摘要:

AbstractThe separation of the principal inorganic anions (bromide, carbonate, chlorate, chloride, fluoride, nitrate, nitrite, sulfate, phosphate) has been achieved using a capillary electrophoresis system with indirect UV detection at 260 nm. Several types of cationic surfactants (quaternary ammonium, phosphonium or methonium) were tested as electroosmotic flow modifiers and added to a chromatebased buffer prepared from potassium dichromate. The influence of many physicochemical parameters such as nature and concentration of cationic surfactant, buffer pH, dichromate concentration buffer, voltage and temperature upon the migration time of an analyte anion, peak efficiency, asymmetry factor, and finally resolution has been investigated. A linear relationship between the corrected area and the anion concentration in the 2.5–50 ppm range was obtained, thus allowing the quantitative analysis of anions in mineral water. Finally, by increasing the hydrodynamic injection time, the separation of inorganic anions at a low concentration level of 50 ng/ml was achieved without any loss of resolutio

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAn 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 forn‐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

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractSoxhlet (methanol) and SFE extraction with carbon dioxide in the presence of modifiers at different temperatures (100–200°C) for the extraction of atrazine and its main metabolites from a soil sample were compared. The most effective extraction conditions for both atrazine and its metabolites (i.e.deethylatrazine and deisopropylatrazine) were Co2modified with 20% molar methanol‐trifluoroacetic acid (MeOH‐TFA) (TFA 0.65M in MeOH) at 100°C, leading to an extraction efficiency comparable with that of Soxhlet extraction with MeOH for atrazine andca.20% higher for its main metabolites. The relative standard deviation (RSD) of SFE was lower than that obtained by Soxhlet extraction, probably because of less interference in the cGC‐NPD determination. All the other modifiers evaluated (acetone, triethylamine, and methanol) were less effective than MeOH‐TFA for the extraction of atrazine and its metabolites from a soil sample, even at high molar concentrations (20%) and use of higher extraction temperatures (200°C). These results indicate the importance of matrix effects and the need of the selection of an appropriate modifier in order to obtain quantitative extrac

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractSplit injection of 1‐pentanol headspace on to raw or treated fused silica tubing yields information on the characteristics of its surface (silanol concentration, polarity, adsorptivity). Fused silica tubing from three sources was compared. The effect of various leaching and etching procedures used for column preparation was studied, as was the stability of uncoated fused silica precolumns towards water and some organic solvent

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractAlumina‐coated porous layer open tubular (PLOT) columns are widely used for analyses of light hydrocarbons (C1to C6). There is, however, a need for improved selectivity for complex analyses such as the determination of impurities in high purity petrochemical products. Some commercial alumina PLOT columns do not have sufficient selectivity for such analyses. The selectivity of four commercial alumina PLOT columns is evaluated for analyses of propylene and ethylene, and differences in column selectivity discussed. Requirements of column selectivity and retention are presented for several applications including the analysis of refinery gas, transformer oil gas, and fuel ga

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe headspace gas in static headspace gas chromatography contains mostly saturated water vapor. In the case of the cryofocusing enrichment technique this may cause baseline distortion in the early part of the chromatogram or may even lead to ice‐plugging of the capillary column. A water‐trap is described in which the water vapor is removed from the headspace gas before entering the cryo‐trap. The water trap is packed with lithium chloride on a porous support and is regenerated after each analysis by heating under backflush conditions. It therefore can be used for automatic operation. Data are given for the precision and accuracy, and some practical examples, for environmental and flavor analysis are

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractThe ester portion of epicuticular waxes of tall fescue (Festuca arundinaceaSchreb.) is composed of mixtures of homologous series of fatty acids esterfied with fatty alcohols. GC analyses of natural esters gave rise to the separation of several compounds of different chain length. To identify and quantify individual components in the mixture, GC/MS analyses were carried out, and the mass spectra of each peak were recorded and analyzed for characteristic ions. This approach permitted a comparison with data obtained from classical methods using GC analysis of acid and alcohol moieties obtained by hydrolysis.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractA method is presented for the identification and quantification of C2‐substituted benzothiophenes in crude oil. The method will enable analysis of the pattern of these compounds, for example as a basis for differentiating crude oils from one another (fingerprinting) and for investigation of their suitability as indicators of oil maturity. Here results are reported for five crudes from Iraq, Venezuela, Saudi Arabia, the former Soviet Union, and the North Sea. The aromatic fraction of the crudes was oxidized and the dioxides of the heterocycles separated according to the number of carbon atoms in the side chains. The final separation was by capillary GC with atomic emission or flame ionization detection. A fluorinated analog was synthesized and used as internal standard. The concentrations of 2,3‐, 2,4‐, 2,7‐, and 3,7‐dimethylbenzothiophene ranged between 11 and 272 ppm. Three other dimethylated benzothiophenes present in lower amounts were also i

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

摘要:

AbstractOur GC‐MS method for the simultaneous quantitation of sugars and acids as their silyl(oxime) derivatives, from one solution by one injection, has been extended to the reproducible determination of high molecular weight compounds sensitive to decomposition yet requiring a high evaporation temperature (e.g.chlorogenic acid and rffinose) and for the quantitation of the decomposition products of pectin (i.e., for the determination of galacturonic acid at low ng levels in the presence of a 10–100 fold excess of glucose eluting just before the acid). The optimized GC procedure has been used for quantitation of the sugar and acid (including chlorogenic acid) composition of potato samples, and for the determination of the increasing amount of the decomposition products of pectin substances in apple pulp after different storage ti

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240190111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1996

数据来源: WILEY