摘要:

AbstractTrichloroacetic acid (TCA) is an atmospheric oxidation product of airborne C2‐chlorocarbons and a widespread air pollutant. It was widely used as a herbicide in the fifties and sixties, in some countries, still today. It occurs in the foliage of conifers and deciduous trees of mountain forests in Germany, e. g. the Black Forest, the Northern Alps or the Erzgebirge. Quantitative determination in the ppb‐range is achieved by gas chromatography using thick film capillary columns and electron‐capture detection. The levels in spruce needles at two forest sites correlate with the extent of needle loss. The data are supportive of the hypothesis that TCA is causally involved in the induction of mountain forest de

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131102

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

年代:1990

数据来源: WILEY

摘要:

AbstractHigh efficiency liquid chromatography (LC) on both coupled conventional columns and long micro‐LC columns, both with diode array detection, has revealed the presence of some hitherto unknown compounds in hop extracts. Proof is advanced that ethanol extracts of hops contain iso‐alpha acids.The elution order of thecis‐transpairs of the iso‐alpha acids, and the separation of the alpha acids from the deoxyalpha acids, is reversed by switching from methanol to acetonitrile in the reversed phase solvent system.An LC solvent system giving higher resolution (higher selectivity factor) of the iso‐alpha acidcisandtransstereoisomers is obtained by adding magnesium salts to t

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131103

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

年代:1990

数据来源: WILEY

摘要:

AbstractAnalysis of low concentration polymer additives has been a challenging problem. The commonly used methods of analysis involve the initial extraction of polymer additives with solvents, often in a Soxhlet apparatus, followed by liquid, size exclusion, or gas chromatography. This paper describes the on‐line super‐critical fluid extraction (SFE)‐supercritical fluid chromatographic (SFC) determination of different additives from low density polyethylene. Cryogenic collection was used as an interface between SFE and SFC to focus the extraction eluate before transfer to an analytical SFC column for quantitative ana

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131104

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

年代:1990

数据来源: WILEY

摘要:

AbstractA new, versatile, and low cost on‐line LC‐GC interface has been devloped for the fast and reliable introduction of large volume samples into a cappillary GC column without using the conventional retention gap. PAHs in soot were analyzed by on‐line normal phase HPLC‐capillary GC. A glass, vial‐shaped on‐line concentrator provides a zone for solvent evaporation and sample concentration. Large volumes of HPLC eluate can be concentrated with the on‐line concentrator and then transferred directly into the cappillary column. Trace levels (<10 ppb) of PAH compounds can be efficiently concentrated with the on‐line concentrator and determined without loss o

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131105

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe use of capillary column gas chromatography for drug screening in forensic toxicology has become increasingly widespread. Screening procedures however are often lengthy and unsuitable for rapid confirmatory or quantitative applications. In order to develop a practical scheme for confirmatory/quantitative analysis, we have optimized a series of temperature profiles to allow the rapid quantitative determination of a wide range of acid/neutral and basic drugs in extracts from post mortem fluids and tissue. The appropriate profile is selected based on the retention index on a standard crosslinked methyl silicone column used to screen extracts. The use of a 5% phenyl methyl silicone phase allows complementary identification, and allows the separation of some pairs of compounds with identical retention indices in the screning procedure.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131106

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn experiment has been designed to study the thermal degradation of thermolabile compounds caused by various injection techniques. The four carbamate pesticides aminocarb, bendiocarb, carbaryl, and dioxacarb decompose thermally into methylisocyanate and the corresponding phenol. The carbamets and the phenols arising from them were separated on a 25 m SE‐54 fused silica column; all compounds exhibited sharp peak shape indicating that the degradation observed took place completely within the injector.When cold on‐column injection was employed no thermal degradation was observed whereas with hot splitless injection at 220°C decomposition of the carbamates was almost complete.PTV injection was found to produce intermediate results. When packed with glass wool and operated with glass wool and operated with starting temperatures lower than the boiling point of the solvent, decomposition was found to be almost complete. Applying isothermal conditions at 140°C (30°C above the boiling point of toluene) aminocarb and bendiocarb underwent only slight decomposition while carbaryl and dioxacarb were about half degraded. Results from PTV injection with an empty insert resembled those obtained using cold on‐column injection and in this mode the application of temperatures up to 200°C resulted in no visible degradation. This can be explained by the short residence time of the sample in the

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131107

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

年代:1990

数据来源: WILEY

摘要:

AbstractClearly, the usefulness of a computer‐aided column design program will depend on its ability to predict quickly and accurately, a design which will yield chromatograms closely approximating those obtained experimentally. Such a computer model for designing and specifying operating conditions for optimum performance of either single or serially coupled columns with different stationary phases is described herein. Tests have been performed in order to verify the accuracy of the model.In addition to single column optimization and the design of column combinations which can be used to achieve separations difficult or impossible on a single phase alone, the model has proven quite useful as an aid to the design and development of multicolumn analysis procedures that involve critical timing of valve‐switching sequen

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131108

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

年代:1990

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131109

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

年代:1990

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131110

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

年代:1990

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240131111

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

年代:1990

数据来源: WILEY