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  • 1990-1994  (54)
  • 1980-1984
  • 1975-1979
  • 1993  (54)
  • Gas chromatography
  • Nuclear reactions
  • Physics
  • 1
    ISSN: 1432-2285
    Keywords: Abies alba ; Abscisic acid ; Damage ; Gas chromatography ; Needles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The amount of abscisic acid (ABA) in needles of silver fir from a natural location was investigated with regard to position in the crown, damage, seasonal variation, and needle age. Because of problems of quantification of ABA in coniferous needles, which contain numerous secondary plant products, a method for reliable determination of both isomers cis-trans-ABA (c-ABA) and transtrans-ABA (t-ABA) was developed. By means of gas chromatography (GC) using an electron capture detector (BCD) and a programmed temperature vaporizer (PTV) injector complete separation of both compounds was achieved. Two different pairs of fir were investigated — in each case a damaged and a healthy tree. Needles from both trees from the first and the second pair collected in September contained 500–1100 ng c-ABA/g fresh weight (FW), and the concentrations of t-ABA varied from 400 to 700 ng/g FW. Investigations from the second pair show highest amounts of 2900 ng/g Fw c-ABA and 1800 ng/g FW of t-ABA in May and June. For the first pair a higher c-ABA content was found in needles from the top of the crown than in those from the middle and the base. This difference could not be confirmed in the analysis of the second pair. Because of the strong natural deviation no statistically significant difference between the healthy and the damaged tree was found. The first pair of firs examined showed a higher t-ABA concentration than the second one. In this case the highest amount was found in the top of the crown. Methodical mistakes during the clean-up procedure and in quantification by gas chromatography could be excluded. The presence of c- and t-ABA in the purified extract was corroborated by mass spectrometry. With regard to the seasonal variation both isomers of ABA show an unequivocal trend. The maximum concentration is achieved in May to June, whereas the content is minimal in August/September. In any case the level of t-ABA is lower than that of c-ABA. No correlation between the amount of ABA and the needle age could be established.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International archives of occupational and environmental health 64 (1993), S. 503-507 
    ISSN: 1432-1246
    Keywords: Biological monitoring ; Carbon disulphide ; Dithiocarbamate ; Gas chromatography ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Blood carbon disulphide (CS2), both free and total, was determined by gas chromatography-mass spectrometry in 112 “normal” subjects and in 20 subjects employed in a dithiocarbamate factory, comprising ten blue-collar workers involved in dithiocarbamate production and ten white-collar office staff. The ten production workers were examined over two workshifts, the first at the beginning of the week (Monday) and the second after an intervening period of at least 1 day. Three blood samples were taken for each shift studied, one prior to starting work, one at the end of the shift and the third 16 h after the end of the shift (on the following morning). The mean CS2 blood levels measured in the 112 normal subjects was 663 ng/l for the free fraction and 3178 ng/l for the total. In 16 blood samples taken from the ten dithiocarbamate factory office workers, the mean free and total CS2 blood levels were 846 and 4140 ng/l, respectively, i.e. not significantly different from those observed in the normal subjects. At the end of the first 8-h shift, the ten dithiocarbamate factory production workers had free and total CS2 values of 1070 and 8471 ng/l, respectively, which were significantly higher than those observed prior to starting work (240 and 4738 ng/l). All the total CS2 levels measured in the shop-floor workers, with the sole exception of the values recorded prior to the start of the Monday shift (4738 ng/l), ranged from 7047 to 8471 ng/l and were significantly higher than those measured in the white-collar staff (4140 ng/l).
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  • 3
    ISSN: 1432-1246
    Keywords: Acrylonitrile ; Adducts ; Biological monitoring ; Gas chromatography ; Hemoglobin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new, simple and fast procedure of measuring acrylonitrile (ACN) in ACN derived mercapturic acids such as S-(2-cyanoethyl)-L-cysteine(CyEC), and in hemoglobin (Hb) and plasma protein adducts and urinary metabolites in rats and humans exposed to ACN was developed. ACN in mercapturic acids or proteins was analyzed by capillary gas chromatography (GC) by liberating ACN at a high-temperature in the injector port of GC with or without oxidizing sulfur atoms of the ACN-bound cysteines into sulfoxide form by hydrogen peroxide in vitro. At 350 °C, more than 90% of ACN in authentic CyEC was recovered by this method. Increasing a single ip dose of ACN from 5 to 50 mg/kg produced proportional increases in ACN bound to Hb 24 hr after the treatment. The alkylation of plasma protein with ACN was about 1/10 as low as that of Hb. After repeated daily ip doses of 1–10 mg/kg, ACN in Hb decreased with a half-life of about 9 days. ACN was also detected in the blood of workers exposed to ACN for 1 to 10 years at a Siberian synthetic rubber factory.
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  • 4
    ISSN: 1432-0738
    Keywords: Pigment Yellow 17 ; 3,3′-Dichlorobenzidine ; Biotransformation ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were exposed by inhalation to the technically highest administrable concentration of 230 mg Pigment Yellow 17/m3 air for 4 h. Inhalability of the dust was guaranteed by a mass-median aerodynamic diameter of 1.0–1.1 μm. For 14 days after exposure, urine and serum samples were analysed for 3,3′-dichlorobenzidine, the parent carcinogenic amine of the test compound. No 3,3′-dichlorobenzidine could be detected either in urine or blood, the detection limit being 5 ng/ml for both media. Based on the results of this study there is no evidence for metabolic cleavage of Pigment Yellow 17 to 3,3′-dichlorobenzidine in the rat.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 35 (1993), S. 649-652 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Triglycerides in cheese ; Programme temperature (PTV) injection ; Silica capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid gas chromatographic method for the analysis of triglycerides in cheese on a capillary column with a programmed temperature vaporizer has been developed. Fat were extracted with hexane to dryness. The reproducibility of the method was assessed and the coefficient of variation for the total triglycerides was 2.50%. Recovery of individual triglycerides ranged between 87 to 105%.
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  • 6
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Curie-point pyrolysis ; Multivariate analysis ; Sodium dodecylbenzene sulfonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Multivariate analysis can be applied to quantitative analysis of sodium dodecylbenzene sulfonate (DBS) by pyrolysis gas chromatography. The pyrograms obtained from mixtures of DBS and polyoxyethylene lauryl ether (PEG) were normalized for the peak heights and areas of several internal standards which appeared in every pyrogram, against the characteristics peaks for DBS and PEG. This normalization method gave smaller experimental errors than when using one internal standard. The normalization values were used for cluster analysis unchanged. The values were calculated correlation coefficients and principal component analysis was performed using 11 data base and a set of sample data simultaneously. One calibration curve was calculated from the principal component scores. The DBS content of a sample was obtained from the calibration curve. Calculated values were in fair agreement with theoretical values.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 36 (1993), S. 187-190 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid-phase extraction disks ; Pesticides ; Soil analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A systematic study comparing the methodology and analytical results obtained in an investigation of seven pesticide residues (Molinate, Atrazine, Carbofuran, Pirimicarb, Prometryn, Malathion and Tetrachlorvinphos) in soil samples is reported. Solid-phase extraction (SPE) using glass columns and 47 mm disks of octyl and octadecyl-bonded silica was used in the pesticide analysis. The best extraction efficiency and clearest extracts are obtained with C8 disks. The analyses were carried out by capillary gas chromatography with nitrogen and phosphorus detection. Recovery experiments were performed at ppb levels in spiked soil samples. The average recoveries of the compounds were 53–77%. Detection limits are between 5 and 30 ng g−1 based on 5 g moist soil sample. The method was validated by comparing it with conventional liquid-liquid extraction.
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  • 8
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fatty acid methyl esters ; Diesel fuel substitute ; Glycerol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A GC method for the determination of free glycerol in vegetable oil methyl esters used as diesel fuel is described. The sample preparation includes dissolving in dimethylformamide, silylation with bistrimethylsilyltrifluoroacetamide (BSTFA) and separation on a methyl silicone capillary column using either FID or MS detection. The recovery was tested using standard samples containing known amounts of glycerol. The results of the analysis of different samples were compared with those obtained by enzymatic determination. The method described offers a far more sensitive and quick determination of free glycerol compared to other methods.
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  • 9
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Electron capture detection ; Trichothecenes ; Cereal grain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various analytical methods developed for trichothecene determination, including TLC, HPLC, GC, supercritical fluid chromatography (SFC) and enzyme immuno assay (EIA) are reviewed. In addition a new method is described for the simultaneous determination of the trichothecene mycotoxins deoxynivalenol (DON), nivalenol (NIV), 3-acetyldeoxynivalenol (3-ADON), diacetoxyscirpenol (DAS), T-2 toxin (T-2), HT-2 toxin (HT-2) and T-2 triol (TRIOL), in Austrian wheat and corn samples by GC-ECD. A clean-up procedure has been developed using a combination of liquid-liquid and liquid-solid extraction. Trichothecenes were detected as their heptafluorobuturyl esters or alternatively as trimethylsilyl ethers (only sensitive for deoxynivalenol and nivalenol) using nandrolone or chloramphenicol as internal standard. Four derivatization techniques using HFBI, HFBA+DMAP on polystyrene, TMSI and TMSI+BSA+TMCS have been studied and the advantages and disadvantages of each are discussed. Quantification of trichothecenes from 10 to 1000 ppb in cereals could be accomplished routinely.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 215-217 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Unified retention indices ; Dimethylsiloxane stationary phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic, unified retention-indices of 56 alkylbenzenes up to C15 on dimethylsiloxane OV-101 and SE-30 stationary phases are given. These values agree well with the corresponding experimental values used in the statistical treatment of the experimental data.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 259-263 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Quantitative analysis ; Ethylene oligomer by-products ; n-Alkanes, n-alkenes and 2-alkyl-1-alkenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method using temperature-programmed poly-dimethylsiloxane OV-101 and poly(pheny ether) (5 rings) capillary columns was developed to separate and quantify the reaction by-products in ethylene oligomers. It was found that the content of 2-alkyl-1-alkenes, 2-alkenes and n-alkanes in the C8−C18 α-olefin fractions amounts to 29, 10 and 2.6% respectively.
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  • 12
    Electronic Resource
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    Springer
    Chromatographia 37 (1993), S. 211-214 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Organic solvents ; Routine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method for the analysis of organic solvents in chemical products is described. The analysis is performed by the use of a polar column, Supelcowax 10, and a non-polar column CP-Sil-5CB. Samples containing a non-volatile matrix or water were analysed by headspace analysis. The identification of the solvents in a sample, based on GC retention times on one column, is confirmed by GC of the sample on the second column. The method has been found to be suitable for the routine analysis of solvent mixtures.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 264-270 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Temperature programmed ; Peak widths ; Polynomial interpolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isothermal chromatographic measurements lead directly to ΔH v o and A (entropy term) of solutes, and three constants of an empirical relationship between peak width and column temperature. From the thermodynamic parameters ΔH v o and A retention temperatures have been computed by means of a theoretical model including temperature dependence of carrier gas viscosity, and subsequently retention times; programmed retention indices have been determined by linear and polynomial interpolations. By substituting the value of the calculated retention temperature in the above-mentioned relationship, peak width at half-height for a linear temperature may be estimated. Predicted retentions correlate with observed data, with a P-value ≤0.01; simulation accuracy is generally 6–10% for peak widths. Retention indices of some organochlorine species, separated on an OV-101 capillary column, may differ by as much as 26 units depending on the method of calculation. Polynomial-calculated indices are more consistent with the retention index scheme, and have smaller standard deviations and better constancy at different heating rates.
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  • 14
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Inverse gas chromatography ; Poly(ethylene glycol) 20M ; Retention mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The properties of poly(ethylene glycol) 20M (PEG 20M) coated on the hydroxylated surface of Chromaton N AW were investigated by inverse gas chromatography. It was found that the solid form of PEG 20M exhibits partition as the retention mechanism even below its melting range. The contribution of adsorption to the specific retention volume was also determined. It was demonstrated that inverse gas chromatography establishes the existence of a polymer surface layer but precise determination of its thickness is difficult. The limitation of the applicability of inverse gas chromatography results from the structure of the investigated surface layer which is thin and not coherent so that solute molecules can penetrate it.
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  • 15
    Electronic Resource
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    Springer
    Chromatographia 35 (1993), S. 33-37 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Crown ether polysiloxane phases ; Selectivity mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The phase recognition mechanism of nine groups of position isomers on four crown ether polysiloxanes, OV-1701 and PEG 20M has been investigsated by measuring various thermodynamic parameters. The high selectivity of crown ether polysiloxane phases is due to hydrogen bonding and the extent of fitting between the analytes and the crown ethe cavity. The effects on selectivity of cavity size, heteroatoms and substituent groups on the crown ether are discussed.
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  • 16
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Equilibrium headspace sampling ; Partition coefficient determination ; Theory of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The new phase ratio variation method is described which represents a convenient way for the determination of gas-liquid partition coefficients for practical purposes, utilizing equilibrium headspace-gas chromatography (EHS-GC). This method is based on the relationship between reciprocal peak area and the phase ratio in the vial containing the sample solution; it involves regression analysis of the EHS-GC measurements of a number of sample vials containing the same sample solution but with a wide variation of phase ratios. Examples are given for both aqueous systems and systems consisting of a stationary (liquid) phase used as the solvent; comparison of the measured values with results obtained by other methods shows satisfactory agreement. A critical discussion of the conditions influencing the accuracy of the analytical results is given.
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  • 17
    Electronic Resource
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    Chromatographia 35 (1993), S. 109-110 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Unified retention index ; Correlation of data ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic unified retention indices for 43 hydrocarbons (alkanes and cycloalkanes) are given for squalane and OV-101. Comparison of these values and unified retention index increments are presented as linear regression equations with high correlation coefficients and acceptable standard deviations.
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  • 18
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    Chromatographia 35 (1993), S. 160-166 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Neural networks ; Classification ; Pattern recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Artificial Neural Networks are proposed for the classification of vegetable oils submitted to gas chromatography analysis through their FAME profiles. Three important neural networks are evaluated here: the Hopfield model as a content-addressable memory (CAM), the Hamming model and the multi-layer perceptron. A brief description of these nets is first presented and further implemented for the classification of known vegetable oils. After the learning step, unknown samples are presented to the nets and the identification step performed. The performances of these nets are compared for the recognition of popular vegetable oils, including several edible oils.
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  • 19
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Mass spectrometry ; Atomic emission spectroscopy ; Pulp mill effluents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three chlorinated dimethyl sulfones and five chlorinated thiophenes have been identified in the alkaline extraction liquor from a bleach plant by gas chromatography with atomic emission detection (GC-AED) and with mass spectrometry (GC-MS). The information on elemental content obtained by GC-AED enabled a rapid screening of the sulfur compounds and provided important structural information complementary to the mass spectral data. Quantitation was accomplished by GC-AED based on universal calibration.
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  • 20
    Electronic Resource
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    Springer
    Chromatographia 35 (1993), S. 209-215 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Gas chromatography-mass spectrometry ; Tagetes ; Plant volatiles ; Extractions ; Natural insecticides ; Mosquitos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Volatiles from three species of the genustagetes, commonly called marigold have been isolated and characterized. Simultaneous steam distillation extractions (SSDE) produced consistently extracts of higher insecticidal activity than Soxhlet extractions. Methylene chloride was the best solvent. Volatiles isolated from theminutae species showed higher activity than those frompatula anderecta. Comparison of extracts from the flower, foliage and roots of the plant showed that most of the activity is located in the flower. The volatiles are highly effective toward both larvae and adult mosquitoes.
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  • 21
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    Chromatographia 35 (1993), S. 237-240 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Enantioselectivity ; Polysaccharide chiral stationary phase ; Amylose tris(n-butylcarbamate) ; Grob test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Seven aromatic and alkyl amylose and cellulose carbamates have been tested as chiral stationary phases in gas chromatography. One of them, amylose tris(n-butylcarbamate) can be used for enantiomer separation.
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  • 22
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    Springer
    Chromatographia 35 (1993), S. 290-294 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Solid phase extraction ; Organochloride pesticides ; Water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography of chlorinated pesticides in water is carried out after adsorption of a 50 mL sample using a cartridge containing 100 mg CN-bonded porous silica and extraction with 500 μL pentane. The average recovery for eight organochloride pesticides at 1 ppb was 〉95%. The procedure described is simple, selective and reproducible.
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  • 23
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    Springer
    Chromatographia 35 (1993), S. 339-343 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Preconcentration techniques ; Trace gas analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The blanks in preconcentration methods for determining trace amounts of impurities in ultra-pure gases, which include the preconcentration volume of sample gases, carrier gas impurities and atmospheric contamination are discussed and three concentration methods for eliminating blank errors are proposed. These are, the differential volume method by concentrating at the same flow-rate but different times (DVMSF), the differential time method by concentrating the same volumes at different flow-rates (DTMSV) and the differential volume method by concentrating for the same times but different flow-rates (DVMST). DVMST is proposed as the best method for its ability to eliminate all blank errors described. The methods are used to determine trace amounts of Ar+O2 and N2 in ultra-pure hydrogen. Calculations demonstrate that the methods can effectively improve analytical accuracy.
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  • 24
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Micropacked columns ; Retention behavior ; LC silica packing materials ; Silanol groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic retention of cyclohexane and benzene on microcolumns packed with silica-based materials for liquid chromatography has been investigated to elucidate the relationship with the surface properties of the packing materials. Differences in capacity factors (Δk′) for these two hydrocarbons were related to the surface area of the packing materials. For untreated silica gels, the Δk′ value increased with increasing total surface area of the column employed and measurement of Δk′ for chemically-bonded stationary phases allowed estimation of accessible residual silanol groups.
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  • 25
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pesticides in groundwater ; Solvent extraction ; Multiresidue analysis ; Selective detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple multi-residue procedure has been developed and applied to the analysis of pesticides in groundwater samples from the Comunidad Valenciana, a predominantly agricultural area on the Mediterranean coast of Spain. The procedure includes a liquid-liquid extraction, after addition of NaCl on the samples, and a subsequent analysis by capillary gas chromatography using a dual detection system with electron capture and nitrogen-phosphorous detectors. This allows the determination of more than 30 compounds (organophosphorous, organochlorine and pyrethroid pesticides) at the low ppb (μg l−1) levels. Detection limits obtained varied between 0.01 μg l−1 (lindane, fonofos) and 0.5 μg l−1 (cypermethrin). An additional injection of the sample extracts into a gas chromatograph equipped with a column of different polarity and electron capture detector is used for the confirmation of chromatographic peaks. The recommended procedure has been applied to 66 ground water samples. Pesticides, including organophosphorus and organochlorine compounds were detected in 31 of them, in levels ranging from 0.02 to 0.7 μg l−1.
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  • 26
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; PTV-System ; Ethephon in drinking water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An indirect GC method is described for the determination of Ethephon in drinking water on the basis of the headspace analysis of the ethylene formed from Ethephon. In order to reach the necessary detection limit, the entire volume of the static headspace distribution is transferred into a cold injection system (CIS). There, the ethylene is adsorbed on Carbosieve SIII at 10°C and, subsequently, desorbed at 300 °C. The water vapour included in the headspace is completely eliminated through the splitting system. By means of this technique, a detection limit of 0.05 μg/l water was reached.
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  • 27
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    Chromatographia 37 (1993), S. 399-401 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Viscosity ; Carrier gases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equations are derived for viscosities of H2, He, N2 and Ar for use at chromatographic temperatures which are accurate to within 0.3% for H2, and 0.1% for the other gases. The effect of pressure is usually negligible but may increase the viscosity of N2 or Ar by as much as 0.5% at 25°C or lower and 5 atm or higher.
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  • 28
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    Pharmacy world & science 15 (1993), S. 105-115 
    ISSN: 1573-739X
    Keywords: Calcium phosphates ; Drug compounding ; Excipients ; Particle size ; Physics ; Powders ; Tablets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ten commercially available calcium phosphates used for direct tableting were evaluated. The particle size distributions, powder properties, Sorption isotherms and pH values of aqueous slurries were compared. All samples showed good or at least sufficient flowability. Scanning electron micrographs illustrated the different kinds of manufacturing and gave hints on their expectable behaviour under compaction pressure. The sorption isotherms of identical chemical substances, which had been manufactured by different methods, differed strongly. This can be related to their specific surface areas. Most of the hydroxylapatites have large surface areas and can absorb up to more than 15% water at 93% relative humidity. Dibasic calcium phosphate dihydrate was non-hygroscopic and absorbed less than 1% water. With the exception of monobasic calcium phosphate monohydrate all calcium phosphates behaved quite neutral in water. Monobasic calcium phosphate monohydrate can be regarded as a solid acid. Although the calcium phosphates are usually stable substances, the role of crystal water in the case of dibasic calcium phosphate dihydrate and monobasic calcium phosphate monohydrate is problematic due to possible interactions with active ingredients.
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  • 29
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    Chromatographia 35 (1993), S. 503-505 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Silanol terminated Chirasil-Val ; Cross-linking with polyfunctional silanes ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the immobilization of Chirasil-Val has been studied based on the cross-linking which takes place between terminal silanols of Chirasil-Val and polyfunctional silanes. A leached, dehydrated and tetramethoxysilane-treated glass capillary coated with silanol terminated Chirasil-Val containing 5% tetraacetoxysilane as a cross-linking agent showed a maximum extractability of 15% without any loss of chirality.
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  • 30
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    Chromatographia 37 (1993), S. 51-56 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Halogenated hydrocarbons ; Headspace sampling ; ECD detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Simple sampling and preconcentration technique for the analysis of volatile halogenated hydrocarbons in water is described. For the separation a selective capillary column is used in combination with an ECD. Quantitative data are given.
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  • 31
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Fused silica open tubular columns ; Serial coupled columns ; Phase ratio optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary There are a number of parameters which have to be chosen depending on the analysis being done in gas chromatography. While the choice of stationary phase material is based on the solutes to be separated, the thickness is dependent on the concentration and the volatility of the components to be analyzed. This study undertakes a coupled column phase ratio optimization by connecting a short piece of a particular column prior to a normal length of an analytical column. Various columns of different dimensions (phase ratio), but of the same stationary phase material (methyl silicone), are coupled together by a deactivated glass press-fit connector, and the efficiency and capacity are measured. The coupling of fused silica open tubular columns is optimized in efficiency by matching or decreasing the phase ratio of successive columns. Capacity optimization is accomplished by increasing the phase ratio of consecutive columns. Capacity and efficiency optimization are opposing each other; therefore, if some efficiency can be sacrificed a substantial increase in capacity is possible.
    Type of Medium: Electronic Resource
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  • 32
    ISSN: 1612-1112
    Keywords: Supercritical fluid chromatography ; Gas chromatography ; High speed analysis ; Thermal desorption ; Two dimensional analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two-dimensional supercritical fluid-gas chromatography system was constructed and evaluated. A 50-μm i.d. capillary column coated with a 50 % cyanopropyl polysilixane stationary phase was used as the firstdimensional column. Group-type separations of polycyclic aromatic hydrocarbons, based on the number of aromatic rings, were achieved using this column under SFC conditions. A 25-μm i.d. liquid crystal column was used as the second-dimensional column under GC conditions. The effluent from the first column (SFC) was received continuously by the second column (GC) through a thermal desorption modulator. The thermal desorption modulator (prepared at the head of the second column) generated a series of concentration pulses from the first column effluent. These concentration pulses served as injections to the second column, and were developed into a corresponding series of high-speed chromatograms. Grouptype sample bands from the first column were separated into individual components on the second column. All sample substances passed through both columns to generate two sets of retention data, which could be used for more accurate compound identification.
    Type of Medium: Electronic Resource
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  • 33
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Capillary column sampling ; Additivity of variance in GC ; Aqueous samples ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The possibility of using capillary columns for both sampling and gas chromatographic analysis of aqueous micropollutants has been studied. Factors influencing gas chromatographic band dispersion of the solute were investigated and a mathematical relationship developed correlating the properties (ID, df) of the capillary columns to the degree of dispersion of adsorbed substances has been derived. The experimental results obtained with aqueous samples are in good agreement with the theoretically forecast data. The method developed allows gas chromatographic dosing of traces of organic substances, reducing inconvenience deriving from excessive sample handling to a minimum. Non-refocusing of the analyte does not, in any significant way, compromise column efficiency for substances that are not very soluble in water.
    Type of Medium: Electronic Resource
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  • 34
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace analysis ; Steam distillation ; Phenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-temperature headspace analysis performed under static conditions above 100°C increases the sensitivity of gas chromatographic determination of volatile phenols in aqueous solutions 20–100 fold and reduces the detection threshold, to 10 μg×1−1. To improve the sensitivity and reduce the threshold still further, preliminary concentration by high-temperature microdistillation at elevated pressure is proposed. A theoretical model of this process has been developed. The possibility of concentrating volatiles by high-temperature microdistillation has been experimentally confirmed.
    Type of Medium: Electronic Resource
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  • 35
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 36 (1993), S. 215-217 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Polar columns ; Vegetable oils ; Sterols ; Unsaponifiable matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The analysis of both the total unsaponifiable matter and the sterol fractions in vegetable oils has been performed with a new polar column (TAP, Chrompack). The use of a polar column, which is characterized by high thermal stability, has led to the identification of a greater number of constituents than the use of a nonpolar column (i.e. SE 52, SE 54). The polar column enhances the separation of the main classes of unsaponifiable matter (sterols, 4-methyl sterols and 4,4′-dimethyl sterols). When used for the unsaponifiable and sterol fraction analyses, it offers a powerful tool for characterizing the lipid source.
    Type of Medium: Electronic Resource
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  • 36
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid chromatography ; Mass spectrometry ; β-agonists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Different chromatography — mass spectrometry techniques for the analysis of β-agonists have been compared. Gas chromatography — mass spectrometry (electron impact) has been used, as also has liquid chromatography coupled to the mass spectrometer by either thermospray or electrospray interfaces. The results obtained by the three method were compared in terms of sensitivity, selectivity, and richness of information provided by the analysis. It was found that using electrospray ionization, very powerful analysis could be achieved with high sensitivity, thus providing significant potential for the analysis of β-agonists.
    Type of Medium: Electronic Resource
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  • 37
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Crown ether polysiloxane phases ; Capillary columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two crown ethers, di(tert-butylbenzo)-propyl-15-crown-5 polysiloxane (PSO-DTB-15C5) and dibenzo-propyl-15-crown-5 polysiloxane (PSO-DB-15C5) have been synthesized and coated onto fused-silica capillary columns. The chromatographic characteristics, including column efficiency, polarity, phase transition temperature, operating temperature range and selectivity, were studied. Excellent selectivity was obtained for the separation of polar position isomers, especially phenol and dinitrotoluene isomers. The separation mechanism is discussed.
    Type of Medium: Electronic Resource
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  • 38
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention indices ; Adsorption effects ; n-Tetradecenes ; n-Tetradecynes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The correction of the reproducibility of retention indices on polar capillary columns with different film thickness, using more polar reference standards instead ofn-alkanes, was investigated. It was found that the replacement ofn-alkanes by 1-alkenes, 3-alkynes and n-alkylbenzenes as standards significantly improves the reproducibility of retention indices and diminishes their temperature increments forn-alkanes,n-alkynes and arenes on PEG 20M columns.
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  • 39
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 35 (1993), S. 539-542 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid crystals ; Diffusion coefficients ; Xylenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The molecular diffusion coefficients of xylene isomers have been determined at different temperatures in the three phases (smectic, nematic and isotropic) of 4,4′-bis(heptyloxy)azoxybenzene (BHOAB) by gas chromatography. The results obtained are discussed in terms of molar volume, polarity and length-to-breadth ratio of several isomers. The activation energy of diffusion processes of solutes in the three phases of the liquid crystal has been calculated.
    Type of Medium: Electronic Resource
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  • 40
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 36 (1993), S. 225-233 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Selective ionization detectors ; Organic fuelled flames ; Lead, tin, phosphorus, halogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The selectivities of two flame-based ionization detectors identified as a Remote FID (RFID) and a Flame Thermionic Ionization Detector (FTID) have been improved by introducing methane as a fuel for the flame. Both the RFID and FTID feature a detector struture in which the ionization polarizer and collector are located several centimeters downstream of an oxygen-rich flame, rather than immediately adjacent to the flame as in a flame ionization detector. The RFID detects long-lived negative ions produced in the flame by the combustion of lead, tin, phosphorus, or silicon compounds. The FTID re-ionizes and detects neutral electronegative products generated by combustion of nitrogen, halogen, or phosphorus compounds. An organic-fuelled RFID can detect 1 pg Pb (Sn, P)/sec with a selectivity of the order of 106 versus hydrocarbons. An organic fuelled FTID is applicable to detection of compounds at nanogram and higher levels. FTID selectivity for PCB compounds in a transformer oil matrix is of the order of 105∶1. The improved selectivity achieved by using an organic-fuelled flame is also applicable to the detection of phospholipid and other non-volatile N, P, or Cl compounds using an FID/FTID detector accessory for a TLC/FID analyser.
    Type of Medium: Electronic Resource
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  • 41
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 105-106 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Occupational hygiene analysis ; Epichlorohydrin in air ; Trace analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method has been developed for the determination of trace amounts of epichlorohydrin in workplace atmospheres. Collection is peroormed in two bubblers in series both containing dichloromethane. Optimum conditions for sampling and analysis have been established. The lower limit of determination is 0.05 μg/mL with an RSD of ±5%.
    Type of Medium: Electronic Resource
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  • 42
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 277-280 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Hydrogenation of 1,5,9-cyclododecatriene ; Retention index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of the products obtained by the hydrogenation of 1,5,9-cyclododecatriene stereoisomers on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices of cyclododecatrienes, cyclododecadienes, cyclododecenes and cyclododecane were determined at three temperatures. The respective standard deviations were 0.3 and 0.6 i.u. The influence of the polarity of the stationary phases on the chromatographic retention of these cyclic hydrocarbones is discussed.
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  • 43
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 250-258 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Retention data ; Stationary phases ; Phase constants ; Linear free energy relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Specific retention volumes and retention indices for selected compounds can be predicted from different sets of stationary phase constants by multiple regression. Errors in the corresponding calculated retention times are between 5 and 15%. Intercept (A) and slope (B) values are given for 72 McReynolds stationary phases. The A value can be predicted from the retention index of benzene with a standard deviation of 9%.
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  • 44
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 37 (1993), S. 546-548 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Methyl methacrylate monomer ; Contact lens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified gas chromatographic method is described for the determination of free monomer in contact lenses, irrespective of the method of production. It thus becomes possible to assess very quickly the conformity of such lenses with hygiene regulations. This method allows direct supervision of production or determination of the quality of a product of unknown origin in only 15 min. Production tests of new polymerization initiators, reactors for polymerization, etc. can also be carried out.
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  • 45
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 188-191 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Thermostable WCOT columns ; PLOT columns ; Stainless steel ; Silicon layer for deactivation ; Simulated distillation ; PNA analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A layer of elemental silicon has been deposited on the surface of stainless steel tubing by means of chemical vapor deposition (CVD). Two kinds of capillary column were prepared from the deactivated tubing: cross-linked, silanol-terminated polydime-thylsiloxane wall coated open tubular (WCOT) columns and molecular sieve 13X porous layer open tubular (PLOT) columns. Unlike fused silica capillary columns, stainless steel WCOT and PLOT columns can be operated at temperatures in excess of 400°C. High temperature simulated distillation has been performed successfully with a macro bore WCOT column and rapid PNA (paraffin, naphthene, and aromatic) analysis with a multidimensional gas solid chromatographic (GSC) system using PLOT columns.
    Additional Material: 10 Ill.
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  • 46
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 53-55 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Plant extract ; Photochemical degradation ; Insecticides ; Volatile compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 47
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 59-61 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Glass capillary micropacked columns ; SPE sorbents ; Aliphatic hydrocarbons ; Aromatic hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 48
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 437-440 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Open tubular column ; n-Pentane ; Human breath analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new procedure, requiring expired sample volumes of approximately 2L, has been developed for the quantitative determination of n-pentane in human breath. The methodology capitalizes on the superior resolving power and separating efficiency of the open tubular capillary column and incorporates an effective prechromatographic cryofocusing technique. Molecular sieve is used to simultaneously remove moisture and carbon dioxide from breath samples which are “spiked” with an internal standard to optimize the validity of analysis. Reproducible data for both internal standard spiking (CV = 5.8%) and sample n-pentane level (CV = 3.2%) have been obtained, together with a mean recovery of 104%. Preliminary data show n-pentane levels in normal female subjects (n = 10) to range from 0.62 to 3.16 nmole/L (mean 1.76 nmole/L) and in males (n = 10) from 3.20 to 8.76 nmole/L (mean 5.66 nmole/L).
    Additional Material: 2 Ill.
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  • 49
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 501-503 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Vaporizing injectors ; Matrix effects ; Organophosphorus pesticide residues ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 50
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 539-548 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Atomic emission detection ; Pesticide residue analysis ; Multi-residue methods ; Complex foodstuff matrices ; Maximum residue tolerance levels ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high selectivity of element-specific atomic emission detection has proven suitable for screening analysis of plant foodstuffs for pesticide residues by capillary gas chromatography, especially for those foodstuffs which contain high levels of matrix compounds. The elemental composition of a peak can, furthermore, be examined by looking at the partial emission spectra recorded during a GC run. This instrumental feature prevents false positive signal interpretation as a result of high concentration levels of eluting matrix compounds.
    Additional Material: 11 Ill.
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  • 51
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 530-535 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Resolution of enantiomers ; Stereoselectivity ; Chiral stationary phase ; Derivatized cyclodextrin ; Trifluoroacetylated cyclodextrin ; Thermodynamic properties ; Derivatization ; Alcohols ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6-di-O-n-pentyl-3-O-trifluoroacetyl)- γ-cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2- and 3-hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four-carbon chain attached to the stereogenic center. For longer-chain fluoroacyl derivative groups stereoselectivity was higher for the 2- and 3-hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl-branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole-dipole contribution and some form of steric component, depending upon the shape and/or size of the solute.
    Additional Material: 3 Ill.
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  • 52
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 561-564 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Trace analysis ; Solvent effect inlet technique ; Solvent purification ; Solvent storage ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 53
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 379-380 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Natural gas ; Tetrahydrothiophene (THT) ; Odorant ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 54
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 495-500 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Retention index standards ; Benzodiazepines ; Drug screening ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An homologous series of benzodiazepine retention index standards (the R-series) has been synthesized and the gas chromatographic behavior of the series investigated on NB-54 and NB-1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R-series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R-series method was found to be generally better than that of the two other methods in both long- and short-term studies.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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