摘要:

AbstractHigh resolution gas chromatography has greatly changed the field of polychlorinated biphenyl (PCB) analysis. From a rough estimation of the total PCB concentration on packed column GC, the development of commercially available fused silica capillary columns in the late 1970s and early 1980s has advanced the analysis of PCBs to a point where they can be accurately measured as separated congeners. The state‐of‐the‐art of PCB analysis in the 1990s is routine isomer‐specific analysis with multi‐column techniques using long (0.25 mm) columns. A broad spectrum of commercially available stationary phases have been completely characterized with regard to their PCB elution

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180302

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of different polysiloxane solvents on the efficiency and stereoselectivity of columns coated with mixtures of heptakis (2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin and the polysiloxanes was investigated. Generally, the enantioselectivity increased with decreasing polarity of the silicone solvent and/or increasing cyclodextrin concentration, with some exceptions. Thermodynamic investigations showed that a change of the diluting phase or the cyclodextrin concentration affects entropy as well as enthalpy differences between the diastereomeric cyclodextrin/solute complexes. As a consequence, a certain cyclodextrin/polysiloxane combination is superior to another only at a part

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180303

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe use of 10%, 1%, and 0.1% ammonia in helium as carrier gas was investigated as a means of improving poor chromatographic peak shape often associated with low level determinations of amine compounds using thin film capillary columns. The 1% ammonia in helium was found suitable for improving the peak shape of sterically unhindered amine compounds, such as urethane and certain aliphatic primary amines, during gas chromatographic analysis on thin film columns. There was a negligible effect on the peak tailing arising on thick film columns. The 0.1% ammonia in helium was suitable, but not as efficient as the 1% ammonia in helium, in eliminating the peak tailing associated with low level analysis of amine compounds. The signal‐to‐noise (S/N) ratio improved from<1 using helium carrier gas to 20–25 (for certain test amine compounds) using 1% ammonia in carrier gas. The 10% ammonia in helium carrier gas had an effect on the chromatographic performance similar to that of the 1% ammonia in helium, but the baseline level was very high and this mixture was not used in further st

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180304

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

年代:1995

数据来源: WILEY

摘要:

AbstractSolid phase microextraction (SPME) was used as the sample introduction technique for high‐speed isothermal GC. An injector dedicated for SPME fiber injection was designed and built. The injector was operated in two modes, continuously heated and flash heated. The latter mode proved to be better for high‐speed separations. The injector was then used for sample introduction in separation of BTEX. When sampling directly from water with a fiber having a 56 μm thick poly(dimethylsiloxane) coating, the BTEX components were separated under isothermal conditions inca. 18 s. A fiber with a thinner coating (15 μm) enabled the separation to be completed in ca. 12 s when sampling from headspace. In both cases the results were highly reproducible, as measured by the estimated values of the relative standard devi

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180305

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

年代:1995

数据来源: WILEY

摘要:

Abstractn‐Alkanes and fatty acid methyl esters have been chromatographed on four capillary columns of different polarity (LM‐1 (100% polydimethylsiloxane), CB‐225 (25% cyanopropyl, 25% phenyl polysiloxane), LM‐100 (immobilized polyethylene glycol), and BPX‐70 (70% cyanopropyl polysiloxane)) with the goal of identifying the major fatty acid methyl esters obtained by derivatization of vegetable oils. Chromatographic retention data were employed for the construction of a three‐dimensional Kováts retention index system and for the elaboration of a table of equivalent chain l

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180306

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

年代:1995

数据来源: WILEY

摘要:

AbstractA micellar electrokinetic chromatography method is presented for the determination of the partition coefficient for the distribution of nonpolar and moderately polar solutes between the micelle and the aqueous phases in aqueous micellar solutions. In comparison with the literature the method is, theoretically and experimentally, the most straightforward for this application. An equation is derived for the determination of the partition coefficient in a coated fused silica capillary, with neglible electroosmotic flow, from simple measurements of the migration times of solutes and a marker for micelle migration. The advantages and limitations of this method are discussed. The method is tested by using sodium dodecylsulfate (SDS) surfactant and naphthalene, benzene, toluene, and phenol solutes. Micellar electrokinetic chromatography in coated columns isideally suited for the separation of hydrophobic solutes in aqueous samples.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180307

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

年代:1995

数据来源: WILEY

摘要:

AbstractAnions of alkylphenols have very similar electrophoretic mobilities in CZE owing to their very small differences in size and the narrow range of their pKavalues. By studying electrophoretic mobility as a function both of pH and of the amount of acetonitrile in the electrolyte solution, optimum separation conditions were determined. It was possible to separate a group of methyl‐substituted phenols, including several positional isomers. Mixtures containingn‐propyl and isopropyl phenols and 1°, 2°, and 3° butylphenols could be re

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180308

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe following carbamate derivatives of cyclodextrins (CDs) were prepared as novel chiral stationary phases for capillary gas chromatography: hexakis(2,6‐di‐O‐pentyl)‐α‐cyclodextrin hexa(3‐n‐propyl, 3‐isopropyl, and 3‐phenylcarbamate), heptakis‐(2,6‐di‐O‐pentyl)‐β‐cyclodextrin hepta(3‐n‐propyl, 3‐isopropyl, and 3‐phenylcarbamate), and octakis(2,6‐di‐O‐pentyl)‐γ‐cyclodextrin octa(3‐n‐propyl, 3‐isopropyl, and 3‐isopropyl, and 3‐phenylcarbamate). Metal capillary columns coated with these stationary phases resolved many kinds of racemic mixture. In general, they were especially effective towards polar compounds such as free alcohols, amines, and epoxides. The types of sample which were effectively resolved depended on the cavity size of the CD: α‐CD derivatives were specifically effective toward compounds having linear alkyl chains, and β‐CD derivatives toward compounds with phenyl groups. The results indicate that chiral separation with the cyclodextrin carbamates depends on the formation of inclusion complexes and also on the hydro

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180309

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

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180310

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

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180311

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

年代:1995

数据来源: WILEY