ISSN:0935-6304    

DOI:10.1002/jhrc.1240161202

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe analysis of samples contaminated by organic compounds is an important aspect of environmental monitoring. Because of the complex nature of these samples, isolating target organic compounds from their matrices is a major challenge. A new isolation technique, solid phase microextraction, or SPME, has recently been developed in our laboratory. This technique combines the extraction and concentration processes into one step; a fused silica fiber coated with a polymer is used to extract analytes and transfer them into a GC injector for thermal desorption and analysis. It is simple, rapid, inexpensive, completely solvent‐free, and easily automated. To minimize matrix interferences in environmental samples, SPME can be used to extract analytes from the headspace above the sample. The combination of headspace sampling with SPME separates volatile and semi‐volatile analytes from non‐volatile compounds, thus greatly reducing the interferences from non‐target compounds.This paper reports the use of headspace SPME to isolate volatile organic compounds from various matrices such as water, sand, clay, and sludge. By use of the technique, benzene, toluene, ethyl‐benzene, and xylene isomers (commonly known as BTEX), and volatile chlorinated compounds can be efficiently isolated from various matrices with good precision and low limits of detection. This study has found that the sensitivity of the method can be greatly improved by the addition of salt to water samples, water to soil samples, or by heating. Headspace SPME can also be used to sample semi‐volatile compounds, such as PAHs, from compl

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161203

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe enantioselectivity of three chiral selectors, 6‐t‐butyldimethyl‐silyl‐2,3‐dimethyl‐α‐, β‐ and γ‐cyclodextrin (TB‐α‐CD, TB‐β‐CD, TB‐γ‐CD), are compared and discussed for a range of chiral test compounds. TB‐β‐CD in particular offers high enantioselectivity for a variety of chiral compounds and has the special property of excellent solubility in different alkylpolysiloxanes, including the weakly polar variety, because of its weak self‐association. To investigate the influence of the polarity of polysiloxane matrices this selector can be used at a wide range of concentrations in the most suitable polysiloxane matrices and at low separation temperatures without impairment of resolution

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161204

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

年代:1993

数据来源: WILEY

摘要:

AbstractA new packed column SFC method has been developed for the determination of phytanic acid in human blood serum. Because of the low viscosity and high diffusion coefficient of supercritical carbon dioxide, several columns can be connected in series, significantly improving separation. Series connection of columns which differ in their selectivity enables the adjustment of the total selectivity towards the individual separation problem (‘selectivity tuning’). In this instance it was possible, after transesterification into their ethyl esters, to separate all the fatty acids in human blood serum, including phytanic acid, by coupling three columns (silica, amino‐propyl, and RP8) in s

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161205

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe enantioseparation of some 2,2‐dialkyl‐4‐alkoxycarbonyl‐1,3‐dioxolane derivatives, which are important intermediates in the total synthesis of a number of biologically active compounds, was studied by means of capillary gas chromatography (CGC). The chromatographic results, obtained on columns coated with permethylated α‐, β‐ and γ‐cyclodextrin respectively, are reported. Out of sixteen compounds, thirteen could be separated with a resolution superior to 1,2. One racemate could not be separated on any of the columns. Considerations concerning the separation mech

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161206

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

年代:1993

数据来源: WILEY

摘要:

AbstractDegradation products obtained under severe alkaline stress of the drug substance ENA 713, a compound developed for the treatment of DAT (dementia of theAlzheimertype), have been identified by on‐line coupled reversed phase HPLC‐GC‐MS as 3‐hydroxyaceto‐phenone and 3‐hydroxystyrene. Their structures were proven by mass spectroscopic investigation of the products obtained by on‐column derivatization during LC‐GC transfer. On‐column trimethyl‐silylation and bromination of the degradation products during the transfer were achieved by the introduction of the reagentviathe loop‐type interface. The usefulness of the technique was further demonstrated by the on‐column methylation of carboxylic acids with diazomethane solution (using naproxen as model compound). First results are also given of the use of the liquid‐liquid extraction unit of the LC‐GC interface for extractive derivatization during reverse

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161207

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

年代:1993

数据来源: WILEY

摘要:

AbstractA polarity test mix consisting of acetophenone,N,N‐dimethylaniline, naphthalene, decanoic acid, 2‐naphthol, andn‐tetracosane was spiked onto sand, and extracted with supercritical carbon dioxide, to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvent systems and four mixed collection solvent systems were studied. When one‐component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes studied were p

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161208

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe report a feasibility study on using a microwave‐induced helium plasma atomic emission detector (MIP‐AED) as an on‐line detector in capillary zone electrophoresis (CZE). To couple CZE to MIP‐AED, we used an ion exchange membrane capillary to connect the separation capillary to the interfacing capillary. The outlet end of the interfacing capillary was placed directly in the discharge tube of the MIP‐AED system. The electroosmotic flow generated in the separation capillary carried the analytes and the electrolyte buffer solution through the interfacing capillary into the MIP‐AED discharge tube where the analytes were detected. The performance of the CZE/MIP‐AED system was evaluated with trimethyltin chloride, dimethyltin dichloride, n‐propanol, and 2‐butanone. The preliminary results indicate that the MIP‐AED can be used in CZE to provide element‐specific detectio

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161209

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

年代:1993

数据来源: WILEY

摘要:

AbstractFour poly(methyl 3,3,3‐trifluoropropyl siloxanes) with trifluoro‐propyl group content (group substitution) between 8 and 35 percent have been synthesized and characterized as stationary phases for gas chromatography in borosilicate glass capillary columns. Results are compared with those from two commercial stationary phases–a polydimethylsiloxane and a poly(methyl 3,3,3‐trifluoropropyl siloxane) with a fifty percent trifluoropropyl group content (group substitution).Retention index values,McReynoldsconstants, polarity (as defined byMcReynolds) and retention polarity (as defined byTakács) increase regularly with the trifluoropropyl group content of the stationary phase. The temperature coefficient of the retention indices of theMcReynoldsprobes, and that of the polarities, have been determined at temperatures between 60 and 180 °C. Specific retention volumes do not follow the linear dependence on trifluoropropyl group content observed for retention indices or polarities. Substances with electron‐donor groups show maximum retention for a trifluoropropyl group content ofca30%, whereas the retention of hydrocarbons, halogenated compounds, and alcohols decreases as the degree of trifluoropropyl group substitution increases from 0 to 50%. It is felt that a polysiloxane with a trifluoropropyl group content ofca30 to 35% would be the best choice for the separation of ketones, nitro compound

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161210

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe triacylglycerol composition of olive oil samples has been determined by stereospecific analysis after partial hydrolysis with ethyl magnesium bromide, derivatization, preparative chiral HPLC, transesterification, and GC quantitation of fatty acid methyl esters. The data obtained for positionsn‐2 were compared with those from capillary GC analysis of monoacylsn‐2‐glycerols after enzymatic lipolysis of triacylglycerols.The determination of triacylglycerols collected by silver ion HPLC and quantified (as fatty acid methyl esters) by GC, together with direct GC analysis on a polar column, have then furnished a comprehensive picture of the triacylglycerol content of oliv

ISSN:0935-6304    

DOI:10.1002/jhrc.1240161211

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

年代:1993

数据来源: WILEY