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  • Analytical Chemistry and Spectroscopy  (35)
  • Chemistry  (35)
  • On-line SFE-GC  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The magnitude and reproducibility of the electroosmotic flow in silica capillary tubes (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 325-334 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrophoresis ; Repeatability of electroosmotic flow ; Silica capillary tubes ; Column pretreatment ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of a number of factors, such as the nature of the buffer, the presence of additives therein, the manufacturing conditions, and the pretreatment of the capillary, on the magnitude and repeatability of the electroosmotic flow (EOF) in silica capillary tubes has been investigated. It was established that the nature of the buffer plays the most significant role in respect of the stability and magnitude of EOF, whereas the conditions used for manufacture and pretreatment of the tubing are less important. The EOF obtained using buffers consisting of tris(hydroxymethyl)aminomethane and ethylenediamine was more repeatable than that obtained using pure phosphate buffers. Buffer additives such as sodium dodecylsulfate, 1-butanol, sodium salts of 1-pentanesulfonic acid and 1-heptanesulfonic acid, altered the magnitude of the EOF only, not its repeatability.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240170509
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The Use of Non-Splitting Injection Techniques for Trace Analysis in Narrow-Bore Capillary Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 491-497 
    Details
    ISSN: 0935-6304
    Keywords: Fast GC ; narrow-bore columns ; trace analysis ; splitless injection ; on-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of hot splitless, cold splitless, and on-column injections for trace analysis in narrow-bore capillary GC is evaluated. Despite the low flow rates for the columns used, the required splitless times for splitless injections can be surprisingly short if liners with a small inside diameter are used. On-column injection can be applied by using an appropriate normal-bore precolumn coupled to the narrow-bore analytical column using a specially designed low dead volume column connector. The effects of the experimental conditions such as sample volume, injection temperature, and initial oven temperature on peak focusing and the discrimination and degradation behavior of the analytes are discussed. The possibilities to obtain sensitive and fast separations are illustrated by various applications.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Fast Capillary Gas Chromatography: Comparison of Different Approaches (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 583-586 
    Details
    ISSN: 0935-6304
    Keywords: Fast gas chromatography ; narrow-bore columns ; flash-2D-GC ; dedicated fast GC instrumentation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Savings in analysis time in capillary GC have always been an important issue for chromatographers since the introduction of capillary columns by Golay in 1958. In laboratories where gas chromatographic techniques are routinely applied as an analytical technique, every reduction of analysis time, without significant loss of resolution, can be translated into a higher sample throughput and hence reduce the laboratory operating costs. In this contribution, three different approaches for obtaining fast GC separations are investigated. First, a narrow-bore column is used under conventional GC operating conditions. Secondly, the same narrow-bore column is used under typical fast GC conditions. Here, a high oven temperature programming rate is used. The third approach uses a recent new development in GC instrumentation: Flash-2D-GC. Here the column is placed inside a metal tube, which is resistively heated. With this system, a temperature programming rate of 100°/s is possible. The results obtained with each of these three approaches are compared with results obtained on a column with conventional dimensions. This comparison takes retention times as well as plate numbers and resolution into consideration.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    HPLC-FID with Superheated Water as the Eluent: Improved Methods and Instrumentation (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 613-616 
    Details
    ISSN: 0935-6304
    Keywords: Micro LC ; FID detection ; superheated water ; alcohols ; aldehydes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In the current study, an HPLC-FID system using superheated water as the eluent is constructed and further improved. Signal stability during temperature programmed operation was improved by using separate thermostatting of the 50 μm capillary restrictor. Operating the restrictor at 75°C prevented the superheated water from sputtering in the restrictor. Conventional octadecyl-modified silica, thermostable polymeric reversed phase and carbon type HPLC columns were used. The feasibility of the system is demonstrated by the analysis of a variety of compounds such as alcohols and aldehydes. It is shown that increased temperatures decrease elution times and, in addition to this, frequently improve peak shapes and column efficiencies. The separation of lower aldehydes is performed at 175°C with a detection limit in the low μg/ml range. The possibility of temperature programming is demonstrated for the separation of a range of alcohols. Furthermore, it is shown that temperature programming can be used for sample enrichment. Large volume injection with low temperature enrichment resulted in good peak shapes and a significant improvement of the detection limit. In this way, detection limits of 0.2 μg/ml (ppm) could be obtained for the aldehydes studied. Finally, the possibilities of using mobile phase additives as, e.g., buffers were briefly examined.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Equilibrium-Sorptive Enrichment: A Novel Technique for Trace Analysis in Air (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 231-234 
    Details
    ISSN: 0935-6304
    Keywords: Trace analysis ; air samples ; BTX ; equilibrium-sorptive enrichment ; 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)
  • 6
    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.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    Development and evaluation of an interface for coupled capillary supercritical fluid chromatography/magnetic sector mass spectrometry. Application to thermally unstable and high molecular mass compounds (1996)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 17-22 
    Details
    ISSN: 0935-6304
    Keywords: Capillary Supercritical Fluid Chromatography ; Mass Spectrometry ; SFC-MS ; On-line combination ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An interface for coupling supercritical fluid chromatography to a magnetic sector mass spectrometer was developed and evaluated. The interface is based on direct introduction of the mobile phase, carbon dioxide, into the ion-source of the mass spectrometer. The SFC-MS system was optimized with respect to the signal-to-noise ratio. Under optimized conditions, the estimated detection limit for n-pentadecane is approximately 30 ppm. Spectra obtained in the electron-impact ionization mode show a very good similarity with library spectra. The performance of the SFC-MS system was evaluated by the analysis of a number of test mixtures. A sample containing several low molecular mass, thermally unstable compounds, which could neither be analyzed by GC-MS nor by LC-MS, was analyzed. Also for the analysis of high molecular mass compounds, the coupled system showed a good performance.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240190103
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of sulfur components in natural gas: A review (1994)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 17 (1994), S. 373-389 
    Details
    ISSN: 0935-6304
    Keywords: GC ; Natural gas analysis ; Sulfur components ; Selective enrighment ; Sulfur selective detection ; Calibration ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: More stringent environmental regulations as well as higher demands presently being imposed on the sulfur content of natural gas feed-stocks for chemical processes necessitate the development of new analytical procedures for sulfur determination in natural gas. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. The complexity of the natural gas matrix as well as the extremely low concentration levels at which the sulfur species occur make the development of these analytical methods a true challenge. In this review the three steps common for analytical methods for trace analysis in complex matrices, i.e. pretreatment, chromatographic separation, and detection, are discussed in detail. Possible methods for calibration of the system are discussed in the final section.Various techniques to determine sulfur in natural gas are described. Depending on the application, the most suitable system has to be selected. For example, for on-line application in a hazardous area a simple and rugged system is required, i.e. a simple gas chromatograph with a flame photometric detector, while for laboratory application a more complex instrument including preconcentration, column switching, and more exotic detection systems could be more suitable. Therefore it is crucial to define the requirements of the instrument at an early stage and use the information in this review article to develop/select a dedicated instrument/procedure for the problem at hand.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240170603
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Pressure drop effects on selectivity and resolution in packed column supercritical fluid chromatography (1996)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 449-456 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography (SFC) ; Packed columns ; Pressure drop ; Selectivity ; Resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of pressure drop on retention, selectivity, plate height and resolution was investigated systematically in packed supercritical fluid chromatography (SFC) using pure carbon dioxide as the mobile phase. Numerical methods developed previously which enabled the prediction of pressure gradients, diffusivities, capacity factors, plate heights and resolutions along the length of the column were used for the model calculations. The effects of inlet pressure and supercritical fluid flow rate on selectivity and resolution are studied. In packed column SFC with pure carbon dioxide as the mobile phase, the pressure drop can have a significant effect on resolution. The flow rate is shown to have a larger effect than generally realized. The calculated data are shown to be in good agreement with the experimental results. Finally, the variation of the chromatographic parameters along a 5.5 meter long model SFC column is illustrated. The possibilities and limitations of using long packed columns in SFC are discussed. It is demonstrated that long columns with large plate numbers do not necessarily yield better separations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240190806
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  • 10
    Electronic Resource
    Electronic Resource
    Environmental applications of large volume injection in capillary GC using PTV injectors (1996)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 69-79 
    Details
    ISSN: 0935-6304
    Keywords: Large volume injection ; PTV injector ; Water analysis ; River sediment ; Pesticides ; Polycyclic aromatic hydrocarbons (PAHs) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Temperature programmable (PTV) injectors with packed widebore (ca. 3.5 mm i.d.) liners are used for large volume injection in capillary gas chromatography with the aim to simplify and/or improve off-line sample pretreatment proecdures. A simple procedure for optimization of large volume PTV injection is described. The system performance, i.e. linearity and repeatability, is evaluated for polar nitrogen/phosphorus containing pesticides (PTV-GC-NPD) and organochlorine pesticides (PTV-GC-ECD) in river water extracts as well as for polycyclic aromatic hydrocarbons (PAHs) in river sediment (PTV-GC-MS).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240190203
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