摘要:

AbstractA Method has been developed for the separation and enrichemen of there non‐ortho, eight mono‐ortho, and di‐ortho substituted polychlorinated biphenyls (PCBs) from Aroclor formulations and environmental samples. The fractionation is accomplished using high performance liquid chromatography (HPLC) with a 2‐(1‐pyrenyl)ethyldimethylsilysily silca column. GC‐MSD with an optimized temperature program was used for quantitation, Hexane, pentane, cyclohexane, iso‐octane, and 2‐propanol were tested as a mobile phase for the isolation of the thirteen target PCBs in a Aroclor 1242, 1254, and 1260 (1:1:1) misture, Pentane at room temperature with a slow rate of 0.7 ml/min is the condition of choice. The average recovery of thirteen target PCBs spiked in the Aroclor mixture is 99.5% with an average relative standard deviation of 4.5%. The average method detection limit is 8pg/μl. Targer PCBs in the reference solis, incinarator ash, and sediment sampl

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200102

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

年代:1997

数据来源: WILEY

摘要:

Abstract(not readable) fully autimated purge and trap system has been developed for (not readable) detemination of volatile wine components. The proposed system consists of sampler, a purge and trap instrument, and a GC, (not readable) steps, from the uptake of the infiltrated wine from the sampler (not readable) to the printout of the intergrated chromatograms, proceed(not readable), Typical problems occurring when analyzing polar analytes by the classical purse and trap approach have been specifically addressed. The system has been desiggned to handle such difficult (not readable) analytes. Efforts have been made to improve the reproducibility and the carry‐over of these analytes. The measures adopted include: thorough rinsing and subsequent conditioning of the P + T parger; elimination of matrix effects by dilution and high salt (not readable); tight specification of purge relevant parameters; split‐inter‐(not readable) to improve GC retention time reproducib

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200103

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

年代:1997

数据来源: WILEY

摘要:

AbstractRetention gape deactivated with Silicone OV‐1701‐OH show good chromatographic performance and remarkable stability against water induced stationary phase degradrdation. In an attempt to better understand the findamentals off the deactivation process using silanol terminated polysiloxanes, a fumed silica was deactivated with Silicon OV‐1701‐OH. In contrast to fused silic capillaries, fumed silica (Aerosil A‐200) can be studied by29Si cross‐polarization magic‐angle‐spinning (CPMAS) NMR, thus serving as a model substrate for fused silica. Retention data from inverse gas chromatography at infinite dilurion and29Si CP MAS NMR data of five Aerosil phases, differing in residual silanol surface concentration, are correlated with the aim of validating this approach for stationary phase characterization. A comparatively detailed model of the deactivating polymer layer that explains the observed absorption activities is deduced.Surface silanols are shown to play a key role in the polymer layer, the structure of which is of primary importance for the absorption behavior after deactivation. Contrary to common belief, the absolute silanol surface concentration after deativation is only of secondary importance for the overall absorption activity. High silanol surface concentrations enhance degradation of the polysiloxane chains into small cyclic fragments as well as subsequent absorption and immobolization to the silica substrate surface. The mobility of linear polysiloxane chains in the kHz regime (as determined bby NMR cross‐polarization dynamics) appears to determine the extent which the residual silanols are accessible for analytes. It is therefore anticipated that there is an optimum silanol surface concentration of fused silica surfaces to be deactivated with silanol terminated polysiloxanes; it should be lazrge enough to adsord polymer fragments, but not large to avoid excessive residual

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200104

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe paper describes a capillary GC/MS hardware arrangement allowong either:(a)on‐line injection of sample of gases and vapors coming from dynamic headspace or purg&trap samplers and their subsequent cryofocusing/thermal desorption prior to the analytical capillary column (first column):(b)direct injection of liquid samples through a cold on‐column injector into a second analytical column (counted in series with the first).Chromatographic profiles of acacia honey aromas provide condirmation of the suitability of this sys

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200105

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe behavior of bovine whey proteins in Reversed‐Phase High Performance Liquid Chromatography (RP‐HPLC) systems has been investigated. The Linear Solvent Strength (LSS) model has been applied to the separation of these proteins studying how their retention time and band broadening change when different gradient parameters are modified. From our results it is deduced that the LSS model describes the behaviour of the whey proteins in RP‐HPLC. Also, it seems that ts(the retention time for non‐retained solutes) depends on the size of these proteins. The good fit observed between experimental data and the equations deduced from the LSS model allows the prediction of a gradient shape that permits a rapid analysis of the above mentioned p

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200106

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

年代:1997

数据来源: WILEY

摘要:

AbstractRecent methods employed for the analysis of algal toxins have focused on high performance liquid chromatography. However these methods suffer from poor resolution, poor efficiency, and long analysis times. This study involves the investigation of a number of toxins including nodularin, microcystin LR, YR, and RR which are cyclic peptides produced by strains of blue‐green algae. The electroseparation mode was micellar electrokinetic capillary chromatography (MECC) using a borate buffer containing sodium dodecyl sulfate (SDS) as the surgactant of choice. The method was optimized with standard toxin compounds and employed for the screening opf toxins in supercritical fluid extracts (SFE) of freeze‐thawed algal scum samp

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200107

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

年代:1997

数据来源: WILEY

摘要:

AbstractFour new stationary phases for HPLC were prepared by modifying silica gel with a trifrnctional aminoalkyl silane. A conjugated π‐electron system was linked to the amino group either directly or with a carboxylic anhydride as a spacer in between. Characterization and dynamic measurements of the new stationary phases were performed by solid state NMR spectroscopy. The results of the29si and13C CP/MAS techniques were compared with the recently developed1H MAS‐only technique. Despite strong homonuclear dipole‐dipole interactions it was possible to obtain well resolved1H MAS spectra of those stationaru phases with a high degree of crosslinking. Limited mobility of the aromatic ligand fragments is common for all examined stationaryu phases.The chromatographic properties of the new phases were tested by their ability tio sepatate a mixture of eight PAHS. It could be shown that the π‐π interaction mechanism is responsible for the separation of the eight PAHs, because the elution order of the PAHs did not changem despite the use of both a nonpolar mobile phase (n‐heptane) and a polar mobile phase (methanol/ wa

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200108

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

年代:1997

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200109

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

年代:1997

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200110

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

年代:1997

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240200111

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

年代:1997

数据来源: WILEY