摘要:

AbstractSolvent‐assisted supercritical fluid extraction is superior to Soxhlet extraction, solvent extraction at reflux, and simultaneous setam distillation solvent extraction for the isolation of semivolatile compounds from the cinnamons of commerce. Optimized extraction conditions are described using carbon dioxide at 300 atm and 70°C to extract 0.5 g of powdered cinnamon mixed with 4.5 g of anhydrous sodium sulfate to which 1.0 ml of acetonitrile was added at the start of the sequential 30 min static and 30 min dynamic extraction. The semivolatile compounds were collected by solvent trapping in ethyl acetate and analyzed directly by series coupled‐column gas chromatography after filtration and partial solvent evaporation. Twenty‐one compounds identified by mass spectrometry were quantified in twenty‐four samples of cinnamon and cassia purchased in Sri Lanka, Korea, United Kingdom, and the United States of America. True cinnamon is easily distinguished from cassia by the presence of eugenol, absence of δ‐cadinene, much lower amounts of coumarin, and larger amounts of benzyl benzoate. Principal component analysis using the relative composition of the twelve major semivolatile compounds provides a clear distinction between true cinnamon and cassia as well as useful interspecies differences which can be used for further cla

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180802

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

年代:1995

数据来源: WILEY

摘要:

AbstractSupercritical fluid extraction was coupled directly with high performance liquid chromatograph. The system was evaluated for direct injection of supercritical CO2and modified supercritical CO2at high pressure and temperature onto a HPLC system with varying mobile phase compositions and flow rates. Injection of 9 μL supercritical CO2onto the HPLC using methanol/water mobile phases from 100% methanol to 80% with a flow of 1.0 mL/min did not adversely affect the baseline of UV detector. However at higher percentages of water, CO2solubility in the mobile phase decreased and caused baseline interferences on the UV detector. At higher HPLC mobile phase flow rates, supercritical CO2was injected to higher percentages of water without any effect on the UV baseline. Also, increasing the extraction pressure or modifier concentration did not change the results. Separations of polynuclear aromatic hydrocarbons and linear alkenebenzene sulfonate test mixtures were obtained using on‐line SFE/HPLC interfaced syst

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180803

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe retention behavior of polycyclic aromatic hydrocarbons (PAHs) in packed‐column supercritical fluid chromatography (SFC) is studied for monomeric and polymeric C18columns. Molecular shape discrimination (shape selectivity) is assessed through the use of Standard Reference Materials (SRMs), adn changes in selectivity are studied as a function of temperature, pressure, and mobile phase composition. Examples of separations of complex PAH isomer mixtures are presented, and guidelines are provided for modification and optimization of shape selectivity in SF

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180804

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe possibility of using supercritical‐fluid chromatographic retention data for examining the effects of operational parameters, such as pressure and flow rate, on the extraction characteristics in supercritical‐fluid extraction (SFE) was investigated. A model was derived for calculating the extraction efficiency in SFE from retention data and peak shapes measured in supercritical‐fluid chromatography (SFC). By performing the SFC experiments at the same pressure and temperature as the SFE extractions using the SFE extraction cell as the SFC column, an accurate prediction of extraction efficiencies could be made. Finally, the effects of matrix composition and analyte concentration on extraction efficiency were st

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180805

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

年代:1995

数据来源: WILEY

摘要:

AbstractHydroxylated polychlorobiphenyls (polyhydroxy‐PCBs) are subjected to severe discrimination effect when they are introduced into a capillary gas chromatograph by splitless injection. This effect can be considerably reduced by using a pulsed pressure injection to favor sample transfer and by further programming the eluent gas pressure during the GC run. By multistep gas pressure programming, splitless injection provides analytical performances and chromatograms for (poly)hydroxy‐PCBs closely resembling those obtained by on‐column injection, whose use is generally discouraged with real environmental samples. Among the six model compounds studies, the dihydroxy congeners exhibit the best re

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180806

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

年代:1995

数据来源: WILEY

摘要:

AbstractThe application of SPME, a solventless extraction procedure, is demonstrated for two environmental applications. Extraction of VOCs by SPME is coupled with analysis on short narrow bore capillary gas chromatography columns. The technique is shown both as a fast screening tool and as part of an analytical procedure when combined with a mass spectrometer. Data show the linear range of the procedure. The extraction of chlorinated pesticides from hazardous wastewater and drinking water by SPME is also described in this paper. SPME is compared to traditional extraction procedures with respect to cost, time, ease of use, solvent usage, and sample usage.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180807

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

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180808

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

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180809

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

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180810

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

年代:1995

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240180811

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

年代:1995

数据来源: WILEY