摘要:

AbstractThis contribution describes GC/MS analysis of natural petroporphyrin extracts containing alkylporphyrins either as vanadyl complexes or as demetalated free bases. The combination of high temperature glass capillary gas chromatography with mass spectrometry allows, for the first time, direct determination of electron impact mass spectra of separated alkylporphyrins, making additional purification and derivatization unnecessary. The separation is carried out on glass capillary columns coated with the high temperature‐stable medium polar, OH‐terminated, polysiloxane phases PS 086 and OV‐225‐OH. The paper gives detailed working directions for the preparation of the high temperature GC/MS‐interface, and of the high temperature stable OV‐225‐OH columns (max. working tempe

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110202

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

年代:1988

数据来源: WILEY

摘要:

AbstractA new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV‐1‐vinyl, SE‐54, and OV‐1701‐vinyl. This methodology includes the application of the moderately polar stationary phase OV‐1701‐vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory‐produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV‐1701‐vinyl deactivation layer to both crosslinking and surface bonding in the immobilization pr

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110203

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

年代:1988

数据来源: WILEY

摘要:

AbstractA porous polymer is deposited on the inner wall of fused silica capillary columns. The retention characteristics of this porous polymer were evaluated and found to be comparable with Porapak Q. The porous polymer has a high retention volume which enables the separation of permanent gases at ambient temperatures or higher. The hydrophobic character of the porous polymer allows the injection of water containing samples without changing retention due to adsorption of water. The inertness of the porous polymer allows the elution of a range of apolar and polar compounds. The maximum temperature of the porous polymer was estimated to be 250°C. With this new type of capillary column, high resolution separations are obtained in combination with short analysis times

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110204

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

年代:1988

数据来源: WILEY

摘要:

AbstractBy using gas chromatographic intermediate surface testing to study the surface properties of fused silica capillary tubing, the reversible adsorption of aldehydes and ketones on the fused silica surface has been observed for the first time. It is shown that this interaction can arise from the preferential interaction of carbonyl functional groups at bonded silanol sites on the surface. It is further shown that simple test mixtures containing aldehydes or ketones can be used to probe the concentration of water and bonded silanols on the surface and thus to evaluate capillary manufacturing processes and thermal and chemical surface treatments.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110205

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

年代:1988

数据来源: WILEY

摘要:

AbstractA fully automated on‐line HPLC‐HRGC instrument is described. Samples are loaded into an HPLC autosampler. Pre‐separation is carried out, automatically transferring the previously determined HPLC fraction to GC. Total HPLC fractions are introduced into GC, using the on‐column or the loop‐type interface, depending on the solvent evaporation technique applied. The HPLC column is automatically backflushed with a suitable solvent during GC analysis. The instrument was used for analyzing heroin metabolites, particularly morphine, in urine samples. Raw urine extracts were injected into HPLC and analyzed by GC

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110206

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn comparison with conventionally packed HPLC columns, from a theoretical point of view, open capillary liquid chromatography (OTLC) systems offer a number of advantages like high plate numbers and short analysis times. On the other hand, drastic changes have to be made to the instrumentation. In particular, the contribution to band broadening by the chromatographic equipment must be considerably reduced. In the present study an OTLC system was developed and evaluated, which yields satisfactory results for 26 μm i. d. columns. The determination of the contribution of the chromatographic equipment to the total band broadening is discussed

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110207

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

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper describes the design of a new, versatile, and low‐cost on‐line LC‐GC interface that allows the fast and reliable introduction of large sample volumes onto a capillary GC column. The sample introduction procedure consists successively of: evaporation of the entire sample (LC fraction), selective removal of the solvent and simultaneously cold‐trapping of the solutes, splitless transfer of the solutes to the GC column, on‐column focusing, GC separation and detection. Quantitative and qualitative aspects of various experimental parameters are evaluated and optimum conditions are reported. The applicability of the method is demonstrated on a synthetic aqueous sample of chlorinated p

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110208

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe analysis of complex mixtures, such as essential oils requires high resolution chromatographic separation and even the use of very efficient columns cannot prevent the overlapping of certain peaks. This means that it is very difficult to obtain high quality mass spectra when the sample contains numerous constituants. The pre‐separation by column or preparative GC leads to a considerable loss of material and, often, to the formation of artefacts. In order to overcome some of these difficulties, we have built a simple multi‐column system that is connected to an MS‐MS instrument. Two independent chromatographs equipped with capillary columns were connected. The interface, which consists of a modified PTV injector, gives the possibilities of direct transfer, back‐flushing, heart‐cutting, intermediate cold trapping, trace enrichment and selective sample introduction. These operations are controlled by a switching valve system (DANI‐MFC 393 unit). The chromatographic system was first connected to a MS‐MS instrument which may result in high MS and collision activat

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110209

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

年代:1988

数据来源: WILEY

摘要:

AbstractDifferent designs of injection and restriction devices for capillary supercritical fluid chromatography (SFC) have been investigated with respect to their practical applicability and usefulness for reproducible and accurate qualitative and quantitative analyses. In combination with a self‐made instrument a fast switching valve is preferable as an injection device compared to a split‐injector, and an integral restrictor made from the end of the fused silica (FS) separation column was superior to a linear restrictor made by coupling a small diameter FS‐column to the separation c

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110210

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

年代:1988

数据来源: WILEY

摘要:

AbstractNarrow‐bore column liquid chromatography coupled on‐line with capillary gas chromatography (LC/GC) is used for the determination of polychlorinated biphenyls (PCBs) in sediment via a heart‐cutting technique. This method is compared with a method in which two off‐line column clean‐up steps are used with subsequent analysis by capillary gas chromatography. For the LC/GC analysis the recovery of PCBs was 90–100%. For two sediment samples from the river Meuse the LC/GC and the other, more laborious method showed goo

ISSN:0935-6304    

DOI:10.1002/jhrc.1240110211

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

年代:1988

数据来源: WILEY