ISSN:0935-6304    

DOI:10.1002/jhrc.1240150202

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe operating characteristics of a solventless injector for packed column supercritical fluid chromatography are described. Successful operation depends on the difference between the volatilities of the analytes and the solvent or matrix being sufficient for their separation by gas purging in a thermostatted precolumn, and also on the existence of an effective re‐focusing mechanism at the head of the analytical column for the sample dissolved in liquid or supercritical fluid carbon dioxide. The latter is easily achieved in density programmed operation by stationary phase trapping at low fluid densities or phase ratio trapping by changing the temperature at low to moderate fluid densities. The solventless injector can easily accommodate sample volumes from 1–100 μl and is easily adapted for in‐line derivatization using reagents which can, after reaction, be eliminated by gas purging. For general purposes the solventless injector can be used to overcome most of the problems encountered when rotary valve loop injectors are used with small bore packed columns, and will probably replace this type of injector as the injector of choice for supercritical fluid chromatography with mobile phases of low po

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150203

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

年代:1992

数据来源: WILEY

摘要:

AbstractDuring introduction of an LC fraction into the sample loop of the loop‐type interface mixing occurs between the fraction of interest and the material previously eluted from the LC. Such mixing may not only result in losses of the solute material of interest, but also in contamination of the fraction of interest with material from which it was supposed to have been isolated. Experimental determination of the extent of mixing has led to the conclusion that whereas the effects are negligible under some conditions, in some circumstances the mixing can cause severe problem

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150204

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

年代:1992

数据来源: WILEY

摘要:

AbstractA method has been developed for the collection and analysis of polar and non‐polar C4‐C14hydrocarbons involved in the formation of photochemical smog. Enrichment of hydrocarbons from both polluted and unpolluted areas has been achieved with three‐stage traps packed with carbon adsorbents of different surface area; the use of a home‐made desorption unit employing cryofocusing then enables the determination of the compounds by HRGC‐FID. Two‐stage traps filled with graphitic carbon have been used prior to GC‐MS identification and quantitation of compounds producing overlapping peaks.The methodology has been tested in the urban area of Rome and in a pine forest, and more than 140 different compounds identified and quantitated. Many of the constituents were found to be oxygenated, either formed by photochemical reactions or of anthrop

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150205

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

年代:1992

数据来源: WILEY

摘要:

AbstractGrass forage samples with different fiber content and composition, and their fibrous fractions, have been analyzed by pyrolysis – gas chromatography with ion trap detection. The identities of the pyrolysis fragments indicated their origin to be carbohydrates, lignin, and nitrogen compounds. Comparison of the resulting quantitative data by factorial variance revealed pyrogram peaks attributable to neutral detergent fiber, cellular contents, and lignin. Quantitative pyrolysis data from these components showed the same trends as those recorded by the method ofGoeringandVan Soest[1

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150206

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

年代:1992

数据来源: WILEY

摘要:

AbstractAn atomic emission detector has been evaluated for the estimation of C:H and C:N ratios of compounds eluted in gas chromatography. When C:H and C:N ratios were estimated using external reference compounds, the greatest accuracy was obtained when the quantity of the reference compound was similar to that of the analyte of interest.The accuracy of the C:H and C:N ratios determined was also affected by the molecular structure of the reference compound. C:H ratios of the greatest accuracy were obtained by using reference compounds having structures similar or close to those of the compound of interest; this was not always so for C:N ratios.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150207

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

年代:1992

数据来源: WILEY

摘要:

AbstractGC‐MS with negative ion chemical ionization has been used to detect anabolic estrogens (diethylstilbestrol, dienestrol, hexestrol, and 17β‐ and 17α‐estradiol) in bovine muscle tissue. After hydrolysis and extraction, purification by column chromatography, and derivatization, the detection limit for the estrogens is better than

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150208

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

年代:1992

数据来源: WILEY

摘要:

AbstractOrganochlorine pesticide residues have been extracted from samples of animal feed by a solid phase extraction clean‐up procedure using an octadecyl‐bonded column. The proposed method gave recoveries ranging from 70 to 100 % for ppb levels of the fifteeen pesticides studied. Analytes were identified by dual‐column capillary gas chromatography employing DB‐1 and DB‐1701 columns in parallel; identities were confirmed by calculation of retention indexes with the cubic spline interpolati

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150209

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

年代:1992

数据来源: WILEY

摘要:

AbstractResearchers using electron capture for the detection of explosive vapors currently claim the ability to detect the presence of RDX in Semtex – a plastic explosive comprising hexahydro‐1,3,5‐trinitro‐1,3,5‐triazane (RDX) in a matrix of styrene‐butadiene copolymer and hydrocarbon oil. The vapor pressure of RDX at room temperature is 0.006 ppb, and therefore well below the detection limit of electron capture detection (ECD). The positive response generated by ECD is, consequently, not from the presence of RDX, but from some other component.This paper describes the extraction and identification of several compounds in Semtex, along with the determination of which is responsible for the positive response of an ECD‐based detector.From the results of supercritical fluid extraction and off‐line gas chromatography combined with electron capture and mass spectrometric detection, it has been concluded that ethylene glycol dinitrate is the component responsible for the positive ECD response. This conclusion is based on the requirements necessary for ECD detection,i.e.electronegativity, and a sufficient vapor pressure. The other compounds present were eliminated as possible choices because they either can not be detected by an ECD or do not have sufficient vapor pressure under amb

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150210

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

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper describes the experimentally determined linear temperature programmed gas chromatographic retention behavior of hundreds of gasoline range hydrocarbons and chlorinated hydrocarbons on a cross‐linked 100% polydimethylsiloxane stationary phase. The retention indices of additional compounds which were not available as pure standards were measured in a synthetic gasoline after they had been positively identified by matching mass and infrared spectra.The experimentally determined retention information has been used to estimate the retention indices of additional compounds by extrapolation or interpolation of plots of carbon number against retention index of homologs.Isothermally determinedKovatsretention indices of compounds measured on 100 % polydimethylsiloxane have been taken from the literature and converted to linear temperature programmed retention indices using the method ofGuan et al[11]. For many of these compounds, an experimentally determined linear temperature programmed retention index was measured: agreement between experimental and converted values was excellent.In total, retention indices are presented for 480 compounds, including all possible alkylbenzenes containing ten or fewer carbon atoms, and over 150 monoenes and dienes. The effect of column pressure and the average linear velocity of the helium carrier gas on retention index and order of elution is described and discusse

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150211

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

年代:1992

数据来源: WILEY