bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extending the scope of enantiomer separation by capillary supercritical fluid chromatography on immobilized polysiloxane‐anchored permethyl‐β‐cyclodextrin (Chirasil‐Dex)
Authors: Jung Martin , Schurig Volker 
Published: May 2005

AbstractImmobilized polysiloxane‐anchored permethyl‐β‐cyclodextrin (Chirasil‐Dex) with a cyclodextrin content of approximately 30 % by weight, previously employed as a versatile chiral stationary phase for the separation of enantiomers by GC, has been used for the separation of enantiomers by capillary supercritical fluid chromatography (SFC). A considerable number of racemates could be resolved, e.g. aromatic alcohols, amino alcohols (TFA derivatives), and underivatized acids. Many pharmaceutical compounds were among those analyzed, including several NSAIDs (e.g. ibuprofen and ketoprofen), a steroidal drug (nor‐gestrel), a barbiturate (hexobarbital), and others.Among the racemates resolved were many which cannot be analyzed by GC owing to low volatility or decomposition at elevated temperatures. For two racemates, analysis temperature and mobile phase density were systematically varied to give constant analysis times or capacity factors k. Low temperatures (ca 60 °C) yielded the best separation in term of separation factor, α, or resolution, Rs, even though higher densities had to be used. In comparison with GC, capillary SFC was able to furnish higher separation factors and similar resolution. The applicability of capillary SFC for the analysis of mixtures of cyclodextrin derivatives, e.g. those used in the synthesis of Chirasil‐Dex, was, furthermore, demonstrated.
Evaluation of flow restrictors for open‐tubular supercritical fluid chromatography at pressures up to 560 atm
Authors: Pinkston J. David , Hentschel Rosemary T. 
Published: May 2005

AbstractProper performance of the flow restrictor is of crucial importance in supercritical fluid chromatography. This is especially the case when the restrictor is the interface between the chromatographic column and a detector operating at lower pressure than the column. The performance of three types of fixed flow restrictor, the “tapered”, the “integral”, and the “frit”, was examined. The test mixtures chosen covered a range of polarities and molecular weights. Polydimethylsiloxane with an average molecular weight of 10,000 was used as a low polarity probe. Two polyethylene glycol mixtures were chosen as higher polarity probes. One consisted of a mixture of polyethylene glycol standards with average molecular weights ranging from 200 to 1450. The other polyethylene glycol mixture had an average molecular weight of 2000. The polydimethylsiloxane standard did not elute when the frit restrictor was used. Satisfactory results were obtained when the tapered and integral restrictors were employed. All three restrictors provided satisfactory results for polyethylene glycol oligomers eluting up to approximately 40.5 MPa (400 atm). However, for oligomers eluting above this pressure, the peaks merged into a broad hump with the frit restrictor, while the tapered and integral restrictors provided satisfactory separations. The integral restrictor produced more evenly spaced, more well resolved peaks at the high‐pressure end of the chromatograms than did the tapered restrictor. This is shown to be due to differences in the rates of increase in mobile‐phase velocity with increasing pressure for the two restrictors.
Indirect conductimetric detection of cyclodextrins in liquid chromatography
Authors: Takeuchi Toyohide , Miwa Tomoo , Hemmi Akihide , Maeda Tsuneaki 
Published: May 2005

AbstractIndirect conductimetric detection of cyclodextrins (CDs) was investigated in liquid chromatography (LC). The mobile phase contained an electrolytic substance which maintained high background, and CDs were indirectly detected owing to a depression of the background signal due to dilution of the mobile phase by the analyte molecules. The dynamic reserve, defined as the ratio of the background to its noise level, was (1–2) × 105, and the detection limits at S/N = 3 were 23–40 ng for CDs when a microcolumn LC system was employed.
HRGC and GC–MS analysis of essential oil from colombian ylang‐ylang (Cananga odorata Hook fil. et Thomson, forma genuina)
Authors: Stashenko Elena , Martinez Jairo René , MacKu Carlos , Shibamoto Takayuki 
Published: May 2005

AbstractSamples of essential oil from Colombian ylang‐ylang trees were analyzed by means of HRGC, HRGC–MS, IR and 1H‐ and 13C‐NMR. 57 components were detected, 51 of which were positively identified. Camphene and anethol were identified in ylang‐ylang essential oil for the first time. Among the composition‐determining variables studied (extraction time, part of the flower, and flower freshness), the extraction time and the flower condition (fresh versus dry) were found to have the largest incidence in the quality of the essential oil.
On‐line liquid backflush—a new technique for GC analysis of samples containing nonvolatile material
Authors: Hagman Gunnar , Roeraade Johan 
Published: May 2005

AbstractDeteriorated performance in capillary GC is often caused by the deposition of nonvolatile components in capillary GC inlets. In many cases this is a limiting factor in trace analysis of complex samples. Volatile solutes of the sample interact with the high boiling material, which leads to broadened and unsymmetrical peaks. This paper describes a novel technique which utilizes independent temperature programs of a retention gap and the column as well as a liquid backflush of the retention gap. Samples that normally contaminate the retention gap after a few injections can be repeatedly injected over extended periods of time, while the chromatographic resolution is retained.
Procedure for testing inertness of inserts and insert packing materials for GC injectors
Authors: Grob Konrad , Wagner Christoph 
Published: May 2005

AbstractThe inertness of injector inserts and insert packing materials, such as glass or fused silica wool, is tested by a procedure based on split injection and rapid isothermal chromatography. Resulting sharp peaks sensitively reveal peak deformation resulting from adsorptivity, acid/base interaction, and excessive retention power. Degradation of labile components is detected by loss of material and degradation products. Adsorptivity was no problem on injecting 300 ng amounts. Degradation only occurred for raw wools; however, the retention power of some wools seemed unnecessarily high. On injection of smaller quantities, degradation remained similar, but adsorptivity increased significantly.
Construction of an all‐glass/fused silica, zero dead volume multidimensional gas chromatographic system using press‐fit connectors: Preliminary results
Authors: Ibáñez Carlos 
Published: May 2005

AbstractA multidimensional gas chromatographic system has been constructed using commercially available press‐fit connectors, glass splitters, and fused silica lines. In this new design all the lines are continuously purged with carrier gas, ensuring no dead volumes in the chromatographic path. Some preliminary results and practical considerations are presented.
Analysis of volatiles associated with industrial scale processing of expanded polystyrene. Part I: Methods development
Authors: Hathcock Stanley L. , Bertsch Wolfgang 
Published: May 2005

AbstractThis paper reports on the methodology to collect volatiles from the hot‐wire cutting of expanded polystyrene. Analytical scale pyrolysis was used to model the conditions in the field. It appears that gas chromatographic profiles are little affected by the presence or absence of flame retardants. Pyrolysis in air or in an inert gas generates very similar pyrograms but the temperature at which pyrolysis takes place is the major factor affecting amount and distribution of volatiles. An experimental design is discussed that permits to model in the laboratory the production of volatiles generated in the field.
Capillary gas chromatography of the terpene components of Picea abies K.
Authors: Boscherini Giovanna , Michelozzi Marco 
Published: May 2005

AbstractThe terpene composition of cortical tissue in five Italian populations of Picea abies K. has been analyzed by headspace gas chromatography. The results of analysis of variance showed significant differences in content of most terpenes between the populations. Because intensive sampling is required for description of the natural variability of forest trees, the application of headspace gas chromatography may provide many opportunities in genetic research.
Electrochemical detection for trace analysis by capillary HPLC
Authors: Ruban Vladimir F. 
Published: May 2005

AbstractAn amperometric‐type electrochemical detector is proposed for use in capillary HPLC. Its cell (volume 60 nl) contains a cylindrical working electrode for detecting the presence of electroactive compounds. The noise level is 3–5 pA depending on the potential. The minimum detectable concentrations of the o‐, m‐, and p‐ isomers of nitrophenol (after separation of a 20 μl sample on a fused silica column) lies between 4 and 18 ng/l. The relative standard deviation of the height of the chromatographic peaks of phenols present at concentrations of 10 ppb does not exceed 0. 08 (n = 5).
Micellar electrokinetic capillary chromatography of nucleic acid constituents and dinucleoside monophosphate photoproducts
Authors: Ramsey Roswitha S. , Kerchner Geoff A. , Cadet Jean 
Published: May 2005

AbstractMicellar electrokinetic capillary chromatography has been explored as an efficient and rapid method of separating the photoproducts of 2′‐deoxyuridylyl‐(3′‐5′)‐thymidine (i.e., cis‐syn and trans‐syn cyclobutane dimers, (6–4) photoproduct, and the related Dewar valence isomer) from normal nucleosides and nucleotides. Three cationic surfactants, dodecyl‐, tetradecyl‐, and hexadecyltrimethy‐lammonium bromide were evaluated and the separations compared with those obtainable with the anionic surfactant, sodium dodecylsulfate. Optimum resolution of the dinucleoside monophosphate photoproducts was obtained using tetradecyltrimethylammonium bromide. By use of this detergent the photoproducts could also be separated from other normal constituents in less than 6 min at −25 kV. Dodecyl‐ and hexadecyltrimethylammonium bromide provided some separation between the various species but sodium dodecylsulfate did not separate the UV radiation‐induced products from either the parent compound or other dinucleoside monophosphates. Increased interaction between negatively charged solutes and positively charged micelles accounts for the differences.
Chemical characterization of gorse pyrolytic oils by capillary gas chromatography
Authors: Bódalo Antonio , León Gerardo , Asanza María Luisa , Gómez Elisa , Guzmán María Amelia 
Published: May 2005

AbstractThermochemical conversion of biomass produces solid charcoal, gaseous fuels, and condensable oils. Because these oils vary widely in composition depending on the cellulosic feedstock and the operating conditions used, analysis of the oils is necessary in order to determine the best ways of utilizing or disposing of them. The major components of the organic oil from pyrolysis of gorse have been characterized by capillary gas chromatography – mass spectrometry. A qualitative study of the aqueous oil from the same source has also been attempted.
The performance of various capillary columns for the analysis of volatile flavor compounds in dairy products by dynamic headspace gas chromatography
Authors: Imhof René , Bosset Jacques O. 
Published: May 2005

AbstractThe aim of this study was to test the suitability and performance of various stationary phases and column dimensions for dynamic headspace gas chromatography of food aromas. The trials were performed using an aqueous test mixture containing thirty seven volatile flavor components of intense aroma, and a sample of ripe Swiss Emmental cheese.The best performance with both samples was obtained with a capillary column coated with a thick film of polydimethylsiloxane. This column resolved the greatest number of compounds in the cheese sample and resulted in the overlapping of one pair of peaks only from the test mixture. Because of its other advantages, i. e. high capacity owing to its film thickness, and insensitivity to the high moisture content of some samples or traces of oxygen in the carrier gas, the polydimethylsiloxane column appears suitable for the analysis of the volatile and highly polar compounds present in complex mixtures such as food aroma.
Separation of fuels, heavy fractions, and crude oils into compound classes: A review
Authors: Lundanes Elsa , Greibrokk Tyge 
Published: May 2005

AbstractPractically all the conventional chromatographic techniques are used in the characterization of the highly complex mixtures of organic compounds occurring in fuels, heavy fractions, and crude oils. This paper surveys the techniques employed for class determination, preparative fractionation of the main classes, and determination of subgroups after class fractionation.
Adsorptive interaction between nitrogen compounds and organic and/or mineral phases in subsurface rocks. Models for compositional fractionation of pyrrolic nitrogen compounds in petroleum during petroleum migration
Authors: Li Maowen , Larter Steve R. , Frolov Yeuge B. , Bjoroy Malvin 
Published: May 2005

AbstractThe results are reported of a range of laboratory chromatographic fractionation experiments with synthetic model compounds and a petroleum pyrrolic nitrogen fraction. Reversed phase separation of pyrrolic nitrogen compounds was governed mainly by the number of carbon atoms in the molecule, with little selectivity toward different positional isomers, whereas normal phase separation of the compounds could be explained in terms of steric effects related to alkylation position. Comparison of experimental results from model compounds with observations made previously using sets of natural samples taken from sedimentary basins clearly suggests adsorptive interactions between organic and mineral phases are involved in the compositional fractionation of pyrrolic nitrogen compounds in petroleum during migration. Detailed studies of the effects of petroleum migration on the molecular distribution of petroleum pyrrolic nitrogen compounds may provide useful, quantifiable, migration‐related geochemical parameters.
Chromatographic characterization of thermally upgraded products from alternative fuels
Authors: Lanças Fernando M. , Vilegas Janete H. Y. , Martins Sérgio , Gobato Elaine A. F. 
Published: May 2005

AbstractAn overview is presented of the analytical approaches developed by our research group over the last ten years for analysis of alternative fuel, both biomass and fossil. The alternative fuels are analyzed successively by PLC‐8 (preparative liquid chromatography–group‐type) fractionation and high resolution gas chromatography. Some of the possibilities for fractionation and characterization of alternative fuels are herein exemplified with sugar cane bagasse pyrolysis products.
Analysis of Fischer‐Tropsch by‐product waters by gas chromatography
Authors: Anderson Richard R. , White Curt M. 
Published: May 2005

AbstractThis paper describes a quantitative technique for the determination of organic constituents in Fischer‐Tropsch by‐product waters. Temperature‐programmed gas chromatography on derivatized bonded polar capillary columns provides the required separation that permits reliable quantitation of individual compounds. A preliminary combined gas chromatographic–mass spectrometric survey to identify the components present in Fischer‐Tropsch by‐product waters is presented. The elution order of 58 identified components is tabulated. Components identified in a typical Fischer‐Tropsch by‐product water include C1–C9 linear and branched alcohols, C3C8 ketones, C2C6 carboxylic acids, and C2C4 linear aldehydes.
Supercritical fluid chromatography of petroleum products using flameless sulfur chemiluminescence detection
Authors: Shearer Randy L. , Skelton Ron J. 
Published: May 2005

AbstractSupercritical fluid chromatography using flameless sulfur chemiluminescence detection has been investigated for the analysis of sulfur compounds in petroleum products. The chromatography and detection system was easy to implement and exhibited good precision, linearity, selectivity, and sensitivity. A minimum detectable limit of 0.3 pg sulfur/s was obtained, and response to sulfur in different sulfur species was nearly equimolar.
Nitrogen speciation of polar petroleum compounds by compound class separation and on‐line liquid chromatography – mass spectrometry (LC‐MS)
Authors: Hsu Chang Samuel , Qian Kuangnan , Robbins Winston K. 
Published: May 2005

AbstractChromatography on Attapulgus clay and on silicic acid has been used to isolate ‘neutral’ and ‘basic’ nitrogen fractions from the 650–1050 °F distillate of an off‐shore Californian crude oil. These polar compounds were subjected to on‐line liquid chromatography – mass spectrometric (LC‐MS) analysis using low voltage electron‐impact ionization high resolution mass spectrometry (LVEI HRMS) and deuterated ammonia chemical ionization (ND3 Cl) to determine the molecules' elemental composition and number of exchangeable hydrogen atoms. On‐line separation of heavy oils into saturated, 1–4 ring aromatic, and polar compounds was performed by normal phase high performance liquid chromatography (HPLC) on a dinitroanilinopropyl (DNAP) silica column.
Enantiomeric composition of the chiral constituents of essential oils. Part 2: Sesquiterpene hydrocarbons
Authors: König Wilfried A. , Rieck Angela , Hardt Ingo , Gehrcke Bärbel , Kubeczka Karl‐Heinz , Muhle Hermann 
Published: May 2005

AbstractA number of sesquiterpene hydrocarbons commonly occurring in essential oils has been prepared as racemic mixtures by chemical synthesis. Preparative gas chromatography with selectively per‐O‐alkylated cyclodextrins has been employed for the isolation of enantiomeric mixtures or pure enantiomers from the essential oils of higher plants and liverworts (Hepaticae). The enantiomers of α‐curcumene, α‐ and β‐bisabolene, β‐elemene, δ‐elemene, α‐copaene, δ‐cadinene, cis‐ and trans‐calamenene, and bicyclogermacrene could be resolved by enantioselective gas chromatography on capillary columns coated with cyclodextrin derivatives. The enantiomeric composition of these sesquiterpene hydrocarbons in various essential oils was determined.
High temperature gas chromatography for the analysis of fossil fuels: A review
Authors: Philp R. Paul 
Published: May 2005

AbstractFor the past two or three decades geochemists have been concerned with the analyses and characterization of compounds, generally hydrocarbons, ranging from C1C40. Significant amounts of information have resulted from these studies which have been extremely useful in many geochemical and environmental studies. However, in the past two or three years the commercial development and availability of high temperature gas chromatography columns has lead to the investigation of the occurrence and distribution of high molecular weight hydrocarbons (HMWHC), and other compounds, in the carbon number range C40C100, present in oils, waxes, bitumens and rock extracts. The ability to study these compounds represents a major advance in organic geochemistry. In some samples these compounds may represent the bulk of the organic components but prior to development of the high temperature columns it was impossible to study their distributions.This paper will review advances that have occurred in terms of the application of high temperature gas chromatography (HTGC) to the analyses of fossil fuel samples and discuss the possible origin and significance of these compounds that have been identified. In addition, some of the potential problems involved in the analyses of these compounds will also be discussed.
Determination of the boiling point distribution of sulfur compounds in light cycle oil using GC with a flame photometric detector and pyrolyzer
Authors: Sung N. J. , Johnson S. J. , Parrott S. L. 
Published: May 2005

AbstractA method has been developed to determine the boiling point distribution of sulfur compounds in light cycle oils (LCO'S). The method chosen for this analysis was GC with a flame photometric detector (FPD) and pyrolyzer. Tests were carried out to evaluate the recovery efficiency, repeatability, and accuracy of the method. Repeatabilities within 2% were obtained. The recovery of benzothiophenes and dibenzothiophenes was close to 100%; this was important because these are the major sulfur components in LCO's. No hydrocarbon or solvent interferences were observed with the use of the pyrolyzer, even for a 95% solvent level. Comparison with results from other techniques showed that the method accurately determined the levels of sulfur compounds in the LCO boiling point range.
Liquid–solid disk extraction followed by supercritical fluid elution and gas chromatography of phenols from water
Authors: Tang Peter Hua‐Tang , Ho James S. 
Published: May 2005

AbstractA method combining the techniques of liquid – solid disk extraction (LSDE) and supercritical fluid elution (SFE) has been developed for the phenols regulated by the Clean Water Act. LSDE uses a disk or membrane made of polytetrafluoroethylene (PTFE) fibrils impregnated with small particles, e.g. styrene divinylbenzene (SDB) resin, to extract phenols from water. After disk extraction the retained analytes are eluted from the disk using SFE. SFE is used as an alternative to liquid solvent elution with an organic solvent. Analytes are separated, identified, and quantified using gas chromatography – ion trap detector mass spectrometry (GC‐ITDMS). The method is capable of sub parts per billion detection limits, and precision of 5–28% RSD. Evaluation of various disks or membranes, such as C18‐silica disks, SDB disks, and ion exchange membranes, has also been performed for the extraction of phenols from water. The results obtained from the in‐situ aqueous acetylation of phenols and extraction of their acetates are quantitative. The utilization of LSDE and SFE techniques has proven to be a more effective approach than liquid – liquid extraction in minimizing air pollution and solvent waste.
Simultaneous enantioselective separation of chlordanes, a nonachlor compound, and o,p′–DDT in environmental samples using tandem capillary columns
Authors: Oehme Michael , Kallenborn Roland , Wiberg Karin , Rappe Christoffer 
Published: May 2005

AbstractTwo capillary columns, one coated with 90 % biscyanopropyl 10 % phenylcyanopropylpolysiloxane (RTx 2330) the other with dimethyl‐t‐butyl‐silylated β‐cyclodextrin dissolved in 85 % methyl 15 % phenyl polysiloxane (PS‐086), have, when employed in tandem, enabled the enantioselective separation of all the chiral chlordanes present in the fish oil reference material SRM 1588, without any overlap between enantiomers of different isomers. This capillary column combination is, furthermore, able to separate the enantiomers of other chiral polychlorinated pesticides such as o,p′–DDT, oxy‐chlordane, a chiral nonachlor, and heptachlor exo‐epoxide. It can be used to determine the enantiomer ratio of these compounds present in the low pg/g range in extracts of marine biota and ambient air.
High temperature gas chromatography of trimethylsilyl derivatives of alcohol ethoxylates and ethoxysulfates
Authors: Rasmussen Henrik T. , Pinto Angela M. , DeMouth Mark W. , Touretzky Pamela , McPherson Bruce P. 
Published: May 2005

AbstractConversion of ethoxylated alcohols to trimethylsilyl derivatives and subsequent high temperature gas chromatography allowed for the determination of alkyl chain distribution, mole average degree of ethoxylation and weight percent distribution of several commercial mixtures. Repetitive derivatizations and analyses of a mixture with a vendor specified mole average degree of ethoxylation of 3.0 (Neodol 23‐3), yielded an experimental result of 2.93 ± 0.05 (n = 6). Mixtures with different alkyl chain distributions and higher degrees of ethoxylation provided similar accuracy. Extension of the method to the analysis of ethoxylated alcohol sulfate raw materials and ethoxylated alcohol sulfates in dishwashing liquids is discussed.