bluuebunny/crossref_metadata_2025 huggingface dataset:
MDGC–MS: A powerful tool for enantioselective flavor analysis
Authors: Full Gerhard , Winterhalter Peter , Schmidt Gertraut , Herion Peter , Schreier Peter
Published: May 2005

This 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

The 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

Deactivation 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

Xenon 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

Capillary 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

A 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

An 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

Peak 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

The 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

HTHRGC 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

The 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.
The use of combined LC‐GC for the analysis of fuel products: A review
Authors: Kelly Grant W. , Bartle Keith D.
Published: May 2005

A review of the analysis of petroleum fuels, oils, tars and engine exhaust particulate extracts by on‐line coupled LC‐GC is presented.
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

This 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

The 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

Series 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

A 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.
Use of a long‐spacer‐side‐chain liquid crystalline polysiloxane containing a crown ether as a stationary phase for capillary gas chromatography
Authors: Zhou Wei , Fu Ruonong , Dai Rongji , Huang Zaifu , Chen Yanfei
Published: May 2005

A new kind of side chain liquid crystalline polysiloxane containing a crown ether with a longer spacer (PSC‐11) has been prepared and coated on a fused silica capillary column. The main chroma‐tographic characteristics including efficiency, polarity, and selectivity have been examined. The phase exhibits the retention properties of both liquid crystal and crown ether stationary phases and possesses higher efficiency and better selectivity than PSC‐3, which has a shorter spacer between the main polysiloxane chain and liquid crystalline side chain.
Gas chromatographic enantiomer separation of agrochemicals and polychlorinated biphenyls (PCBs) using modified cyclodextrins
Authors: Hardt Ingo H. , Wolf Christian , Gehrcke Bärbel , Hochmuth Detlev H. , Pfaffenberger Bernd , Hühnerfuss Heinrich , König Wilfried A.
Published: May 2005

The enantiomers of the polychlorinated polycyclic xenobiotics heptachlor, cis‐ and trans‐chlordane, cis‐ and trans‐heptachlorepoxide, oxychlordane, and bromocyclen have been resolved by gas chromatography with selectively substituted cyclodextrins. The order of elution of these compounds and of α‐hexachlorocyclohexane (α‐HCH) was determined by comparison with enantiomerically enriched reference compounds obtained by preparative enantioselective gas chromatography.

A separation of the eight stereoisomers of the pyrethroid insecticide allethrin into seven peaks was achieved. Both trans‐diastereomers were separated into their enantiomers and the order of elution could be determined by comparison with commercially available (S)‐bioallethrin and trans‐bioallethrin. Also one cis‐diastereomer was separated, wheras the other cis‐isomer could not be resolved. In addition 15 out of 19 stable atropisomeric polychlorinated biphenyls with 5, 6 and 7 chlorine substituents, some chiral organophosphorus pesticides, including acephate and malaoxon and the herbicide bromoacil were separated.
Continuous liquid‐liquid extraction combined on‐line with capillary gas chromatography‐atomic emission detection for environmental analysis
Authors: Goosens Elise C. , Jong Dirk De , de Jong Gerhardus J. , Rinkema Feddy D. , Brinkman Udo A. Th.
Published: May 2005

The on‐line coupling of a liquid‐liquid extraction system with capillary gas chromatography using atomic emission detection (GC‐AED) has been studied. The required large volumes of about 100 μl of an iso‐octane solution can be introduced into the GC‐AED system by using the AED solvent vent and a solvent vapor exit in front of the capillary analytical column. Test solutions containing several pesticides were detected using the carbon, chlorine, nitrogen and sulfur channels. Analyte detectability (in concentration units) was improved significantly and low concentractions of the test compounds could be determined (1–5 ng/ml). Aqueous samples were on‐line extracted and analyzed. The precision of the large‐volume injection itself as well as the total extraction‐GC‐AED system was satisfactory (RSD of ca. 2 and 4%, respectively). As a real‐life application, several ground water samples were screened.
Capillary zone electrophoresis for polymide composition analysis
Authors: McNair Harold M. , Sun Xiaowei
Published: May 2005

Capillary zone electrophoresis (CZE) was employed in polyimide composition analysis. Polymide was decomposed to its corresponding aromatic diamine and aromatic acid monomers by an alkali fusion reaction. Sample treatment is much simpler than published methods, and electropherograms show a good separation of decomposed products under the proper conditions.
Increased on‐column injection temperature for gas chromatography
Authors: Janák Karel , Colmsjö Anders , Östman Conny
Published: May 2005

A way of controlling the maximum allowable oven temperature during on‐column injection by the column pressure drop is suggested. An arrangement using a restriction at the column outlet for adjustment of the column inlet pressure while maintaining the same column flow has been studied. Compared to non‐restricted flow, substantially increased maximum oven temperatures were obtained during on‐column injection. Injections at elevated temperatures resulted in an increased speed of analysis and decreased solute adsorption on the surface of the contaminated retention gap. The method is generally applicable to analysis of high boiling mixtures. In particular, with GC‐AED, such an arrangement yields a higher sensitivity due to an increased solute interaction with the excitation plasma.
Diluted modified cyclodextrins as chiral stationary phases – influence of the polysiloxane solvent: Heptakis(2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin
Authors: Dietrich Armin , Maas Birgit , Mosandl Armin
Published: May 2005

The influence of different polysiloxane solvents on the efficiency and stereoselectivity of columns coated with mixtures of heptakis (2,3‐di‐O‐acetyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin and the polysiloxanes was investigated. Generally, the enantioselectivity increased with decreasing polarity of the silicone solvent and/or increasing cyclodextrin concentration, with some exceptions. Thermodynamic investigations showed that a change of the diluting phase or the cyclodextrin concentration affects entropy as well as enthalpy differences between the diastereomeric cyclodextrin/solute complexes. As a consequence, a certain cyclodextrin/polysiloxane combination is superior to another only at a particular temperature.
Identification of FAMEs using ECL values and a three‐dimensional Kováts retention index system
Authors: Antoniosi Filho Nelson R. , Lanças Fernando M.
Published: May 2005

n‐Alkanes and fatty acid methyl esters have been chromatographed on four capillary columns of different polarity (LM‐1 (100% polydimethylsiloxane), CB‐225 (25% cyanopropyl, 25% phenyl polysiloxane), LM‐100 (immobilized polyethylene glycol), and BPX‐70 (70% cyanopropyl polysiloxane)) with the goal of identifying the major fatty acid methyl esters obtained by derivatization of vegetable oils. Chromatographic retention data were employed for the construction of a three‐dimensional Kováts retention index system and for the elaboration of a table of equivalent chain length values.
The effect of capillary column diameter on the performance of thermal conductivity detectors
Authors: Blumberg Leonid M. , Dandeneau Raymond D.
Published: May 2005

The concentration sensitivity of a thermal conductivity detector (TCD) depends, among other factors, on the amount of sample mixture in the detector's sensing cell. Since the cell volume has to be appropriately matched with column diameter, it makes the concentration sensitivity of a TCD dependent on column diameter and, therefore, on the speed of gas chromatography. Through reduction of column diameter, higher speed tends to lead to a reduction in the concentration sensitivity of the cell. The factor which the most directly affects the concentration sensitivity of a TCD cell is the heat power conducted through the cell. The higher the power, the greater the sensitivity. The limit of detection of a TCD depends on the concentration‐sensitivity of its cell and on the level of statistical errors in the measurement. The errors increase with increasing analysis speed. As the column diameter is reduced, the errors cause additional worsening (on top of the decrease in concentration sensitivity) of the detection limit, dynamic range, and other performance characteristics of the TCD.
Analysis of airborne substances by means of microwave thermal desorption
Authors: Scharf Juliane , Sarafin Rolf
Published: May 2005

A method has been developed to enable thermal desorption of airborne substances from solid adsorbents based on active charcoal by means of microwave energy, followed by on‐line GC‐FID analysis. Ceramic traps were filled with 50 mg of commercially available graphitized carbon black. Adsorption efficiency and desorption conditions for three substances covering a broad range of vapor pressure were investigated. The recovery rate, breakthrough, and linearity of the system were determined by direct fortification with standard solutions, followed by microwave thermal desorption and gas chromatographic separation. The recovery efficiencies were 80–84 %, with a standard deviation of 3–6 %. The correlation coefficient of the linear range between 1 (10 for one of the compounds) and 1000 ng was > 0.999. Initial experiments were performed to investigate the enrichment of the standards from the gaseous state. The recovery rates of the most volatile compound was increased by optimizing the density of the packing.
Chromatography in the ancient world?
Authors: Ettre Leslie S.
Published: May 2005

Indications that already in the Ancient World, methods based on chromatographic principles were utilized, are discussed. As pointed out, they had little to do with chromatography.
Detection of sugar addition to citrus juices by capillary GC
Authors: Cornil Vera , Ooghe Wilfried , Sandra Pat
Published: May 2005

A method is described for the detection of citrus juices adulterated by addition of industrial sugar products. The oligosaccharides maltotriose (DP3) and maltotetraose (DP4), both of which are absent from the natural sugar profile of citrus fruits, serve as markers. The sample preparation method includes clean‐up on a solid phase ODS cartridge, fractionation of DP3 and DP4 carbohydrates by LC on aminopropyl silica gel, and derivatization of the collected sugars to form the oxime‐trimethylsilyl derivatives. Capillary GC analysis is performed on a 30 m × 0.32 mm i.d. polydimethylsiloxane fused silica column applying cool on‐column injection and FID detection. The detection limit for maltotriose and maltotetraose is about 1 mg l−1. Several orange and grapefruit juices were evaluated on their authenticity. Adulteration with crystalline sugar products cannot be detected with the described procedure.
Cyclodextrin derivatives for GC separation of racemic mixtures of volatile compounds. Part VIII: 2,6‐di‐O‐methyl‐3‐O‐pentyl‐γ‐cyclodextrin and 2,6‐di‐O‐methyl‐3‐O‐(4‐oxo‐pentyl)‐ and 2,6‐di‐O‐pentyl‐3‐O‐(4‐oxo‐pentyl)‐β‐and ‐γ‐cyclodextrins
Authors: Bicchi Carlo , D'amato Angela , Manzin Valeria , Galli Anna , Galli Mario
Published: May 2005

In pre vious papers, 2,6‐di‐O‐methyl‐3‐O‐pentyl‐β‐cyclodextrin (CD) was demonstrated to be successful in separating volatile compounds, while avoiding the drawbacks of 2,3,6‐tri‐O‐methyl‐O‐methyl‐β‐CD in terms of column stability and operating temperature.

Since a CD chiral selector of universal use has not yet been found, and at least two (or more) columns coated with different CD derivatives are therefore necessary for routine work, the performance of 2,6‐di‐O‐methyl‐3‐O‐pentyl‐γ‐CD, 2,6‐di‐O‐methyl‐3‐O‐(4‐oxopentyl)‐γ‐CD, 2,6‐di‐O‐pentyl‐3‐O‐(4‐oxo‐pentyl)‐β‐CD, and 2,6‐di‐O‐pentyl‐3‐O‐(‐4‐oxo‐pentyl)‐γ‐CD diluted in polysiloxanes for the separation of volatile compounds in aromas and essential oils will be illustrated; each column coated with each of the newly synthesized CD derivatives was evaluated by analyzing more than 150 different recemates with different structures.
Gas chromatographic study of the thermal and analytical properties of a nematic luquid crystal and its cupric complex
Authors: Berdagué P. , Perez F. , Courtieu J. , Bayle J. P. , Abdelhadi O. , Guermouche S. , Guermouche M. H.
Published: May 2005

The nematic compound N‐4‐(2′‐(4″‐dodecyloxybenzoyloxy)‐4′‐do‐decyloxy)azobenzenyl‐4‐dodecyloxysalicylideneimine, known as LH, and its cupric complex, bis[N‐4‐(2′‐(4″‐dodecyloxybenzoyloxy)‐4′‐dodecyloxy)azobenzenyl‐4‐dodecyloxysalicylidene]iminato of copper (II), known as CuL2 have been used as stationary phases for gas chromatography. The thermal properties of LH and CuL2 have been determined with conventional metal columns, using n‐alkanes as solute probes. Plots of In V0g against 1/T clearly show the temperature transitions of LH and CuL2. The analytical capabilities of the two stationary phases were established by use of 25 m glass capillary columns. Satisfactory separations were obtained for positional hydrocarbon and halocarbon isomers, aromatic and polyaromatic compounds, and volatile essential oil constitutents.
An improved version of an old fluorocarbinol chiral stationary phase
Authors: Pirkle William H. , Selim Adel I.
Published: May 2005

A chiral stationary phase (CSP) derived from anthrone is quite effective for the chromatographic resolution of the enantiomers of a wide variety of compounds. Denoted CSP 4, the phase is a chiral 2,2,2‐trifluoro‐1‐(9‐anthryl)ethanol tethered to silica by an elevencarbon‐atom chain at the 10‐position of the anthryl ring. CSP 4 typically provides greater enantioselectivity than its fluoroalcohol predecessor and is synthetically much more accessible.
Open tubular supercritical fluid chromatography of triterpene acids from Dysoxylum pettigrewianum (Meliaceae)
Authors: Sewram Vikash , Nair Jerald J. , Mulholland Dulcie A. , Raynor Mark W.
Published: May 2005

Open tubular supercritical fluid chromatography (SFC) with carben dioxide as the mobile phase has been investigated for the separation of four triterpene acids, two of which were structural isomers. These compounds, isolated from Dysoxylum pettigrewianum (Meliaceae), were chromatographed on three stationary phases with different selectivities. 30%‐biphenylmethylpolysiloxane and polyethylene glycol (Carbowax 20M) phases exhibited poor chromatographic selectivity for the compounds. The separation was improved by employing the shape selectivity of a liquid crystalline biphenylcarboxylate ester polysiloxane and utilizing simultaneous temperature and pressure programming. The elution order was explained on the basis of the molecular structures of the triterpene acids, and their interaction with the liquid crystal phase.
The analysis of C4–C11 hydrocarbons in naphtha and reformate with a new apolar fused silica column
Authors: Estel Dietrich , Mohnke Manfred , Biermans Frans , Rotzsche Harald
Published: May 2005

This paper deals with the separation of alkanes, naphthenes, and aromatic compounds in naphtha and reformate, on a newly developed apolar high resolution GC column. The selectivity of this apolar phase has been compared with those of squalane, DB‐1, and SE‐30. A total of 95 hydrocarbons were reliably identified, mostly by GC‐MS. Repeated measurements of Kováts retention indices are presented as evidence for the reproducible manufacture of fused silica columns coated with this phase.
Selectivity trends in packed column supercritical fluid chromatography with C18 stationary phases
Authors: Williams Karen L. , Sander Lane C. , Page Steven H. , Wise Stephen A.
Published: May 2005

The retention behavior of polycyclic aromatic hydrocarbons (PAHs) in packed‐column supercritical fluid chromatography (SFC) is studied for monomeric and polymeric C18 columns. 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 SFC.
Study on the thermal stability of a chiral stationary phase coated on capillaries for GC
Authors: Takeichi Tsutomu , Yada Hiroshi , Takayama Yuzi , Morikawa Masami
Published: May 2005

A chiral stationary phase prepared by bonding L‐valine‐t‐butylamide to XE‐60 has been coated on glass and metal capillaries. The performances of the chiral glass and metal columns were equivalent to those of commercial fused silica capillary columns. The thermal stability of the glass column was examined up to 280°C. It was found that no appreciable change in separation factor (α value) was observed up to 230°C. The α values gradually decreased between 240 and 260°C, and enantiomer separation was no longer achieved at 280°C. It was concluded that the allowable upper limit temperature of the chiral stationary phase is between 230 and 240°C in the isothermal mode, and ca 260°C in temperature‐programmed mode.
Synthesis, isolation, and chromatography of perdeuterated α‐1,2,3,4,5,6‐hexachlorocyclohexane
Authors: Vetter Walter , Luckas Bernd
Published: May 2005

Perdeuterated α‐1,2,3,4,5,6‐hexachlorocyclohexane (α‐PDHCH) was synthesized and isolated in pure form. α‐PDHCH was baseline separated from unlabeled α‐HCH by high resolution gas chromatography on different stationary phases. α‐PDHCH was also resolved into its enantiomeric forms by application of a chiral GC phase. Furthermore, chiral chromatography of a mixture of labeled α‐PDHDH and unlabeled α‐HCH resulted in four peaks. Standard solutions of α‐PDHCH are recommended both as recovery standard for sample clean‐up and as internal standard for the quantitation of chlorinated hydrocarbons with GC/MS or GC/ECD in environmental samples.
Analysis of fragrances in cosmetics by gas chromatography–mass spectrometry
Authors: Rastogi Suresh Chandra
Published: May 2005

A gas chromatographic (GC)‐mass spectrometric (GC‐MS) method has been developed for the routine analysis of 11 fragrance substances in cosmetics: cinnamic alcohol, cinnamic aldehyde, eugenol, hydroxy citronellal, α‐amyl cinnamic aldehyde, geraniol, isoeugenol, coumarin, dihydrocoumarin, citronellal and citral. Methods for sample preparation of various types of cosmetic products, prior to GC analysis, have also been developed and proved to be rugged. Detection limits of all of target fragrance substances were approximately 1 ppm. Calibration curves of the target fragrance substances analyzed by GC were found to be linear in the investigated concentration range, 0.005% – 0.50%. The recoveries of the target fragrances from various types of cosmetic products were 80% – 116% and the relative standard deviations of the quantitative analysis of the target fragrance substances were within 5%.
Separation of binaphthyl enantiomers by capillary zone electrophoresis and electrokinetic chromatography
Authors: Nishi Hiroyuki
Published: May 2005

The capillary electrophoretic (CE) separation of the enantiomers of three binaphthyl compounds is investigated. Several CE modes such as cyclodextrin (CD) modified capillary zone electrophoresis (CZE) (CD‐CZE), micellar electrokinetic chromatography (MEKC), cyclodextrin electrokinetic chromatography (CD‐EKC), etc. are employed for the simultaneous enantiomer separation of the three solutes. The successful separation was achieved by combining two modes, in other words by using more than two chiral selectors. A development of the CE enantiomer separation is demonstrated for the binaphthyl compounds. The enantioselectivity of binaphthyl compounds is alo briefly discussed.
Determination of polychlorinated biphenyls in human blood plasma by on‐line and off‐line liquid chromatography–gas chromatography
Authors: Grimvall Eva , Östman Conny , Nilsson Ulrika
Published: May 2005

A method for the determination of non‐, mono‐ and di‐ortho substituted polychlorinated biphenyls in human blood plasma is presented. The non‐ortho CBs are isolated from the bulk of PCBs by HPLC on a dinitroanilino‐propyl silica column and collected as a heart‐cut fraction that is transferred on‐line to GC‐MS utilizing concurrent solvent evaporation technique. The on‐line coupling serves to lower the limit of determination and to partly automate the sample clean‐up. The di‐ and mono‐ortho CBs are analyzed by off‐line GC‐ECD using two different columns. Sample pre‐treatment is performed by extraction with organic solvents and fractionation on silica gel. A high reproducibility and an absolute over‐all recovery of approximately 70 % is demonstrated. The method is applied to samples of blood from 5 individuals. All the samples demonstrated a similar relative concentration profile. It was also shown that three CB congeners (CB 126, CB 156 and CB 170) contributed to the major part of the toxic equivalent quantity of the PCB content in the blood.
Effect of moisture on supercritical fluid extraction of polynuclear aromatic hydrocarbons and phenols from soil using an automated extractor
Authors: Ashraf‐Khorassani Mehdi , Combs Michael T. , Taylor Larry T.
Published: May 2005

An automated supercritical fluid extraction system was evaluated with polynuclear aromatic hydrocarbons and phenols to demonstrate extraction efficiency, collection efficiency, and sample cross contamination. Results showed that 75/25 glass beads/octadecyl silica provided the highest collection efficiency for these classes of compounds. Also, the automated SFE system was used to study the effect of different percentages of water (w/w) in soil on extraction efficiency of fortified PAH and phenols at different temperatures and pressures. Results showed that the presence of (available) water in soil (>10%) does, increase extraction efficiency of higher molecular weight PAH at higher temperature. Also it was demonstrated that temperature rather than pressure had a marked effect on extraction efficiency. The extraction efficiency of phenols from soil which contained 5% of water, using pure supercritical CO2, was higher than those obtained from dry soil or soil containing 1 % water. Extraction of phenols from soil did not show a dependence on pressure or temperature.
Environmental applications of large volume injection in capillary GC using PTV injectors
Authors: Mol Hans G. J. , Althuizen Mariken , Janssen Hans‐Gerd , Cramers Carel A. , Brinkman Udo A. Th.
Published: May 2005

Temperature programmable (PTV) injectors with packed widebore (ca. 3.5 mm i.d.) liners are used for large volume injection in capillary gas chromatography with the aim to simplify and/or improve off‐line sample pretreatment proecdures. A simple procedure for optimization of large volume PTV injection is described. The system performance, i.e. linearity and repeatability, is evaluated for polar nitrogen/phosphorus containing pesticides (PTV‐GC‐NPD) and organochlorine pesticides (PTV‐GC‐ECD) in river water extracts as well as for polycyclic aromatic hydrocarbons (PAHs) in river sediment (PTV‐GC‐MS).
Capillary zone electrophoretic separation of isomeric benzoic acids using cyclodextrin
Authors: Khaled Maha Y. , McNair Harold M.
Published: May 2005

A method using capillary zone electrophoresis has been developed for separation of a series of isomeric benzene polycarboxylic acids. The separation was found to depend largely on the geometry of the acids and their degree of ionization as well as on the buffer pH and composition. The presence of additives to the buffer such as cyclodextrin and cationic surfactants was found necessary for complete resolution of all the isomers.
Micellar and microemulsion electrokinetic chromatography of hop bitter acids
Authors: Szücs Roman , Hove Erik Van , Sandra Pat
Published: May 2005

The elution order of the hop α‐ and β‐acids has been studied under different modes of electrokinetic separation. A model is advanced to explain the shorter migration times of the more hydrophobic β‐acids compared to the α‐acids in micellar electrokinetic chromatography (MEKC). For quality control of the bitter principles in hops, the ruggedness of electrokinetic separation could be improved by replacing MEKC by microemulsion electrokinetic chromatography (MEEKC).
Evaluation of gas chromatography coupled with ion mobility spectrometry for monitoring vinyl chloride and other chlorinated and aromatic compounds in air samples
Authors: Simpson Greg , Klasmeier Maren , Hill Herbert , Atkinson David , Radolovich G. , Lopez‐Avila Viorica , Jones T. L.
Published: May 2005

The objective of this research was to evaluate, in the laboratory, the potential of gas chromatography/ion mobility spectrometry (GC/IMS) for monitoring vinyl chloride and other organic compounds in air samples in the field. It was determined that GC/IMS has the potential to directly detect vinyl chloride in air at the 2 ppbv level, and when concentrated on an adsorbent trap from a 1 L sample of air, detection could be lowered to the 0.02 ppbv level. From a comparative investigation of 18 EPA priority pollutants and 34 common vapor‐phase organic compounds, many compounds were found to provide a more sensitive response in IMS than vinyl chloride, indicating that GC/IMS would be broadly applicable to the direct detection of vapor‐phase organics in air.

Operating parameters including drift gas, spectrometer temperature, and sample‐inlet position were evaluated and discussed with respect to sensitivity and resolution. High temperature dramatically increased sensitivity to vinyl chloride. Vinyl chloride was shown to produce both negative and positive ion mobility spectra, with the negative‐mode spectra resulting from electron‐capture dissociation of the vinyl chloride. The limit of detection for vinyl chloride was found to be 7 pg/s. Limits of detection for 18 EPA priority pollutants were determined and compared to vinyl chloride. The responses of 34 other vapor‐phase organic compounds were also compared to that of vinyl chloride. Non‐selective, positive‐ion detection of 30 of the 34 compounds was demonstrated along with selective, electron‐capture‐type detection of 29 of them. Chloride‐specific and bromide‐specific detection illustrated the advantages of selected‐ion monitoring in IMS.
A modified inlet system for high speed gas chromatography using inert metal tubing with a carbon dioxide cooled cryotrap
Authors: Li Wenhai C. , Andrews Anthony R. J.
Published: May 2005

Ten different metal tubings were investigated for thermal decomposition of analytes when used as the trap tube in a cryotrap/thermodesorption inlet system. No noticeable sample decomposition of hydrocarbons, chlorinated hydrocarbons and a brominated hydrocarbon was observed for six of the tubings with hydrogen as the carrier gas. This observation may be partly attributed to the developed deactivation techniques that produce inert metal tubings that are being widely adopted by many column manufacturers, the different trap materials used in comparison to previous studies and the decreased sample residence time in the hot trap tube. A cryotrap using carbon dioxide was constructed and tested as a alternative to the previously used liquid nitrogen based systems. This cryotrap was able to trap compounds with a boiling point of 80°C.
Analysis of naturally occurring α‐acetotriacylglycerides by gas chromatography — chemical ionization mass spectrometry
Authors: Spitzer Volker , Aichholz Reiner
Published: May 2005

The seed oils of three Maytenus species have been examined by high temperature GLC using SOP‐50 (methoxy‐terminated) and OV‐225‐OH (OH‐terminated) glasscapillary columns. The main compounds (71–76%) could be identified as α‐mono‐acetotriacylglycerols by a combination of high temperature GLC‐MS in negative chemical ionization mode with a CH4/N2O mixture as reactant gas and other spectroscopical methods (infrared, 1H‐ and 13C‐nuclear magnetic resonance spectroscopy). The OV‐225‐OH phase demonstrated better separation properties that the SOP‐50 phase for this substance class and up to eight species of α‐monoacetotriacylglycerols could be separated. The content of usual triacyclglycerols was below 1%. The results of the analysis of the individual fatty acids as their methyl esters by GC and GC‐MS are also presented.
Alcohol modifiers in MEKC with SDS as surfactant. Study on the influence of the alcohol chain length (C1C12)
Authors: Van Hove Erik , Szücs Roman , Sandra Pat
Published: May 2005

The influence of alcohol modifiers with different chain length on the migration time window in micellar electrokinetic chromatography (MEKC) has been studied. Highly polar alcohols like methanol and 1‐propanol are typical aqueous phase modifiers. Higher alcohols like 1‐butanol, 1‐pentanol and 1‐hexanol influence the micellar structure and are considered as micellar phase modifiers. The effect of long chain alcohols is small because of their low applicable concentrations.
Deactivation of silica surfaces with a silanol‐terminated polysiloxane; structural sharacterization by inverse gas chromatography and solid‐state NMR
Authors: Scholten Alex B. , de Haan Jan W. , Janssen Hans‐Gerd , van de Ven Leo J. M. , Cramers Carel A.
Published: May 2005

Retention gape deactivated with Silicone OV‐1701‐OH show good chromatographic performance and remarkable stability against water induced stationary phase degradrdation. In an attempt to better understand the findamentals off the deactivation process using silanol terminated polysiloxanes, a fumed silica was deactivated with Silicon OV‐1701‐OH. In contrast to fused silic capillaries, fumed silica (Aerosil A‐200) can be studied by 29Si cross‐polarization magic‐angle‐spinning (CPMAS) NMR, thus serving as a model substrate for fused silica. Retention data from inverse gas chromatography at infinite dilurion and 29Si CP MAS NMR data of five Aerosil phases, differing in residual silanol surface concentration, are correlated with the aim of validating this approach for stationary phase characterization. A comparatively detailed model of the deactivating polymer layer that explains the observed absorption activities is deduced.

Surface silanols are shown to play a key role in the polymer layer, the structure of which is of primary importance for the absorption behavior after deactivation. Contrary to common belief, the absolute silanol surface concentration after deativation is only of secondary importance for the overall absorption activity. High silanol surface concentrations enhance degradation of the polysiloxane chains into small cyclic fragments as well as subsequent absorption and immobolization to the silica substrate surface. The mobility of linear polysiloxane chains in the kHz regime (as determined bby NMR cross‐polarization dynamics) appears to determine the extent which the residual silanols are accessible for analytes. It is therefore anticipated that there is an optimum silanol surface concentration of fused silica surfaces to be deactivated with silanol terminated polysiloxanes; it should be lazrge enough to adsord polymer fragments, but not large to avoid excessive residual silanol activity.
Modified capillary GC/MS system enabling dynamic headspace sampling with on‐line cryofocusing and cold on‐column injection of liquid samples
Authors: Barcatolo Robertiono , Casson Pierino
Published: May 2005

The paper describes a capillary GC/MS hardware arrangement allowong either:

on‐line injection of sample of gases and vapors coming from dynamic headspace or purg & trap samplers and their subsequent cryofocusing/thermal desorption prior to the analytical capillary column (first column):

direct injection of liquid samples through a cold on‐column injector into a second analytical column (counted in series with the first).

Chromatographic profiles of acacia honey aromas provide condirmation of the suitability of this system.
Investigation of fulvic acids from peat using capillary electrophoresis (CE)
Authors: Ciavatta Claudio , Govi Marco , Gessa Carlo
Published: May 2005

The aim of this work was to characterize the fulvic acids (FA) extracted from peat by use of capillary electrophoresis (CE). Two FA extracts have been obtained using two different extractants (0.1 M NaOH and 0.1 M NaOH plus 0.1 M Na4P2O7, Na+PP). The CE runs wre performed using a coated silica capillary, and several buffer solutions at different PH values. The results obtained show that the Fa extracts may be well characterized by CE even if the isolelectric point of the fulvic compounds is very low. The best fractionation has been obtained using a buffer borate at PH 8.9 as funning buffer. The charcterization of the two extracts also showed some important differences between the NaOH extract and the Na+PP extract.
Gas chromatographic separation of chiral organochlorines on modified cyclodextrin phases and results of marine biota samples
Authors: Vetter Walter , Klobes Ulkrike , Hummert Kerstin , Luckas Bernd
Published: May 2005

Four chiral stationary phases containing modified cyclodextrines diluted in or chemically bonded to a non‐chiral phase were used to resolve chiral organochlorine compounds such as α‐hexachlorocyclohexane (α‐HCH), perdeuterated α‐HCH (α‐PDHCH), β‐and γ‐pentachlorocyclohexene (PCCH), oxychlordane, cis‐and trans‐chlor‐ dane, cis‐ and trans‐heptachlorepoxide, PCB 95, PCB 132, PCB 149, and Chiral tozaphenes.

The elution order was determined by analyzing standards with known enantiomeric excesses.

Furthermore, an internal standard was used to even out slight variations in the ratio of peak hights of enantiomers which were determined from injection to injection.

None of the chiral stationary phases resolved all chiral organochlorine compounds. However, the β‐TBDM(35% heptakis (6‐O‐t‐butyldimethylsilyl‐2,3‐di‐O‐methyl)‐β‐cyclodextrin in OV 1701) column allowed the separation of all compounds under investigation except for PCB 95 and chiral toxaphenes.

Emphasis was placed on the separation of as many as possible enantiomers on a chiral phase by application of one temperature program and with respect to unambiguous quantitation of biological samples such as bludder and liver of marine and terrestrial mammals.