bluuebunny/crossref_metadata_2025_split huggingface dataset:
LC‐amperometric determination of tert‐butylcatechol in N‐methyl‐2‐pyrrolidone stream containing polar and nonpolar impurities
Authors: Barman Bhajendra N. 
Published: May 2005

AbstractAmperometric detection is shown to be highly selective and sensitive for the determination of tert‐butylcatechol (TBC) added as an antioxidant in the circulating N‐methyl‐2‐pyrrolidone (NMP) used for the purification of 1,3‐butadiene by extractive distillation. The separation of TBC from numerous polar and nonpolar species present in the analyte is achieved on a 5‐cm reversed‐phase C‐18 column using acetonitrile‐water gradient conditions, both solvent components containing tetrabutyl ammonium dihydrogen phosphate as the amphiphilic modifier. The separation process is optimized for the resolution of TBC from nonpolar hydrocarbons as well as polar compounds, and a complete elution of all species from the column. An applied potential of 0.6 V relative to the Ag/AgCI electrode is found to provide an optimum sensitivity by the amperometric detector. It is also shown that the hydrocarbon content in NMP can be monitored simultaneously by coupling a spectrophotometric detector in series.
The analysis of chlorinated dibenzofurans in municipal fly ash: Supercritical fluid extraction vs Soxhlet
Authors: Onuska Francis I. , Terry Ken A. , Wilkinson R. J. 
Published: May 2005

AbstractA multiresidue supercritical fluid extraction procedure for chlorinated dibenzofurans (PCDFs) has been optimized as an efficient method for the determination of these compounds in fly ash samples. The results were compared with those obtained by Soxhlet extraction. Extracts from the two procedures were analyzed by gas chromatography–mass spectrometry (HRGC–MS) Statistical analysis of the results confirmed that supercritical fluid extraction provides data with a relative standard deviation of less than 10% while Soxhlet extraction data show a much greater spread.
Determination of pentane in human breath by gas chromatography
Authors: Moodie Ian M. , Labadarios Demetre 
Published: May 2005

AbstractA new procedure, requiring expired sample volumes of approximately 2L, has been developed for the quantitative determination of n‐pentane in human breath. The methodology capitalizes on the superior resolving power and separating efficiency of the open tubular capillary column and incorporates an effective prechromatographic cryofocusing technique. Molecular sieve is used to simultaneously remove moisture and carbon dioxide from breath samples which are “spiked” with an internal standard to optimize the validity of analysis. Reproducible data for both internal standard spiking (CV = 5.8%) and sample n‐pentane level (CV = 3.2%) have been obtained, together with a mean recovery of 104%. Preliminary data show n‐pentane levels in normal female subjects (n = 10) to range from 0.62 to 3.16 nmole/L (mean 1.76 nmole/L) and in males (n = 10) from 3.20 to 8.76 nmole/L (mean 5.66 nmole/L).
Capillary supercritical fluid chromatography of limonoids
Authors: Raynor Mark W. , Roberts Sianne L. , Mulholland Dulcie A. 
Published: May 2005

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 of Aphanamixis polystacha (Meliaceae) and the stem bark of Harpephyllum 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 of Entandrophragma delevoyii (Meliaceae). One limonoid and two protolimonoids isolated from the extract were separated by SFC.
On‐line high performance liquid chromatography — multidimensional gas chromatography and its application to the determination of stilbene hormones in corned beef
Authors: Chappell Colin G. , Creaser Colin S. , Shepherd Martin J. 
Published: May 2005

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 described.
Analysis of free and esterified sterols in vegetable oil methyl esters by capillary GC
Authors: Plank Christina , Lorbeer Eberhard 
Published: May 2005

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 with N,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 sample.
Investigation into the GC separation of enantiomers on a trifluoroacetylated cyclodextrin. Part II: Effect of derivatization on stereoselectivity towards alcohols
Authors: Smith Ian D. , Simpson Colin F. 
Published: May 2005

AbstractTwo acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6‐di‐O‐n‐pentyl‐3‐O‐trifluoroacetyl)‐ γ‐cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2‐ and 3‐hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four‐carbon chain attached to the stereogenic center. For longer‐chain fluoroacyl derivative groups stereoselectivity was higher for the 2‐ and 3‐hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl‐branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole–dipole contribution and some form of steric component, depending upon the shape and/or size of the solute.
Purification and analysis of partially alkylated cyclodextrins by liquid and gas chromatography
Authors: Deege Alfred , Husmann Heribert , Hübinger Eduard , Kobor Frank , Schomburg Gerhard 
Published: May 2005

AbstractComplex mixtures of partially alkylated cyclodextrins can be analyzed by both HPLC and high temperature capillary GC. Because of the limited efficiency of LC, suitable analytical and preparative separations can be achieved only with systems of carefully optimized selectivity. Using LC it has been possible to isolate and purify single cyclodextrin species from very complex mixtures of components which contain unreacted hydroxyl groups in addition to the alkoxy groups. Analysis of the reaction mixtures and of fractions taken from LC separations can be performed with advantage by high resolution capillary GC at high temperatures between 300 and 400 °C. The thermal stability of partially alkylated cyclodextrins in high temperature GC is considerably increased by trimethylsilylation of the free hydroxyl groups. Fast atom bombardment mass spectrometry and proton NMR were used to identify species isolated from the preparative LC separations.
MDGC–MS: A powerful tool for enantioselective flavor analysis
Authors: Full Gerhard , Winterhalter Peter , Schmidt Gertraut , Herion Peter , Schreier Peter 
Published: May 2005

AbstractThis paper reports the differentiation between the enantiomers of theaspiranes and theaspirones, potent flavor compounds widely used in the flavor industry. Optically pure reference compounds of isomeric theaspiranes were obtained by enantioselective synthesis. Enantiomerically pure reference theaspirones were isolated from quince fruit; their absolute stereochemistry was assigned by CD spectroscopy. For both types of compounds the order of elution was elucidated by using authentic reference compounds. These data enabled the determination of the enantiomeric distribution of both types of compounds in a variety of plant tissues.Because of the complexity of the natural flavor isolates, compounds were identified by mass spectrometry after multidimensional gas chromatography employing a Sichromat 2 double oven chromatograph. After separation of the target compounds on the first, achiral, column (DB‐5), they were transferred to a chiral column (C‐Dex B) for determination of the enantiomeric distribution. Multiple ion detection (MID) enabled the determination of the enantiomeric distribution even for complex mixtures containing the target compounds at extremely low levels.
Analysis of organic compounds in environmental samples by headspace solid phase microextraction
Authors: Zhang Zhouyao , Pawliszyn Janusz 
Published: May 2005

AbstractThe analysis of samples contaminated by organic compounds is an important aspect of environmental monitoring. Because of the complex nature of these samples, isolating target organic compounds from their matrices is a major challenge. A new isolation technique, solid phase microextraction, or SPME, has recently been developed in our laboratory. This technique combines the extraction and concentration processes into one step; a fused silica fiber coated with a polymer is used to extract analytes and transfer them into a GC injector for thermal desorption and analysis. It is simple, rapid, inexpensive, completely solvent‐free, and easily automated. To minimize matrix interferences in environmental samples, SPME can be used to extract analytes from the headspace above the sample. The combination of headspace sampling with SPME separates volatile and semi‐volatile analytes from non‐volatile compounds, thus greatly reducing the interferences from non‐target compounds.This paper reports the use of headspace SPME to isolate volatile organic compounds from various matrices such as water, sand, clay, and sludge. By use of the technique, benzene, toluene, ethyl‐benzene, and xylene isomers (commonly known as BTEX), and volatile chlorinated compounds can be efficiently isolated from various matrices with good precision and low limits of detection. This study has found that the sensitivity of the method can be greatly improved by the addition of salt to water samples, water to soil samples, or by heating. Headspace SPME can also be used to sample semi‐volatile compounds, such as PAHs, from complex matrices.
Deactivation of precolumns for capillary GC by a thin layer of OV‐1701
Authors: van der Hoff G. René , van Zoonen Piet , Grob Konrad 
Published: May 2005

AbstractDeactivation of precolumns with an ultra thin film of OV‐1701 provided inertness at least equal to silylation, but better resistance to water. Dynamic coating of the raw fused silica capillary is, furthermore, much faster than the hydrothermal treatment/silylation procedure.
Carbon dioxide versus xenon as a mobile phase for flow cell packed column SFC/FT‐IR
Authors: Kirschner Cynthia Hume , Taylor Larry T. 
Published: May 2005

AbstractXenon is compared to carbon dioxide as a mobile phase for super critical fluid chromatography/Fourier transform infrared spectrometry. The study showed xenon to be comparable to carbon dioxide in terms of resulting chromatography for non‐polar analytes. Xenon was confirmed to be a very poor mobile phase, however, for polar analytes. It was determined that small wavenumber shifts in the infrared spectra of probe analytes occurred as either the density or temperature of the mobile phase was increased. The degree of these shifts was often similar for xenon and carbon dioxide. Analyte spectra for five different compounds were produced in both super critical xenon and carbon dioxide and compared to condensed phase and vapor phase library spectra. In all cases, carbon dioxide spectra were readily matched to their corresponding vapor phase spectra, despite having blanked portions of the spectrum due to carbon dioxide infrared absorption. Xenon produced technically superior spectra without such blanked regions, but at a much higher economical cost than carbon dioxide and with no real improvement in terms of library matching.
Enantioselective separations by capillary GC on derivatized cyclodextrins. Part 2: Determination of enantiomeric excess of some racemic 2,3‐isopropylidene‐1,2,3‐cyclohexanetriol derivatives on permethyl α‐, β‐, and γ‐cyclodextrins
Authors: Jaques K. , Buda W. , Dumortier L. , Van der Eycken J. , Venema Arnold , Sandra Pat 
Published: May 2005

AbstractCapillary GC on permethyl α‐, β‐, and γ‐cyclodextrins has been applied to separate and quantify the enantiomers of some 2,3‐iso‐propylidene‐1,2,3‐cyclohexanetriol derivatives. Quantitative CGC data are compared to those obtained with chiral shift 1H NMR.
Applications of capillary supercritical fluid chromatography to the characterization of edible oils and traditional chinese medicines
Authors: Shen Yufeng , Huang Hongxin , Liu Xueliang , Wang Qinghai , Zhou Liangmo 
Published: May 2005

AbstractA home‐made supercritical fluid chromatograph fitted with a capillary micropacked column and equipped with FID detection has been used to separate the components of silicone DC‐200, beeswax, tea oil, cod‐liver oil, rancid butter, and several traditional Chinese medicines such as Honghua oil, Jiuxin oil, and Wanhua oil.
Microcolumn liquid chromatography with thermionic detection of the enantiomers of O‐ethyl S‐2‐diisopropylaminoethyl methylphosphonothioate (VX)
Authors: Kientz Charles E. , Langenberg Jan P. , Th. Brinkman Udo A. 
Published: May 2005

AbstractAn improved interface for the on‐line coupling of microcolumn liquid chromatography (micro‐LC) with thermionic detection (TID) is described. Modifications have been made to enable separate adjustment of the eluent introduction and the detector flame temperature in order to improve the sensitivity and ease of use of the system.The micro‐LC‐TID was used for the chiral separation of the nerve agent O‐ethyl S‐2‐diisopropylaminoethyl methylphosphonothioate (VX). Baseline separation for the enantiomers of VX was obtained on Chiralcel OD using 1% isopropanol in hexane as the eluent. The detection limit of VX using 60 nl injections is ca. 5 μg/ml (ppm range). However, when using large‐volume injections (10 μl) the detection limit is ca. 25 ng/ml (ppb range).
Instrument‐induced effects in the analysis of polycyclic aromatic compounds by capillary gas chromatography with atomic emission detection (GC‐AED)
Authors: Janák Karel , Östman Conny , Carlsson Håkan , Bemgård Agneta , Colmsjö Anders 
Published: May 2005

AbstractPeak splitting of high molecular weight polycyclic aromatic compounds originating from the microwave plasma of an atomic emission detector (AED) coupled to a GC has been described and evaluated. The influence of the solute structure, solute concentration, and physical conditions in the AED (such as detector temperature, make‐up gas flow, concentration of reagent gases and distance of column end from the plasma) have been studied. An explanation is presented for peak splitting, which is based on an insufficient solute decomposition and solute mass flow in the discharge tube. Modification of the instrument by introduction of additional make‐up gas applied through the transfer line has been shown to improve peak shape and solute response.
Fossil fuel applications of SFC and SFE: A review
Authors: Levy Joseph M. 
Published: May 2005

AbstractThe use of supercritical fluid technology for sample preparation and analysis in the petroleum industry will be described using various examples including: separation of petroleum fuels into hydrocarbon classes, determination of polynuclear aromatic hydrocarbon in soils and petroleum fuels, characterization of fuel‐contaminated soil, assessment of fuel boiling point distribution, determination of polymer additives, and characterization of shale rock and drilling mud.
Application of high temperature high resolution gas chromatography to paraffinic deposits in petroleum production pipelines
Authors: de Aquino Neto Francisco Radler , Cardoso Jari Nobrega , dos Santos Pereira Alberto , Fernandes Maria Conceiçao Zupo , Caetano Carlos Alberto , de Castro Machado Andre Luiz 
Published: May 2005

AbstractHTHRGC was found essential for optimizing representative preparation of high molecular weight samples and enabling fingerprinting of heavy fractions of crude oils and associated paraffinic deposits in production pipelines. Laboratory experiments aimed at simulating the process of paraffin deposition could also be easily evaluated. A comparative investigation of the performance of cold on‐column and SPI (PTV type) injectors, in conjunction with high temperature capillary columns, for analysis of high molecular weight fractions, was also conducted during the course of this work.
Identification of the constituents of a complex mixture by combined use of retention indices and specific multidetection responses
Authors: Bicchi Carlo , D'Amato Angela , Orlandin Massimo 
Published: May 2005

AbstractThe ratio of the responses of two different specific detectors to a single compound has, when used in conjunction with the compound's retention index, been investigated as an identification criterion for the compound. The ECD:NPD and ECD:FPD response ratios have been used for the identification of some pesticides. Analyses were performed with a single column – dual parallel detection – personal computer system.The reliability of the detector response ratio (DRR) was demonstrated by the consistency of detector response with time, and the influence of the quantity of analyte and of the chromatographic operating conditions. These factors were selected in the expectation that the technique could be used for routine trace analysis.
Analysis of a C9C10 aromatic hydrocarbon pyrolysis distillate by multidimensional capillary GC and multidimensional capillary GC‐MS
Authors: Henderickx Huub J. W. , Ramaekers Jan J. M. 
Published: May 2005

AbstractThis paper describes the use of multidimensional capillary gas chromatography for analysis of individual components in a C9C10 aromatic hydrocarbon pyrolysis distillate containing substantial amounts of aromatic olefins. By coupling this GC‐GC system on‐line to a mass spectrometer difficulties in identifying overlapping compounds were overcome. No coelution of different types of compound was observed, but a few isomeric compounds such as methylstyrenes were poorly separated.
Effect of alkali metals and metal‐ammonia complexes on electroosmosis, effective field strength, and resolution in the separation of diuretics by CZE
Authors: Jumppanen Juho H. , Sirén Heli , Riekkola Marja‐Liisa 
Published: May 2005

AbstractThe counter ion in CZE separation systems affects resolution, effective field strength and electroosmosis. Alkali metals (lithium, sodium, potassium, and cesium), the ammonium ion, and several complexes of metals with ammonia ([Ag(NH3)2]+, [Cu(NH3)4]2+, [Zn(NH3)4]2+, [Cd(NH3)4]2+, [Ni(NH3)6]2+, and [Co(NH3)6]2+) have been studied for their effect on the separation of diuretics. With the alkali metals the electroosmotic flow velocity decreased and the effective field strength and resolution increased as the hydrated radius of the alkali metal decreased.All the metal‐ammonia complexes except that with silver greatly reduced the electroosmotic flow velocity (Veo) and had only a slight effect on the effective field strength (Eeff). Because these complexes had a negligible effect on the ionic strength of the buffer, they enabled high separating power to be maintained during the separation, and hence the use of more energy in the separation system. This yielded better resolution of the compounds, but the analysis time was then compromised.A simultaneous reduction in capillary length and Veo while maintaining the high voltage enabled increased resolution without an increase in analysis time. The ability to control Veo by adding small concentrations (< 100 μM) of metal complexes to the buffer solution makes it possible to adjust the analysis time and capillary length independently while employing high separation power.
Computerized GC/MS detection of monoaromatic and triaromatic steroid hydrocarbons in Alamein crude oil
Authors: Barakat Assem O. 
Published: May 2005

AbstractSeries of C‐ring monoaromatic steroid hydrocarbons (C21, C22, C27  C29) and triaromatic steroid hydrocarbons (C20, C21, C26  C28) have been recognized in the aromatic hydrocarbon fraction of Alamein crude oil from the western desert, Egypt. Detection of these compounds were based on mass fragmentography of the key ions m/z 253 and m/z 231 and comparison of the mass spectra and relative retention times with literature data. The predominance of the C29 monoaromatic steroids and C28 triaromatic steroids provide further evidence for a land plant origin of Alamein oil. The results substantiate previous evidence of the occurrence of an aromatization process with increasing maturation and indicate a moderate maturity level for Alamein oil.
Chiral stationary phase design: A study in optimization
Authors: Pirkle William H. , Bowen William E. 
Published: May 2005

AbstractA π‐basic, brush‐type chiral stationary phase (CSP) derived from (S)‐N‐(1‐naphthyl)leucine undecenyl ester has been shown to effectively separate the enantiomers of a broad array of π‐acidic analytes. Armed with a mechanistic hypothesis as to how this CSP differentiates between the enantiomers of π‐acidic derivatives of α‐amino acids, the structure of this CSP was modified in a series of steps, each intended to enhance the enantioselectivity of the CSP. Specifically, brush‐type CSPs were prepared from N‐(5‐naphthyl)leucine di‐n‐propyl amide and from N‐(5‐acenaphthyl)leucine di‐n‐propyl amide. The latter selector was also incorporated into a polysiloxane, then coated and bonded to silica. The rationale for each of the structural changes, and its effect on the enantioselectivity of the resulting CSP is described.