bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractCapillary 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

AbstractA 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

AbstractThe 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

Abstractn‐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

AbstractThe 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

AbstractA 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.
Detection of sugar addition to citrus juices by capillary GC
Authors: Cornil Vera , Ooghe Wilfried , Sandra Pat 
Published: May 2005

AbstractA 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

AbstractIn 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

AbstractThe 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

AbstractA 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

AbstractOpen 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

AbstractThis 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

AbstractThe 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

AbstractA 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

AbstractPerdeuterated 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractAn 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

AbstractTemperature 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

AbstractA 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

AbstractThe 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).