Material: 4 Ill.
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  • 160
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    Electronic Resource
    Analysis of Cyclic Organic Carbonates with Chromatographic Techniques. Part 1: Ethylene Carbonate and Glycerol Carbonate (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 276-278 
    Details
    ISSN: 0935-6304
    Keywords: Cyclic carbonates ; thermal stability ; chemical stability ; gas phase chromatography ; liquid phase chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 161
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    Improved Modification of a Laser Light-Scattering Detector for Use in Packed Capillary High Temperature Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 283-286 
    Details
    ISSN: 0935-6304
    Keywords: Evaporative light scattering detection ; capillary nebulizer ; packed capillary ; columns ; high temperature liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 5 Ill.
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  • 162
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    Electronic Resource
    Rapid Method for the Determination of Thiabendazole and Imazalil Residues in Orange by Capillary Column Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 303-304 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; food analysis ; pesticide residues ; thiabendazole ; imazalil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
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  • 163
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    Methodology for the Determination of Cocoa Butter Replacements in Chocolate by Triacylglycerol GC Analysis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 305-307 
    Details
    ISSN: 0935-6304
    Keywords: High temperature gas chromatography ; chocolate analysis ; triacylglycerols determination ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Tab.
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  • 164
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    Transition Metal-Mediated Separation of Isomeric Pneumocandins by Capillary Electrochromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 309-314 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; isomers ; pneumocandins ; separation ; transition metal ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The novel separation of a 3-hydroxyproline containing a semi-synthetic macrocyclic antifungal agent from its structurally related 4-hydroxyproline isomer using capillary electrochromatography (CEC) is described. The molecular weight of the two compounds is 1093 Daltons and they differ only in the placement of a proline -OH group. The separation is achieved using capillaries packed or coated with ODS particles (C18) or with glycerol bound to silica through a carbon chain linker. The presence of a transition metal (Ni(II), Ag(I), Zn(II), or Cu(II)) as buffer additive in the phosphate buffer (pH=2.5):CH3CN (75:25, v/v) is essential to achieve a baseline separation. HPLC columns packed with similar ODS particles showed no selectivity. Capillaries packed or coated with C18 material under similar conditions showed partial selectivity compared to the glycerol capillaries. Some fundamental aspects of CEC, such as capillary temperature, applied voltage, and buffer composition were varied in order to study the mechanism of the separation. This mechanistic study included the testing of first and second row transition metal ions (individually or in combination), the use of organic solvents, the use of an ion pair reagent, and the use of β- and γ-cyclodextrin to assess the impact on the separation. The resolution was dependent on the metal ion concentration and is consistent with a mechanism of metal-oxygen complexation through the hydroxyl groups of the two isomers and glycerol.
    Additional Material: 4 Ill.
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  • 165
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    Improvement of the Chemometric Variety Characterization of Wines by Improving the Detection Limit for Aroma Compounds (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 322-326 
    Details
    ISSN: 0935-6304
    Keywords: Solid phase microextraction (SPME) ; capillary gas chromatography ; detection limits ; wine aroma compounds ; classification of wines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Headspace-SPME followed by capillary gas chromatography/mass spectrometry was used to investigate 90 German wines originating from different grape varieties, vintages, and growing areas. Aromagrams obtained in single ion monitoring (SIM) and in the full scan detection mode (SCAN) of quadrupole mass spectrometer were compared. Detection limits, reproducibility, and linearity for some aroma relevant substances were estimated over a wide concentration range. The advantages of SIM data set (lower detection limit, better reproducibility and linearity in the smaller concentration ranges) should be reflected in more reliable results in classification of wines. To verify these expectation, classification of variety by discriminant analysis was performed with cross validation using both SIM and SCAN data sets including 19 aroma compounds, respectively.
    Additional Material: 4 Ill.
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  • 166
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    Improvement of the Detection Limit in Capillary Gas Chromatographic Trace Analysis of C2-C4 Hydrocarbons by Post Column Cryogenic Trapping (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 335-338 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC trace analysis of C2-C4 hydrocarbons ; signal-to-noise ratio, improvement ; post column cryogenic trapping ; thermal remobilization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method for the improvement of signal-to-noise ratios and hence detection limits in capillary gas chromatographic trace analysis of C2-C4 hydrocarbons was developed. It is based on the post column cryogenic trapping of the separated hydrocarbons using liquid nitrogen as coolant and its fast reinjection into the detector by rapid heating of the capillary tubing used for trapping. The improved signal-to-noise ratios were applied to decrease the sample volume and/or to lower the detection limit 10 to 27 times. The concentrations of these hydrocarbons in an urban air sample determined without and with post column cryogenic trapping were in good agreement but the precision was better when applying the cryogenic trapping mode.
    Additional Material: 3 Ill.
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  • 167
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    Multidimensional Capillary GC-GC for the Analysis of Real Complex Samples. Part IV. Enantiomeric Distribution of Monoterpene Hydrocarbons and Monoterpene Alcohols of Lemon Oils (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 350-356 
    Details
    ISSN: 0935-6304
    Keywords: Multidimensional GC ; enantioselective gas chromatography ; lemon oil ; monoterpene hydrocarbons ; monoterpene alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper describes a fully automated, multidimensional, double-oven GC-GC system, developed in our laboratory. The system is based on the use of mechanical valves which allow the multitransfer of different fractions during the same GC analysis and the use of the two GC independently when the multitransfer options is not used. Pneumatic and electronic circuits permit maintenance of constant retention times in the pre-column, even for the components eluted after numerous transfers. The system has been used for the determination of the enantiomeric distribution of β-pinene, sabinene, limonene, linalol, terpinen-4-ol, and α-terpineol in lemon oils. The results obtained allowed the characterization of cold-pressed lemon oils.
    Additional Material: 3 Ill.
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  • 168
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    Effect of Injector Conditions on the Reproducibility of Gas Chromatographic-Electron Capture Detection of Sterol Derivatives and Synthetic Pyrethroids (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 362-366 
    Details
    ISSN: 0935-6304
    Keywords: Pentafluorophenyldimethylsilyl (flophemesyl) chloride ; split and splitless injection ; derivatised sterol analysis ; synthetic pyrethroids ; injector liner activity ; gas chromatographic electron capture detection ; multidimensional gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 169
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    Sweeping with an Enhanced Electric Field of Neutral Analyte Zones in Electrokinetic Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 367-372 
    Details
    ISSN: 0935-6304
    Keywords: Sweeping ; sample stacking ; micellar electrokinetic chromatography (MEKC) ; retention factor (k) ; sample matrix ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept of sweeping has been used in electrokinetic chromatography to explain the concentrating mechanism in micellar electrokinetic chromatography when the sample matrix is a high resistivity non-micellar aqueous solution. Theoretical and experimental studies were undertaken. It was found that the total focusing effect is brought about by the cumulative effect of sweeping and sample stacking. For better analytical results, compounds showing low to moderate retention factors (k) and compounds showing high values of k must be dissolved in low and high conductivity matrices, respectively.
    Additional Material: 4 Ill.
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  • 170
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    Simultaneous Determination of Inorganic Anions and Organic Acids in Environmental Samples by Capillary Zone Electrophoresis with Indirect UV Detection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 379-385 
    Details
    ISSN: 0935-6304
    Keywords: CZE ; indirect UV detection ; anions and organic acids ; environmental samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary zone electrophoresis (CZE) with indirect UV detection was developed for the simultaneous determination of inorganic anions and organic acids in environmental samples. Various aromatic acids (benzoic, phthalic, trimellitic, and pyromellitic acids) were evaluated as background electrolytes (BGEs) to give high resolution and detection sensitivity. Co-electroosmotic conditions such as the concentration of BGE, electrolyte pH, and EOF modifier were systematically investigated. Three inorganic anions and ten organic acids were determined simultaneously in 10 min using an electrolyte containing 10 mM phthalic acid, 0.5 mM myristyltrimethylammonium bromide (MTAB), and 5% methanol (MeOH) (v/v) at pH 5.60. Linear plots for the test solutes were obtained in the concentration range 0.01-1.0 mM with detection limits in the range 5-30 μM. The proposed method was successfully demonstrated for the determination of inorganic anions and organic acids in natural water, soil, and plant extracts after direct sample injection.
    Additional Material: 7 Ill.
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  • 171
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    Pulsed Splitless Injection and the Extent of Matrix Effects in the Analysis of Pesticides (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 395-402 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; pulsed splitless injection ; pesticide residues ; matrix effects ; retention gap ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The applicability of pulsed splitless injection to the gas chromatographic analysis of pesticide residues in fruit and vegetables has been evaluated. 22 pesticides belonging to different chemical classes, including those known to be liable to matrix induced response enhancement, were selected for the study. The parameters of pressure pulse have been tested for optimum performance of injection. Application of the pressure pulse was found to decrease matrix effects during analyses of real samples. Further decline of matrix effects was obtained using higher sample injection volumes. The installation of a deactivated retention gap was necessary to obtain good peak shapes with injection volumes exceeding 1 μL of sample. Up to 4 μL was then injected without peak distortion and consequent loss of resolution. Using 4 μL pulsed splitless injection, matrix effects were almost completely eliminated even at very low concentration levels of analytes. The highest matrix effects observed for tested compounds at the lowest concentration level tested were in the range of 110-122%.
    Additional Material: 3 Ill.
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  • 172
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    Theory of Fast Capillary Gas Chromatography - Part 3: Column Performance vs. Gas Flow Rate (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 403-413 
    Details
    ISSN: 0935-6304
    Keywords: Constant length optimization ; constant efficiency optimization ; efficiency-optimized flow rate ; fast GC ; film inefficiency factor ; high pressure drop ; speed-optimized flow rate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: At the high pressure drop required for the fast analysis of complex mixtures, the equations for the column plate height, H, and plate duration, Q, as functions of the carrier gas velocity, u, differ substantially from the equations for the same quantities expressed via the carrier gas flow rate, F. While u as an independent pneumatic variable is more convenient for the theoretical studies, F is a more convenient as a control parameter in practical applications. Equations for H vs. u and for Q vs. u from Parts 1 and 2 are transformed here into expressions for H vs. F and Q vs. F. An efficiency-optimized flow rate (EOF) and a speed-optimized flow rate (SOF) are found. Expressions for these two quantities are considerably simpler than their velocity-based counterparts. In particular, SOF does not depend on column length, film thickness, and pressure drop.
    Additional Material: 3 Ill.
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  • 173
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    Temperature-Dependence of Supported-Liquid-Membrane Extraction (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 417-420 
    Details
    ISSN: 0935-6304
    Keywords: Sample preparation ; nitrophenols ; PCP ; 2,4-D ; liquid chromatography ; supported-liquid-membrane extraction ; environmental monitoring ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 4 Ill.
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  • 174
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    Total p-Chlorophenol Determination in Urine Samples of Subjects Exposed to Chlorobenzene, Using SPME and GC-MS (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 427-428 
    Details
    ISSN: 0935-6304
    Keywords: p-Chlorophenol ; urine ; SPME ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 175
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    A Fast and Reliable Method for the Determination of Anionic Impurities and Neutralization Agents in Electrodipcoats Using Capillary Zone Electrophoresis with Conductivity Detection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 297-299 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; conductivity detection ; inorganic anions ; organic acids ; electrodipcoats ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 176
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    Electronic Resource
    Supercritical Fluid Extraction and Supercritical Fluid Chromatography of Vitamin E in Pharmaceutical Preparations (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 300-302 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical-fluid-extraction ; supercritical-fluid-chromatography ; vitamin E ; pharmaceuticals ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract
    Additional Material: 1 Ill.
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  • 177
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    Teicoplanin-Based Enantiomeric Separations in CZE Using a Partial Filling Technique (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 315-321 
    Details
    ISSN: 0935-6304
    Keywords: Glycopeptide antibiotics ; chiral selectors ; Teicoplanin ; enantioseparations ; CZE ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Baseline separation of the enantiomers of a number of negatively charged amino and mandelic acid derivatives was achieved in less than 10 min by capillary electrophoresis in a polyacrylamide coated capillary, using the “partial filling method” (PFM) with submillimolar concentration of Teicoplanin (TE) as the chiral selector. The influence of the charge and concentration of TE, electrolyte solution composition and pH, on the enantioresolution was examined. Further proofs were brought to corroborate the hypothesis that the enantiorecognition takes place at the D-Ala-D-Ala binding site, whose blockade is responsible for the antibacterial activity of glycopeptide antibiotics. While the dependence of the chiral recognition capabilities of TE on electrolyte solution composition and pH could limit its applicability, improved sensitivity, reduction of TE wall adsorption, resulting in a good efficiency, and high cost reduction, due to the very small amount of chiral selector required, were shown as advantages of the PFM adopted in this study.
    Additional Material: 6 Ill.
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  • 178
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    Electronic Resource
    Solvent Trapping during Large Volume Injection with an Early Vapor Exit. Part 3: The Main Cause of Volatile Component Loss during Partially Concurrent Evaporation (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 327-334 
    Details
    ISSN: 0935-6304
    Keywords: Large volume on-column injection ; partially concurrent solvent evaporation ; solvent trapping ; retaining precolumn ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---When 0.53 mm i.d. uncoated precolumns connected to a solvent vapor exit are used for sample introduction with partially concurrent solvent evaporation, substantial losses of volatile solutes are often observed. They were found to be the consequence of solute accumulation at the front end of the flooded zone, which in turn is the result of a strong pressure drop over the flooded zone owing to the formation of plugs of sample liquid. The pressure drop causes significant solvent evaporation at the front, which enriches the solute material there and causes its loss. The use of 0.32 mm i.d. restrictions between the uncoated precolumn and the vapor exit greatly reduced this problem.
    Additional Material: 10 Ill.
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  • 179
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    Electronic Resource
    Separation of Chlorophylls and Their Degradation Products using Packed Column Supercritical Fluid Chromatography (SFC) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 339-342 
    Details
    ISSN: 0935-6304
    Keywords: Chlorophyll ; SFC ; supercritical fluid chromatography ; vegetables ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Complex mixtures of chlorophyll degradation products may arise during processing and storage of vegetable oil and green plant materials like broccoli and spinach. Determination of these compounds is important in the area of food chemistry. Therefore a method using packed column supercritical fluid chromatography (SFC) has been developed. The method comprises chromatography using a simple gradient of methanol in carbon dioxide at constant column back pressure of 30 MPa and a column temperature of 40°C. Effects of pressure and mobile phase composition showed the importance of applying a modifier gradient for optimal separation of the chlorophyll products. The method permits separation of 15 chlorophyll derivatives including chlorophyll a and b, pheophytins, and pyropheophytins on a C18 column in about 20 minutes. Identifications of the individual peaks were based on reference compounds, the retention order of the compounds, and their absorption spectra.
    Additional Material: 5 Ill.
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  • 180
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    HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana, and in Vitro Evaluation of Its Antioxidant Activity (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 343-349 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; gas chromatography-mass spectrometry ; essential oil analysis ; Lepechinia schiedeana ; antioxidant activity ; lipid peroxidation ; Ledol; Ledol HMQC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO2) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C15H26O, was the major constituent (20.04-36.87%) in all extracts. Oxygenated sesquiterpenes (24.36-43.14%), C10H16, monoterpenes (27.70-39.87%), and C15H24, sesquiterpenes (10.04-22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (Cn 〉 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.
    Additional Material: 4 Ill.
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  • 181
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    Use of Isopropanol as a Modifier in a Hexane-Acetonitrile Based Mobile Phase for the Silver Ion HPLC Separation of Positional Isomers of Triacylglycerols Containing Long Chain Polyunsaturated Fatty Acids (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 357-361 
    Details
    ISSN: 0935-6304
    Keywords: Silver ion HPLC ; long chain polyunsaturated fatty acid ; isopropanol ; separation of positional isomers ; degree of unsaturation ; normal phase retention effect ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A high resolution approach to silver ion HPLC was studied for the separation of positional isomers of triacylglycerols (TAGs) containing long chain polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA) in enzymatically synthesized structured TAGs. Isopropanol was used as a novel modifier in a hexane-acetonitrile based mobile phase for silver ion HPLC. Peak identification was based on HPLC-mass spectroscopy and selectivities of lipases. Positional isomers of TAGs containing one molecule of EPA, DHA, or DPA with saturated fatty acids (FAs) such as caprylic acid and palmitic acid were separated within 13 min using a gradient of hexane-isopropanol-acetonitrile as mobile phase. TAGs containing two or more EPA, DHA, or DPA were also separated from each other within 25 min, but their positional isomers were unresolved. The retention characteristics of the TAG were found to be related to the number of carbon atoms in the FAs present in addition to the number of double bonds and their isomeric configuration. One isomer with an unsaturated FA in the sn-2 position eluted faster than the other with the unsaturated FA in the sn-1 or 3 position. Species with longer chain FAs attached to TAGs with the same degree of unsaturation eluted faster than those that have shorter chain FAs. For example, docosapentaenoylhexadecanoyloctanoin (DPA/C16/C8) was eluted faster than dioctanoyldocosapentaenoin (DPA/C8/C8).
    Additional Material: 2 Ill.
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  • 182
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    A Computer Method for Predicting the Electrophoretic Mobility of Peptides (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 373-378 
    Details
    ISSN: 0935-6304
    Keywords: Electrophoresis ; electrophoretic mobilities ; CZE ; MEKC ; peptides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A computer model is presented for the prediction of the electrophoretic mobilities of peptides from physical constants derived from their amino acid sequences. The model assumes that the electrophoretic mobility can be represented by a product of four functions according to the relation:  lcomp= l(L)w(W)q(Q)c(CC), where L (a length parameter) is represented by the number of amino acid residues of the peptide, W (a width parameter) is represented by the average residue mass, Q = the charge of the peptide, and CC = the position of the center of charge relative to the center of mass. The model was used to calculate the electrophoretic mobilities of peptides in a 50 mM phosphate buffer at pH 2.5. Sixty-four test peptides ranging in size from 2 to 39 amino acid residues were used for this study. The calculated mobilities show excellent correlation with experimental measurements with a correlation coefficient greater than 0.98.
    Additional Material: 5 Tab.
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  • 183
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    Simultaneous Measurement of Hydrocarbons and Sulfur Compounds using Flame Ionization and Sulfur Chemiluminescence Detection for Sulfur Simulated Distillation (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 386-390 
    Details
    ISSN: 0935-6304
    Keywords: Sulfur chemiluminescence detection ; sulfur simulated distillation ; boiling point distribution ; simultaneous FID/SCD analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic system for the simultaneous acquisition of hydrocarbon and sulfur chromatograms was developed. Detection of sulfur compounds is achieved using a sulfur chemiluminescence detector (SCD) mounted in series with a flame ionization detector (FID). A constant fraction of the effluent of the FID is transferred to the SCD by means of a fixed restrictor. Unlike previous versions of this approach, the FID is not used to generate the chemiluminescent sulfur species. Rather, the FID is operated under optimum conditions for hydrocarbon analysis and a furnace is used to generate the chemiluminescent sulfur species. The system permits dual acquisition of the hydrocarbon and sulfur signals in a single analysis with a single column, since the detectors are operated in a serial fashion. The application of sulfur simulated distillation using this approach was examined, since this requires simultaneous universal and sulfur selective detection. Precision of absolute response of both the FID and SCD was typically less than 2% RSD for a standard reference material.
    Additional Material: 3 Ill.
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  • 184
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    A Novel Interface for Optimized Coupling of Gas Chromatography and Supersonic Jet Spectroscopy (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 391-394 
    Details
    ISSN: 0935-6304
    Keywords: REMPI-TOFMS ; laser mass spectrometry ; supersonic jet ; GC-MS ; interface ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The laser-based methods Laser Induced Fluorescence (LIF) and Resonance-Enhanced Multi-Photon Ionization (REMPI) can be used as highly selective detection modes for gas chromatography (GC). One major prerequisite for successful application of these detection methods is the availability of appropriate and reliable interfaces between the GC effluent and the molecular beam inlet. When a pulsed supersonic molecular beam (jet) source is used, the analyte molecules are efficiently cooled, allowing maximum selectivity of the laser spectroscopic detection methods. However, several technical problems have to be solved for practical realization of a GC-supersonic jet valve hyphenation. The pulsed jet interface should not interfere with the GC properties and the supersonic molecular beam properties. Further a good working cycle for the conversion from the continuously flowing GC current to the pulsed jet gas flow should be attained. This paper presents a novel setup of a GC-pulsed jet interface. The construction allows temporal and spatial compression of the analyte molecules in jet gas pulse and thus an increase of the detection sensitivity. Moreover, the GC effluent comes into contact only with glass surfaces and not with valve parts like plungers and seals. This reduces memory effects and sample decomposition. The valve setup is tested with a REMPI-TOFMS instrument.
    Additional Material: 2 Ill.
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  • 185
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    Selective Determination of Se4+ and Se6+ Using SPME and GC/MS (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 414-416 
    Details
    ISSN: 0935-6304
    Keywords: Selenium ; water ; SPME ; GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A method for the selective determination of Se4+ and Se6+ using solid phase microextraction (SPME) and GC/MS analysis is presented. Se4+ is selectively derivatized by reaction with 4,5-dichloro-1,2-phenylenediamine to form the corresponding piazselenolo complex, extracted by the SPME fiber, and determined by GC/MS. The RSD at a 5 μg/L concentration was 9.88% and the theoretical detection limit 6 ng/L. The method was employed to test real matrices; tap and river water were analyzed before and after spiking giving a recovery rate of 102% in river water and 97% in tap water.
    Additional Material: 3 Ill.
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  • 186
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    Determination of Vapor Liquid Equilibrium from the Kovats Retention Index on Dimethylsilicone using the Wilson Mixing Model (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 565-588 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Kovats retention index ; vapor pressure ; boiling point ; Wilson activity coefficient ; binary phase diagrams ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Non-ideal mixing in a dimethylsilicone stationary phase is modeled according to the Wilson activity coefficient. Pure liquid vapor pressures of alkylated compound series are calculated from capillary GLC retention with the functional group heat of solution in a polymer solvent. The new method uses the Kovats index, molar mass, and functional group to determine the bubble line of a compound. Boiling points at reduced and normal pressure are compared to literature values of 194 gasoline components. An unlike molecular pair interaction parameter is derived, using only bubble line data of the pure liquids. Binary phase diagrams are constructed and compared to vapor liquid equilibrium data.
    Additional Material: 22 Ill.
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  • 187
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    A Strategy for the Simplification and Solution of Complex Chromatographic Analysis Problems Utilizing Two-Dimensional Mapping of Retention Indexes Followed by Computer Modeling of Heart Cuts from Serially Coupled Columns Containing Different Stationary Phases (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 589-593 
    Details
    ISSN: 0935-6304
    Keywords: Computer modeling of GC ; computer simulation of GC ; computer-assisted GC analysis ; GC multicolumn analysis ; heart cutting GC analysis ; computer-assisted column design ; computer-assisted selectivity tuning ; retention index mapping ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The analysis of four components in a mixture containing many possible interferents is simplified by heart-cutting serially connected columns containing stationary phases of widely different polarities. The design of the proper lengths of the two columns and timing the heart-cuts is accomplished with the aid of a computer simulation of the problem. The computer program calculates the proper lengths of column to produce the shortest analysis time and also outputs the predicted chromatograms from both columns. The chromatogram from the first column is used to construct the timing gates for the heart-cuts and the chromatogram from the second or analytical column is used to set integration gates for the selected compounds of interest.
    Additional Material: 7 Ill.
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  • 188
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    Indirect Fluorimetric Detection of Cyclodextrins via Postcolumn Mixing with 2-p-Toluidinyl-6-naphthalenesulfonate in Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 609-612 
    Details
    ISSN: 0935-6304
    Keywords: Cyclodextrins ; 2-p-toluidinyl-6-naphthalenesulfonate ; indirect fluorimetric detection ; liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclodextrins (CD's) were visualized by postcolumn mixing with 2-p-toluidinylnaphthalene sulfonate (TNS) in liquid chromatography. The indirect detection is based on fluorescence enhancement due to the formation of an inclusion complex between TNS and CD's. β-CD gave larger signal intensity than α- and γ-CD. Different selectivities were observed for alkyl-bonded silica stationary phases with different chain length.
    Additional Material: 7 Ill.
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  • 189
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    Analysis of Methylcitric Acid by Enantioselective Multidimensional Gas Chromatography-Mass Spectrometry (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 604-608 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC-MS) ; methylcitric acid (MCA) ; inherited metabolic disease ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Methylcitric acid (2-hydroxybutane-1,2,3-tricarboxylic acid-MCA) is a structural analogue of citric acid, but due to an additional methyl group it is a chiral molecule with two stereogenic centers and thus four stereoisomers are conceivable. MCA occurs naturally as prominent metabolite in body fluids of patients with inherited metabolic diseases such as propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency. Therefore methylcitric acid is considered to be an important diagnostic marker for these diseases. MCA is most likely produced from accumulated propionyl-CoA in these diseases by the enzyme si-citrate synthase from the citric acid cycle; however, there are other enzymes known which could catalyze the same reaction with different stereoselectivity, such as re-citrate synthase or the more specific enzyme methylcitrate synthase, found in microorganisms. Almost all methods dealing with MCA in the literature are non-enantioselective. For that reason there is no information about occurrence of MCA enantiomers in healthy people, patients with propionic acidemia, methylmalonic aciduria, or holocarboxylase synthetase deficiency and about value of enantiomeric distribution for diagnosis and long-term treatment. The enantioselective analysis of MCA as corresponding trimethyl ester was achieved by enantioselective multidimensional gas chromatography coupled with mass spectrometry using heptakis-(2,3-di-O-methyl-6-O-tert-butyl-dimethylsilyl)-β-cyclodextrin as chiral stationary phase. The described method allows a reliable screening of MCA in complex matrices like urine without time consuming sample preparation and with mass selective detection. During this investigation urine samples from various patients and healthy controls were analyzed. As concluded, MCA is a good diagnostic marker and can be easily measured by the method presented. Only the two stereoisomers (2S,3R) and (2S,3S) were detectable in patients and healthy controls. The varying ratios of these stereoisomers cannot presently be correlated with the health status of patients, although there are some indications that this might be possible. However, the quantitative levels of MCA, determined as the ratio of MCA absolute peak area divided by 1,000 to the creatinine contents of urine samples in this investigation, showed a dependence on the state of health and MCA would thus also be a possible marker for long-term treatment. Such a substance is of major interest nowadays since there are different studies searching for such a long-term marker in propionic acidemia or methylmalonic aciduria.
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  • 190
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    Relative Recoveries of Hydrocarbons from Geological Samples Using High Temperature Supercritical Fluid Extraction: Contributions from Thermal Desorption (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 623-627 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; hydrocarbons ; high temperature ; thermal desorption ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The extraction of n-alkanes, polyaromatic hydrocarbons (naphthalene, methylated naphthalenes, phenanthrene, methylated phenanthrenes, anthracene, and methylated anthracenes) and biomarkers (hopanes) from Posidonia shale by high temperature supercritical fluid (HT-SFE) carbon dioxide extraction has been evaluated, including the relative contributions from thermal desorption and relative comparisons to conventional Soxhlet extraction. These current results confirm those of previous studies indicating a widely differing extractability of strongly and weakly associated hydrocarbons in ancient sediments and the significantly higher recoveries possible using HT-SFE compared to conventional Soxhlet extraction. The present study also demonstrates that these high HT-SFE recoveries are due to true extraction rather than simple thermal desorption and that this procedure is a useful tool to study speciation as well as total extractable hydrocarbons from sediments.
    Additional Material: 2 Ill.
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  • 191
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    Stereoisomeric Flavor Compounds LXXXII Dill Ether and Its Stereoisomers: Synthesis and Enantioselective Analysis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 631-634 
    Details
    ISSN: 0935-6304
    Keywords: Dill ether ; stereoselective synthesis ; dill ether stereoisomers ; enantioselective multidimensional gas chromatography-mass spectrometry (enantio-MDGC/MS) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 2 Ill.
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  • 192
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    Complete Separation of Isomeric Penta- and Hexachloronaphthalenes by Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 639-643 
    Details
    ISSN: 0935-6304
    Keywords: Cyclodextrin ; Halowax ; hexachloronaphthalene ; PCN ; polychlorinated naphthalenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 193
    Electronic Resource
    Electronic Resource
    Theory of Fast Capillary Gas Chromatography Part 4: Column Performance vs.Liquid Film Thickness (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 501-508 
    Details
    ISSN: 0935-6304
    Keywords: Fast GC ; film inefficiency factor ; high pressure drop ; thick film columns ; thin film columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The negative effect of the liquid stationary phase film thickness on the column efficiency is strongest for peaks with retention factors, k, in the vicinity of k = 0.3-0.4 and rapidly diminishes with the departure of k from that region. Additionally, at the high pressure drop required for fast analysis of complex mixtures, the negative effect of the same film thickness diminishes with the increase in column length, regardless of the k values. In practice, it is recommended to ignore the film thickness and optimize the columns as thin film ones regardless of their actual film thickness. Accounting for the film thickness results only in a modest improvement in the resolution for a few affected peaks - those with k = 0.3-0.4. However, this improvement comes at the cost of a substantial increase in analysis time, and should be used only as the action of the last resort.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 194
    Electronic Resource
    Electronic Resource
    Isolation and Characterization of Wax Esters in Fennel and Caraway Seed Oils by SPE-GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 514-520 
    Details
    ISSN: 0935-6304
    Keywords: Solid-phase extraction ; high temperature - gas chromatography ; gas chromatography - mass spectrometry ; wax esters fennel seed oil ; caraway seed oil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A rapid method for the isolation and quantitative determination of wax esters in vegetable oils was developed. For the first time wax esters in oils were separated from the triglyceride matrix by means of solid-phase extraction, which allows rapid sample preparation in parallel and therefore a high sample throughput. The thus obtained wax ester fractions of fennel and caraway seed oils were analyzed by high temperature gas chromatography. GC-MS analyses were carried out using electron impact ionization in order to characterize the wax ester fraction. With respect to the results of the GC-MS analyses different isomers of saturated wax esters with the same carbon number were observed. Additional monounsaturated wax esters with an unsaturated fatty acid moiety were identified.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 195
    Electronic Resource
    Electronic Resource
    Comparative Methodology for Isolation of Flavonoid Glycosides from Clusia criuva Cambess (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 527-530 
    Details
    ISSN: 0935-6304
    Keywords: Clusia criuva Cambess ; counter-current chromatography ; flavonoids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The family Guttiferae belongs to the superorder Theiflorae, order Theales and according to Dahlgren's system of classification, it is equivalent to Hypericaceae (=Clusiaceae) [1]. This family consists of 49 genera encompassing over 1000 species of wide distribution in the tropics as shrubs and trees [2]. Plants of the genus Clusia have been used in folk medicine for the treatment of different kind of illness such as: febrifuge, anti rheumatic, purgative, for stomach problems and, in Brazil, they are very commonly used to heal wounds [3]. The key of any study of material from natural sources is the availability of suitable separation methods for the isolation of pure products [4-6]. Tentatives for separations using chomatography on solid support phases were not very efficients in the fractionation of Clusia criuva Cambess methanolic/ethyl acetate extracts. However, the use of counter-current chromatography, an all liquid technique, showed advantages in comparison with the more traditional liquid-solid separation methods and even with HPLC. In this sense it was possible to isolate flavonoid glycosides from ethyl acetate extract of Clusia criuva, in a very short operation time.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 196
    Electronic Resource
    Electronic Resource
    Fast Solvating Gas Chromatography of Environmentally Important Compounds Using Polymer-Encapsulated Silica Particles (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 541-546 
    Details
    ISSN: 0935-6304
    Keywords: Solvating gas chromatography ; gas chromatography ; fast separation ; pesticides ; herbicides ; aldehydes ; packed capillary columns ; polymer-encapsulated silica ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Rapid separations of selected environmentally important polar compounds using polymer-encapsulated silica stationary phases and a carbon dioxide mobile phase under solvating gas chromatography (SGC) conditions are reported. Ten underivatized short chain aldehydes and ten nitrogen-containing herbicides were separated within 1 min and 5 min, respectively, using a 30 cm×250 μm i. d. column packed with diol-bonded, polyethylenimine (PEI)-coated, and hexamethyldisilazane (HMDS)-end-capped silica particles (5 μm, 120 Å). Seven organophosphorus pesticides were resolved in less than 5 min using a 30 cm×250 μm i. d. column packed with polymethylhydrosiloxane-deactivated and SE-54 encapsulated silica particles. Separation numbers per unit time increased with pressure and temperature ramps. Both rapid pressure and temperature programming can be used to increase the speed of SGC. The effects of pressure and temperature on apparent retention factors of solutes with various polarities were investigated using diol-PEI-HMDS silica particles in SGC.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 197
    Electronic Resource
    Electronic Resource
    Evaluation of Dead Time Calculation in Reversed-Phase Liquid Chromatography Using a Multiparametric Mathematical Method (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 559-564 
    Details
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; dead time ; multiparametric least-squares adjustment ; homologous series ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In reversed phase liquid chromatography (RP-HPLC), the validity of a multiparametric non-linear least-squares regression iterative method for the determination of the column dead time tM and the regression parameter (slope b), based on the use of alkan-2-ones, alkyl aryl ketones, and 1-nitroalkanes has been evaluated. The determination of tM and b has been extensively studied for two mobile phase systems acetonitrile-water and methanol-water on seven octadecyl-C18 and one octyl C8 analytical columns. The calculated tM and b values were compared with those obtained by Guardino's and Grobler's methods. The influence exerted thereon by the nature of the homologous series, the mobile phase composition, and the packing materials were investigated.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 198
    Electronic Resource
    Electronic Resource
    Supercritical Fluid Extraction (SFE) Optimization by Full-Factorial Design for the Determination of Irganox 1076, Irgafos 168, and Chimassorb 81 in Virgin and Recycled Polyolefins (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 553-558 
    Details
    ISSN: 0935-6304
    Keywords: SFE ; experimental design ; additives ; recycling ; polyolefins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The performance and feasibility of supercritical fluid extraction (SFE) applied to the extraction of some antioxidants (Irganox 1076, Irgafos 168) and one UV-stabilizer (Chimassorb 81) from both virgin and recycled low density polyethylene (LDPE), and virgin high density polyethylene (HDPE) are studied. Due to the high number of variables a full-factorial design has been applied to minimize the number of experiments required to reach the optimum extraction conditions. Further analysis has been carried out off-line by reversed-phase HPLC. Modification of the physical properties of the polymeric matrix and increased number of recycling cycles as well as the influence of physical properties on the efficiency of SFE are also discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 199
    Electronic Resource
    Electronic Resource
    Capillary Electrophoresis as an Efficient Tool in the Determination of Low Association Constants between Polyhydroxy Compound and Samarium Cation (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 595-598 
    Details
    ISSN: 0935-6304
    Keywords: Xylitol ; samarium ; weak association ; equilibrium constant ; capillary electrophoresis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---No abstract
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 200
    Electronic Resource
    Electronic Resource
    Effects of Blending Bare-Silica and Reversed-Phase on Retention of Neutral Compounds in Capillary Electrochromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 599-603 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography ; retention ; mixed stationary phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Most commercially available instruments for capillary electrochromatography (CEC) have a fixed configuration and lack the flexibility to use shorter columns. Applying a blended stationary phase (a phase consisting of a given ratio of bare silica and reversed phase material) can simulate columns of different length in CEC. The goal of this work was to examine the effect of the degree of blending of reversed-phase columns (with bare silica) on the speed of the separation of neutral compounds in CEC. Optimum column packing mixture was determined from the variation of the solute retention factors as a function of the ratios of blending of reversed-phase and bare silica. By adjusting the column composition, solute retention factors and the analysis run time were halved when compared to a pure reversed-phase column of the same length. Stationary phase blending can be considered as an additional parameter to mobile phase variation, column temperature and applied electric field for the optimization of selectivity and analysis time. By adjusting the stationary phase composition, mobile phase composition, column temperature and applied electric field, the analysis run time of neutral components was decreased more than 75% when compared to a separation obtained on neat reversed-phase column of the same dimensions. The linear dependence of the retention factors as a function of the blend ratio (reversed phase/bare silica) offers a framework for designing a “blended” packed capillary column for CEC separations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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