ISSN:0935-6304    

DOI:10.1002/jhrc.1240160802

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

年代:1993

数据来源: WILEY

摘要:

AbstractA system is described that allows the introduction of large volumes of water samples in capillary GC. Water elimination is carried out in the solvent split mode in a PTV injector with a packed liner. Two ways of separating water and analytes,i.e.evaporative and non‐evaporative (solid‐phase extraction), are compared. Sampling in the solid‐phase extraction mode is favorable both in terms of recovery as well as with regard to sampling time. Quantitative recovery is obtained for priority pollutants ranging in volatility from dimethyl‐phenol to phenanthrene. Losses occur for more volatile compounds, but even for these compounds the repeatability of the recoveries remains acceptable. With the system described here, water samples up to at least 1 ml of water can be directly analyzed. The detection limits are in the sub‐

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160803

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe inertness of injector inserts and insert packing materials, such as glass or fused silica wool, is tested by a procedure based on split injection and rapid isothermal chromatography. Resulting sharp peaks sensitively reveal peak deformation resulting from adsorptivity, acid/base interaction, and excessive retention power. Degradation of labile components is detected by loss of material and degradation products. Adsorptivity was no problem on injecting 300 ng amounts. Degradation only occurred for raw wools; however, the retention power of some wools seemed unnecessarily high. On injection of smaller quantities, degradation remained similar, but adsorptivity increased significantly.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160804

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

年代:1993

数据来源: WILEY

摘要:

AbstractCapillary supercritical fluid chromatography (SFC) with carbon dioxide as the mobile phase has been used to separate a mixture of limonoid standards. Chromatographic conditions were optimized to enable analysis of plant extracts. The seed ofAphanamixis polystacha(Meliaceae) and the stem bark ofHarpephyllum caffrum(Anacardiaceae) were extracted with hexane and the extracts were analyzed by SFC to demonstrate the potential of the technique as a screening tool. SFC analysis indicated the presence of limonoids in the hexane extract of the bark ofEntandrophragma delevoyii(Meliaceae). One limonoid and two protolimonoids isolated from the extract were separated by SFC.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160805

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

年代:1993

数据来源: WILEY

摘要:

AbstractA method has been developed for the quantitative extraction of nitrotoluenes (2,3‐dinitrotoluene, 2,4‐dinitrotoluene and trinitrotolugene) from water using a BakerbondTMphenyl sorbent. The average solid phase extraction recoveries for spiked standards ranged from 80 to 95 percent for reagent water and 52 to 95 percent from well and surface water in the low ppb and ppt levels. After the nitrotoluenes had been trapped on the solid sorbent they were quantitatively eluted using SFE. Adding toluene to the extraction cell increased the rate of extraction, but did not improve analyte recovery versus unmodified CO2. The extracts were analyzed off‐line with GC–ECD using an internal standard. Extraction losses were due to analyte breakthrough, and not from poor SFE recoveries. This demonstrates that supercritical fluid extraction is a suitable elution technique for analytes trapped on solid phase extraction sorbents.Also, a method for the direct on‐line coupling of SPE to GC, using SFE, has been developed and evaluated. Supercritical CO2is ideal for directly coupling SPE to GC, since carbon dioxide is a gas under ambient conditions. One potential problem of on‐line SPE–SFE–GC is the presence of residual water trapped on the active sites of the Bakerbond13phenyl sorbent. This problem was dealt with by using a split interface previously described byHawthorne. From the results of this study, the relative standard deviation of the on‐line SPE–SFE–GC interface was determined to be between 4 and 10 percent. In addition, there was no significant difference in the precision of the method with or without the use of an internal standard. A calibration curve was also constructed (r2= 0.995) from spiked controls, demonstrating that the m

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160806

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe combination of high performance liquid chromatography interfaced on‐line with multidimensional gas chromatography (HPLC–GC–GC) is described. The HPLC column was interfaced to the GC via an on column interface, with automated pneumatic control of solvent evaporation and GC column switching. Cryogenic cold trapping was used for analyte focusing at the head of the first, non‐polar GC capillary column and optionally at the head of the second, polar column. The determination of stilbene hormones in corned beef as their methylated derivatives by flame ionization detection is de

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160807

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe introduction of quality standards for vegetable oil methyl esters is gaining in importance due to their increased use as diesel fuel substitutes and as technical products. Free and esterified sterols, the main constituents of the unsaponifiable matter in vegetable oils, are recovered in vegetable oil methyl esters and may influence the technical properties of vegetable oil methyl ester products. A rapid gas chromatographic method for the qualitative and quantitative determination of free and esterified sterols in vegetable oil methyl esters has therefore been developed.The concentration of the free sterols as well as their qualitative and quantitative composition and the concentration of the sterol esters have been determined in rape seed oil methyl ester samples by GC–FID. Prior to analysis, the free sterols were silylated withN,O‐bis(trimethylsilyl)trifluoroacetamide with 1% of trimethylchlorosilane; betulinol was used as an internal standard. Calibration was performed by analysis of standard solutions containing β‐sitosterol, cholesteryl stearate, and betulinol. The reproducibility of the quantitative results has been evaluated by repeated injections of the same test solution and by repeated complete analysis of the same

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160808

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe fatty acid composition of the seed lipids of plants, in contrast to leaf lipids, may contain highly specific unusual fatty acids, which are often correlated to plant family. For example, petroselinic acid is typical for the Apiacea family, cyclopropene fatty acids are typical for the Malvaceae family, and cyclopentene‐ring containing fatty acids for the Flacourtiaceae family. Other fatty acids may be characteristic for certain sub‐families or only for certain species of plants within a family or genus. γ‐Linolenic acid, Δ5–18:3 and Δ5–20:3 fatty acids and others may occur in several plant families, but are still linked to certain related species only. They can be analyzed by high‐resolution capillary GLC. Particularly interesting is the situation in the family Ranunculaceae. GLC fingerprints of fatty acids are shown that may indicate a closer or less close relationship between species with

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160809

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

年代:1993

数据来源: WILEY

摘要:

AbstractPolynuclear aromatic hydrocarbons (PAHs) are recovered from a soil with a high carbon content (ca.50%) with supercritical fluid extraction (SFE) as well as with conventional Soxhlet extraction. The influence of temperature and modifier volume on SFE efficiency and the effect of a combined liquid/solid trap for analyte collection are investigated in this study. Such traps, which make analyte collection and clean‐up possible in one step, are compared with conventional analyte collection in pure organic solvents. A comparison between reproducibility and efficiency of SFE and Soxhlet extraction is presente

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160810

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

年代:1993

数据来源: WILEY

摘要:

AbstractAn homologous series of benzodiazepine retention index standards (the R‐series) has been synthesized and the gas chromatographic behavior of the series investigated on NB‐54 and NB‐1701 capillary columns. The compounds were stable, exhibited symmetrical peak shapes, and fairly linear retention behavior was observed on both columns. The series can be coinjected with every sample to enable the high precision analysis of toxicological samples; screening for 20 benzodiazepine drugs was possible in 23 minutes (including cooling). The R‐series method was compared with a retention index method based on a series of benzodiazepine drugs as standards and with a method employing relative retention times. The precision of the R‐series method was found to be generally better than that of the two other methods in both long‐ and short

ISSN:0935-6304    

DOI:10.1002/jhrc.1240160811

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

年代:1993

数据来源: WILEY