ISSN:0935-6304    

DOI:10.1002/jhrc.1240130102

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

年代:1990

数据来源: WILEY

摘要:

AbstractSynthetic mixtures of additives (antioxidants, UV stabilizers) used in the manufacture of food packaging materials were separated by normal phase HPLC under isocratic or gradient elution, and by capillary SFC using CO2as mobile phase. SFC proved to be more efficient for the separation and determination of additives with a wide range of boiling points and for substances lacking a UV chromophoric moiety. Combined SFC/MS, using a direct coupling interface, produced clear charge transfer spectra resembling EI spectra and proton exchange CI spectra when ammonia was added to the ion source.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130103

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

年代:1990

数据来源: WILEY

摘要:

AbstractHyphenation of packed microcolumn SFC, a photodiode array UV detector, and an inductively coupled plasma spectrometer has been developed in order to evaluate the stability of acetylacetone complexes under supercritical conditions.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130104

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of the column diameter to particle diameter ratio (theKnox‐Parcherratio, designated ϱ) on reduced plate height (h) is examined. The mean diameters of spherical and irregular particles are varied while the column diameter is fixed at 530 μm. For spherical particles a transition in thehversus ϱ plot is observed as in the previous stu

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130105

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

年代:1990

数据来源: WILEY

摘要:

AbstractA chromatograph equipped with one injection valve, two capillary columns with different selectivities, two flame ionization detectors and two electrometers is used to perform simultaneous dual capillary supercritical fluid chromatography. Two sets of retention times and indices are obtained for a mixture of polycyclic aromatic hydrocarbons, from one injection, enabling positive identification. The system is also used to rapidly select a stationary phase for separating hop and beer bittering acids.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130106

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

年代:1990

数据来源: WILEY

摘要:

AbstractSupercritical fluid chromatography (SFC) on a capillary column coated with a smectic mesomorphic crystalline phase is shown to exhibit a typical turnover effect (retentionversuscolumn temperature) for polycyclic aromatic hydrocarbons (PAHs) at lower temperatures than are found on a methylpolysiloxane phase. Liquid chromatography is used to separate various fractions from a coal tar, which are analyzed by high resolution capillary SFC. Different density and temperature programs were investigated to optimize the separations. Simultaneous density and temperature programs gave the best results, and this is thought to be due to increased solute diffusion coefficients which yield highly efficient separations for the high molecular weight polycyclic aromatic hydrocarbons. The separation mechanism is based on the shape of the liquid crystalline phase, solubility, volatility, and molecular geometry of the PAHs.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130107

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

年代:1990

数据来源: WILEY

摘要:

Abstract5 ml air samples from 1.6 l stainless steel canisters were cryogenically preconcentrated before gas chromatographic separation on a thick‐film capillary using a home‐made cryotrap. Quantification in the 10–500 ppt range was carried out with an electron capture detector. Problems during the cryotrap step were caused by carrier gas contamination, water and CO2content of the sample, and a non‐optimal heat desorption rate. Their elimination is described in detail. Compound losses by wall adsorption on stainless steel surfaces were observed when dry gases were used for standard generation. A static multipoint calibration technique using humidified He was developed allowing a precise standard generation down to 100 ppt. The concentration changes in the stainless steel canisters could be neglected over a storage period of at least 1 month as long as a sufficient degree of humidity was present. The overall reproducibility of the quantification and calibration technique is in the order of 1–2% for concentrations between 100–400 ppt when daily recalibrations are

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130108

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

年代:1990

数据来源: WILEY

摘要:

AbstractSeveral commercially available and home‐made reversed phase packing materials packed in capillary columns are evaluated for SFC with pure CO2as mobile phase. Anilines and polycyclic aromatic hydrocarbons are used as test mixture. Some “on column endcapping” experiments are eval

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130109

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

年代:1990

数据来源: WILEY

摘要:

AbstractVariation of the values of free energy of sorption of the methylene unit has been studied in the homologous series ofn‐alkyl methyl ketones,n‐alkyl butyl ketones,n‐alkyl acetates, and methyl esters of carboxylic acids, depending on the homologue number and the temperature of analysis. The experiment was carried out on a capillary column with a thick film of immobilized Silicone SE‐54 and on packed columns with OV‐210 and Silar‐10C. An intramolecular donor‐acceptor interaction between neighboring CH3 and CO groups is assumed to be the reason for anomalously high values of free energy of sorption of the first CH2unit in the series: RmC(O)OCH3, RmC(O)CH3, and RmC(O)C4H9. The anomaly disappeared in stationary phases containing strongly electronegative CF3and CN groups because of specific inter m

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130110

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

年代:1990

数据来源: WILEY

摘要:

AbstractWheat straw lignins obtained by HF, H2SO4, HCL, NaOH, and dioxane/water extraction methods and native wheat straw were subjected to pyrolysis‐gas chromatography (Py‐GC). Pyrolytic fragments were tentatively identified by mass spectrometry using an on‐line Py‐GC‐Lon Trap Detector (Py‐GC‐ITD) and their origin could be attributed to polysaccharides and lignin. Quantitation of fourteen main peaks common to all pyrograms showed statistically significant differences depending on lignin preparation. Pyrograms of typical lignin preparations, native wheat straw, and pure cellulose and ITD mass spectra

ISSN:0935-6304    

DOI:10.1002/jhrc.1240130111

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

年代:1990

数据来源: WILEY