摘要:

AbstractThe scope of the headspace sampling technique for the analysis of solid samples is discussed, and the static and the dynamic headspace methods compared. Theoretical aspects relating to quantification are discussed. The paper considers both instrumental requirements and applications.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130802

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe concept of a GC solvent evaporation technique is outlined that involves a modified Programmed Temperature Vaporizing (PTV) injector. The vapor overflow technique is intended for introducing samples in large volumes of solvent by syringe injection of strongly diluted samples or by coupled LC‐GC. The liquid is introduced into a packed vaporizing chamber kept above the solvent boiling point at a pressure which is near or below ambient. The carrier gas is essentially switched off. Evaporation and discharge of the solvent vapors occurs by expansion of the vapors, driven by the solvent vapor pressure. For transferring the sapmple into the column, the carrier gas is switched on again and the vaporizing chamber heated.Compared to PTV solvent split injection, vapor overflow offers the following advantages: It automatically optimizes operational parameters, therefore facilitating its application. Losses of volatile materials are minimized by a minimal flow rate through the injector.Vapor overflow is a promising technique for transferring watercontaining eluents in coupled LC‐GC since no wettability is required and leaching of pre‐column surfaces is av

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130803

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

年代:1990

数据来源: WILEY

摘要:

AbstractPCB patterns in a new pigment brand are characterized using GC‐MS in the single ion monitoring (SIM) mode. Specific PCBs are then used as external standards for GC‐ECD quantification. The following PCB isomers or groups of isomers have to be determined (CB = chlorobiphenyl): total diCBs, 3,3′ diCB, 2,4,5‐triCB, 2,2′,4,4′‐tetraCB, 2,2′,5,5′‐tetraCB, total pentaCB, total hexaCB. Capillary gas chromatography is performed on preseparated solutions (LC) of pigment. An electron caputure detector (ECD) is used for PCB detection and quantification. Calibration is based on the peak areas of external standards and the PCB isomers in the samples, all normalized for internal standard peak areas. Total concentrations of diCB, hexaCB, or pentaCB in a sample are calculated by summing the individual PCB isomer concentrations within the correcsponding elution ranges. Determination limits lie in the range of 1 mg/PC

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130804

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe allelopathic effects of decomposing wheat straw have been known for some time. In spite of the ecological and economical importance of the subject, only a limited number of compounds have been asociated with the allelopathic activity of wheat straw. In this study the high resolution, speed of analysis, and sensitivity of capillary gas chromatography coupled with mass spectromtry (HRGC‐MS) and Fourier transform infrared spectrometry (HRGC‐MS‐FTIR) have been used in a systematic study of the composition of biologically active wheat straw extracts. Droplet counter‐current chromatography (DCCC) was used for fractionation and isolation of components. The extract components were analyzed as methyl derivatives and free hydroxyl groups were located by means of ethylation with diazoethane. Twenty compounds were identified, most of them being phenolic acids. Naphthoic acid, azelaic acid and 1,2,3,5‐tetrabromobenzene were also i

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130805

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

年代:1990

数据来源: WILEY

摘要:

AbstractLiquid gases (LG),i.e.low boiling compounds with vapor pressures below 5 bar at room temperature, are introduced as solvents for trace analyses. A system for preparin, diluting and handling LG solutions safely and conveniently in 5 to 500 μl amounts was developed as well as a syringe for direct injection of μl‐LG samples into capillary GC. Even technical grade LG are of high purity. GC/FID of LG solutions (starting at −60°C) allows the separation of volatile traces from the solvent peak:e.g., dichloromethane can be measured in the picogram

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130806

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.1240130807

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.1240130808

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.1240130809

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.1240130810

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.1240130811

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

年代:1990

数据来源: WILEY