bluuebunny/crossref_metadata_2025_split huggingface dataset:
HRGC separation of hydroperoxides formed during the photosensitized oxidation of (R)—(+)‐Limonene
Authors: Schieberle P. , Maier W. , Firl J. , Grosch W. 
Published: May 2005

Abstract(R)—(+)‐Limonene was photooxidized in the presence of Rose Bengal as catalyst. After TLC isolation, the hydroperoxides formed were separated directly by HRGC and analyzed by MS (El; Cl). Each hydroperoxide isomer was then isolated by HPLC for structure determination which after reduction of the HOO group with sodium borohydride was performed by 1H‐NMR and 13C‐NMR.Six hydroperoxide isomers formed by oxidation of the endocyclic double bond were identified. The compounds eluted from the HRGC column in the following order (proportions are given in brackets) I (40.1%) (1S, 4R)‐p‐mentha‐2, 8‐diene 1‐hydroperoxide; II (5.8%) (1R, 4R)‐p‐mentha‐2, 8‐diene 1‐hydroperoxide; III (20.6%) (2R, 4R)‐p‐mentha‐[1(7), 8]‐diene 2‐hydroperoxide; IV (8.5%) (2R, 4R)‐p‐mentha‐6, 8‐diene 2‐hydroperoxide; V (4%) (2S, 4R)‐p‐mentha‐6, 8‐diene 2‐hydroperoxide; and VI (21.0%) (2S, 4R)‐p‐mentha‐[1(7), 8]‐diene 2‐hydroperoxide. Direct HRGC separation of the limonene hydroperoxides offers, inter alia, the possibility of determining their flavor qualities by HRGC/effluent sniffing.
PoraPLOT Q: A porous layer open tubular column coated with styrene‐divinylbenzene copolymer
Authors: de Zeeuw J. , de Nijs R. C. M. , Buyten J. C. , Peene J. A. , Mohnke M. 
Published: May 2005

AbstractA porous polymer is deposited on the inner wall of fused silica capillary columns. The retention characteristics of this porous polymer were evaluated and found to be comparable with Porapak Q. The porous polymer has a high retention volume which enables the separation of permanent gases at ambient temperatures or higher. The hydrophobic character of the porous polymer allows the injection of water containing samples without changing retention due to adsorption of water. The inertness of the porous polymer allows the elution of a range of apolar and polar compounds. The maximum temperature of the porous polymer was estimated to be 250°C. With this new type of capillary column, high resolution separations are obtained in combination with short analysis times.
Estimation of the instrumental band broadening contribution to the column elution profiles in open tubular capillary liquid chromatography
Authors: Claessens H. A. , Hetem M. J. J. , Leclercq P. A. , Cramers C. A. 
Published: May 2005

AbstractIn comparison with conventionally packed HPLC columns, from a theoretical point of view, open capillary liquid chromatography (OTLC) systems offer a number of advantages like high plate numbers and short analysis times. On the other hand, drastic changes have to be made to the instrumentation. In particular, the contribution to band broadening by the chromatographic equipment must be considerably reduced. In the present study an OTLC system was developed and evaluated, which yields satisfactory results for 26 μm i. d. columns. The determination of the contribution of the chromatographic equipment to the total band broadening is discussed.
OH‐terminated cyanopropyl silicones
Authors: David F. , Sandra P. , Diricks G. 
Published: May 2005

AbstractDue to their high polarity and unique selectivity, cyanopropyl silicones are basic stationary phases for high resolution capillary gas chromatography. Different OH‐terminated cyanopropyl silicones, containing a high cyanopropyl content, were synthesized and chromatographically evaluated. Special attention was paid to the degree of immobilization of the phases in FSOT columns. Depending on the problem at hand, a choice has to be made between immobilization and maximum selectivity.
Simple instrument modification for packed fused silica capillary or micro‐LC: Evaluation on the use of tubular UV‐detection cells
Authors: Vindevogel J. , Schuddinck G. , Dewaele C. , Verzele M. 
Published: May 2005

AbstractMost UV detector modifications for Micro‐LC use tubular fused silica tubes (on‐column UV detection). To get a better understanding of the optical processes involved, a microcomputer model was developed in order to extract design guidelines. A gradient elution test was used for fast cell quality determination.
Gas chromatography and gas chromatography/mass spectrometry for the characterization of complex mixtures of large oligosaccharides
Authors: Karlsson H. , Hansson G. C. 
Published: May 2005

AbstractHigh temperature gas chromatography and gas chromatography/mass spectrometry are used in the characterization of complex natural mixtures of permethylated oligosaccharides released from proteins or lipids. The high resolution allows separation of isomeric compounds and the mass range extends to oligosac‐charides around molecular mass 2000 daltons or 10 sugar residues for isomalto‐oligosaccharides. The mass spectra of permethylated oligosaccharide alditols from mucin glycopeptides are very informative and the approach allows a simple and rapid characterization of these complex components.
Sample enrichment in high speed narrow bore capillary gas chromatography
Authors: van Es A. , Janssen J. , Cramers C. , Rijks J. 
Published: May 2005

AbstractReduction of the column diameter has proved to be a highly efficient tool to increase the speed of analysis. Unfortunately, the requirements for instrumental design with respect to sample input band width, low dead volume interfacing, and time constants of detection and registration systems are the more critical the smaller the inside diameter.Recently we reported input band widths as low as 1 ms [1] for gaseous samples at ppm concentration levels, without any preconcentration, in a study with narrow bore columns and thermal conductivity detection.In this study a simple versatile micro on‐column cold trap/thermodesorption enrichment system for narrow bore columns is introduced and evaluated. The combination of considerable sample enrichment and preservation of the compatibility of the required input band width with column dimensions is critically examined. The process of thermodesorption (reinjection) which is the most critical step, is particularly emphasized.The system consists of a short aluminum coated fused silica or metal capillary with a low mass and a low cost electrical heating. Input band widths down to 1 ms are obtained without extreme demands on electrical power (300 watt). The potential of the system is illustrated with some extremely fast separations.
Analysis of volatile organic chemicals in aqueous samples by purge/GC with selective water removal
Authors: Cochran J. W. , Henson J. M. 
Published: May 2005

AbstractA gas chromatographic method for volatile organic chemicals in which an aqueous sample is purged directly to a cryogenically cooled, fused silica column uses a Nafion tube drier between the purge vessel and GC column. The Nafion strips water from the gas stream during the purge step while allowing volatile halocarbons and aromatics to continue to the GC column. Examples of this technique are presented on 0.53 mm and 0.25 mm fused silica columns coated with a variety of stationary phases.
Optimization of the cold split‐splitless injector in the solvent‐split mode
Authors: Termonia M. , Lacomblez B. , Munari F. 
Published: May 2005

AbstractIn this study, the cold split‐splitless injector recently introduced by Carlo Erba was optimized for the trace analysis of polycyclic aromatic hydrocarbons. Injections of hundreds of microliters of hexane solutions were performed in the solvent split mode using an autosampler programmed for large volume injection. Injection parameters such as type of insert, initial oven temperature, split time, and flow are shown to play important roles in defining the conditions for obtaining quantitative results. The loss of early eluting compounds can be minimized by achieving a solvent trapping effect, making use of n‐octane as co‐solvent in n‐hexane.
Cellulose acetate as stationary phase in microcolumn LC
Authors: Kiso Y. , Takayama K. , Jinno K. 
Published: May 2005

AbstractThe retention characteristics of alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) have been examined in liquid chromatography on a microcapillary column packed with cellulose acetate. Particulate and fibrous cellulose acetate were used as the stationary phase. Fibrous cellulose diacetate was found to be of use as an alternative stationary phase for liquid chromatography, although the separation efficiency was low. The retention characteristics for planar PAHs were linearly correlated with the size of the molecules, but the retention behavior for alkylbenzenes and nonplanar PAHs was affected by exclusion. The retention order was strongly influenced by the addition of dimethylformamide or water to methanol in the mobile phase. The results suggested that the retention behavior is influenced by a slight change in the polymer matrix of cellulose acetate.
Applications of coupled LC‐GC: A review
Authors: Davies I. L. , Markides K. E. , Lee M. L. , Raynor M. W. , Bartle K. D. 
Published: May 2005

AbstractAlthough coupled liquid chromatographygas chromatography (LC‐GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC‐GC applications have been published in the last two years (1987–88) alone. This review categorizes LC‐GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled‐column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on‐line trace enrichment‐GC) have also been included in this review.
Direct and automatic capillary GC analysis for molecular weight determination and distribution in crude oils and condensates up to C20
Authors: Durand J. P. , Fafet A. , Barreau A. 
Published: May 2005

AbstractA direct and automatic method has been developed for molecular weight (MW) determination and distribution in crude oils and condensates up to C20 (340°C) by gas chromatography. Chromatographic separation has been achieved with a 50 m OV‐1 fused silica capillary column, fitted with a pre‐column to eliminate the fraction boiling above 340°C. The internal standard is added for quantification. Approximately 550 peaks have been identified by the use of GC/MS on different paraffinic, naphthenic, and aromatic crude oils or condensate samples. From identification and by correlation with MS group‐type analysis, a carbon number and a hydrocarbon group are attributed to each peak or group of peaks. Further molecular weights have been calculated from these groups. A comparison between results from this GC method and cryometry of narrow and wide fractions shows good agreement, within the precision of cryometry. An automatic identification by computer using programmed temperature indices was used for the direct determination of molecular weight. The final report gives weight percentage, molar percentage, and molecular weight for every boiling range group and hydrocarbon group.
Evaluation of a PTV injector for quantitative analysis of volatile compounds at low concentrations
Authors: Herraiz M. , Reglero G. , Herraiz T. 
Published: May 2005

AbstractThe performance of a PTV injector operated in the solvent venting mode with Tenax in the glass insert was evaluated with synthetic mixtures containing 5 to 50 ng of n‐alkanes, ethyl esters, n‐alcohols, and carboxylic acids.The influence of the sampled amount, the injected volume, and the nature of the solvent on accuracy and precision were studied.Coefficients of variation of relative (normalized) peak areas and absolute peak area ratios of each compound to the standard are of the order of 5 %.
Enantioselective capillary gas chromatography on the basis of host‐guest interactions with modified cyclodextrins
Authors: König W. A. , Krebber R. , Wenz G. 
Published: May 2005

AbstractThe use of per‐O‐alkylated as well as partially alkylated/acylated derivatives of α‐, β‐, and γ‐cyclodextrins as chiral stationary phases has opened many new applications to enantioselective gas chromatography. Chiral recognition is now independent of hydrogen bonding interactions and enantiomer separations are achieved for a large variety of compounds which could not be separated before, including lactones, spiroacetals, alkyl halides, olefins, and even compounds with axial asymmetry.
Rapid and quantitative extraction and analysis of trace organics using directly coupled SFE‐GC
Authors: Hawthorne S. B. , Miller D. J. , Krieger M. S. 
Published: May 2005

AbstractSupercritical fluid extraction can be coupled with capillary gas chromatography (SFE‐GC) using commercially‐available on‐column or split/splitless injection ports. While liquid solvent extractions require several hours or even days to perform, SFC‐GC analyses can be completed in ≤ 1 hour including extraction, analyte concentration, and GC separation. SFE‐GC yields chromatographic peak shapes that compare favorably with those obtained using conventional liquid solvent injections. Quantitative extraction and recovery of analytes is usually achieved in 10 minutes, and maximum sensitivity is obtained since the extracted analytes can be quantitatively transferred into the GC column for cryogenic focusing prior to GC analysis. SFE‐GC analysis of a variety of organic pollutants from environmental solids and sorbent resins, and flavor and fragrance compounds from food products will be discussed.
How to avoid water contamination in the thermodesorption cryofocusing technique. Application to ethane analysis in human breath by means of an ion trap detector (ITD)
Authors: Ghoos Y. , Hiele M. , Rutgeerts P. , Vantrappen G. 
Published: May 2005

AbstractThe purpose of this study was to modify an automatic pre‐concentration system to avoid water contamination and to apply this technique to ethane analysis in breath. The ion trap detector was very useful in monitoring the whole analytical procedure.
Investigation of antioxidants and UV stabilizers from plastics. Part I: Comparison of HPLC and SFC; preliminary SFC/MS study
Authors: Arpino P. J. , Dilettato D. , Nguyen Khoa , Bruchet A. 
Published: May 2005

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 CO2 as 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.
Determination of free fatty acids in milk and cheese procedures for extraction, clean up, and capillary gas chromatographic analysis
Authors: De Jong Catrienus , Badings Herman T. 
Published: May 2005

AbstractA rapid, reliable and precise capillary gas chromatographic method for routine quantification of short‐ and long‐chain free fatty acids (FFA) in milk and cheese is described. Procedures of (1) lipid extraction, (2) isolation of the FFA from milk and cheese extracts, and (3) capillary gas chromatographic analysis were developed and optimized. FFA can be extracted from cheese for 95–100% with ether‐heptane after grinding with sodium sulfate and addition of 2.5 M sulfuric acid. From milk, 95–100 % of the FFA (≤ C8:0) are also extracted with ether‐heptane after addition of ethanol and 2.5 M sulfuric acid. Internal standards are used to compensate for the losses of lower FFA (C2:0–C8:0) in the aqueous phase. In view of the excellent recovery (98–100 %) and a considerable saving of time, the use of an aminopropyl column is preferred for the isolation of the FFA from lipid‐extracts. The underivatized FFA are separated directly by capillary gas chromatography making use of columns which enable accurate and rapid (≤ 40 min) determination of FFA C2:0–C20:0. With the method described, all major FFA (C2:0–C18:3) in milk and cheese can be quantified with good repeatability (rsd less then 2 %). The method is also applicable to the analysis of short‐chain fatty acids in other products.
Rapid determination of volatiles in alcoholic beverages by precolumn‐backflush gas chromatography
Authors: Hagman Gunnar , Roeraade Johan 
Published: May 2005

AbstractA method for quantitative determination of volatiles such as ethyl acetate, acetaldehyde, and methanol in alcoholic beverages is described. A short packed precolumn coupled to a capillary column via an effluent splitter is employed. The less volatile part of the sample is retained on the precolumn and back‐flushed using a 10‐port rotary valve, while the volatiles areseparated on the capillary column. The advantage of the system is that the analysis time per sample can be reduced to a few minutes. Moreover, the capillary column can be kept at low temperature, since it is not contaminated with material of low volatility.The water in the sample was found to have a significant influence on the retention of the compounds (as also observed earlier by Grob und Habich [1] ). This effect was exploited to increase the resolution between ethyl acetate and methanol, by injecting a portion of pure water prior to sample injection. Apart from the better separation, the water vapor also has a deactivating effect.The packed precolumn tolerates large amounts of non‐volatile material. Even after several hundred direct injections of wine and spirits, the chromatographic performance of the system was still satisfactory.
High‐performance liquid chromatography of proteins on short capillary columns
Authors: Mal'tsev V. G. , Nasledov D. G. , Trushin S. A. , Tennikova T. B. , Vinogradova L. V. , Volokitina I. N. , Zgonnik V. N. , Belenkii Boris G. 
Published: May 2005

AbstractA microchromatographic procedure for highly sensitive analysis of proteins has been developed by using short capillary columns with reverse‐phase, ion‐exchange, and hydrophobic interaction sorbents. The high analytical mass sensitivity on the level of several nanograms was attained by the miniaturization of the column and the optimization of gradient steepness.
Comparison of the SCD and FPD for HRGC determination of atmospheric sulfur gases
Authors: Gaines K. K. , Chatham W. H. , Farwell S. O. 
Published: May 2005

AbstractThe FPD and the new SCD have been examined for their respective performance characteristics as sulfur selective detectors for HRGC in the determination of atmospheric sulfur gases. Overall, the SCD was an extremely selective and sensitive sulfur gas detector with lower MDLs than the FPD and fewer problems with interferences and noise stability, thus allowing the SCD more flexibility in capillary column selection. Modification of the FPD, however, provided more symmetrical peaks and greater resolution than the Sievers Model 350 SCD.
HRGC of wine free amino acids as a tool for elementary wine characterization
Authors: Vasconcelos Ana M. P. , das Neves Higuinaldo J. Chaves 
Published: May 2005

AbstractIn this paper we show that wine free amino acids derivatized as isopropyl N‐heptafluorobutyryl esters can be used as a tool for wine characterization. Elementary wines of eight Vitis vinifera varieties were studied during a seven year period. The characteristic wine amino acids for each variety were assessed by means of pattern recognition techniques. A “star symbol plot” was used for graphic representation.
PTV vapor overflow — principles of a solvent evaporation technique for introducing large volumes in capillary GC
Authors: Grob Konrad 
Published: May 2005

AbstractThe concept of a GC solvent evaporation technique is outlined that involves a modified Programmed Temperature Vaporizing (PTV) injector. The vapor overflow technique is intended for introducing samples in large volumes of solvent by syringe injection of strongly diluted samples or by coupled LC‐GC. The liquid is introduced into a packed vaporizing chamber kept above the solvent boiling point at a pressure which is near or below ambient. The carrier gas is essentially switched off. Evaporation and discharge of the solvent vapors occurs by expansion of the vapors, driven by the solvent vapor pressure. For transferring the sapmple into the column, the carrier gas is switched on again and the vaporizing chamber heated.Compared to PTV solvent split injection, vapor overflow offers the following advantages: It automatically optimizes operational parameters, therefore facilitating its application. Losses of volatile materials are minimized by a minimal flow rate through the injector.Vapor overflow is a promising technique for transferring watercontaining eluents in coupled LC‐GC since no wettability is required and leaching of pre‐column surfaces is avoided.
Identification of active compounds in wheat straw extracts with allelopathic activity by HRGC‐MS and HRGC‐FTIR
Authors: das Neves Higuinaldo J. Chaves , Gaspar Elvira M. Monteiro 
Published: May 2005

AbstractThe allelopathic effects of decomposing wheat straw have been known for some time. In spite of the ecological and economical importance of the subject, only a limited number of compounds have been asociated with the allelopathic activity of wheat straw. In this study the high resolution, speed of analysis, and sensitivity of capillary gas chromatography coupled with mass spectromtry (HRGC‐MS) and Fourier transform infrared spectrometry (HRGC‐MS‐FTIR) have been used in a systematic study of the composition of biologically active wheat straw extracts. Droplet counter‐current chromatography (DCCC) was used for fractionation and isolation of components. The extract components were analyzed as methyl derivatives and free hydroxyl groups were located by means of ethylation with diazoethane. Twenty compounds were identified, most of them being phenolic acids. Naphthoic acid, azelaic acid and 1,2,3,5‐tetrabromobenzene were also identified.