bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of congeners of polychlorinated biphenyls in reference materials
Authors: Anderson Jerry W. 
Published: May 2005

AbstractAroclor reference materials from the United States Environmental Protection Agency repository are proposed for use as secondary standards for the congener‐specific analysis of polychlorinated biphenyls in environmental samples. Representative samples of the materials have been analyzed using a gas chromatograph equipped with photo‐ionization and electron capture detectors. The elution pattern of the congeners was determined for a DB‐17 capillary column.
Coupled LC‐GC: The capacity of silica gel (HP)LC columns for retaining fat
Authors: Grob Konrad , Kaelin Iren , Artho Anna 
Published: May 2005

AbstractMany applications of coupled LC‐GC in food analysis require that LC separates large quantities of triglycerides from the components of interest. The capacities of silica gels to retain triglycerides have been determined for n‐hexane as mobile phase as well as some eluent mixtures. Conclusions are drawn for practical applications.
Molecular diffusivity of sample solutes in a number of eluents and the implications with regard to the design of capillary chromatographic systems
Authors: Korenaga Takashi , Izawa Miyoko , Fujiwara Takashi , Takahashi Teruo 
Published: May 2005

AbstractThe properties of sample solutes and eluents injected into capillary tubes were studied in order to develop improved chromatographic instrumentation technology. Use of a new apparatus to determine molecular diffusion coefficients (D) of solutes in both aqueous and organic eluents under laminar flow conditions provided results more rapidly than older methods. The experimental results obtained were in agreement with theoretical predictions and will be useful in the design of chromatographic systems.
Capillary columns in series for GC analysis of volatile organic pollutants in atmospheric and alveolar air
Authors: Clair Pascal , Tua Mireille , Simian Hervé 
Published: May 2005

AbstractAnalysis of volatile organic compounds in air samples requires high resolution capillary gas chromatography. When the sample contains both polar and non‐polar compounds, use of only one type of stationary phase can be unsuitable if it leads to the preferential separation of one kind of component having the same polarity at the expense of the separation of other classes of component.This paper describes the coupling of fused silica capillary columns of different polarity and length in order to achieve the separation of such complex mixtures. The combination is evaluated with a 42 component standard mixture and then applied to various atmospheric air samples and alveolar air of exposed subjects to demonstrate the capabilities of the complete sampling and separation technique.
Comparison by capillary SFC and SFC‐MS of soxhlet and supercritical fluid extraction of hamster feces
Authors: Pinkston J. David , Delaney Thomas E. , Bowling Donald J. , Chester Thomas L. 
Published: May 2005

AbstractComponents of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds.SFC with flame ionization detection was used to compare Soxhlet extraction, off‐line supercritical fluid extraction (SFE), and on‐line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent.
The effects of the column pressure drop on retention and efficiency in packed and open tubular supercritical fluid chromatography
Authors: Janssen Hans‐Gerd , Snijders Henri M. J. , Rijks Jacques A. , Crarners Carel A. , Schoenmakers Peter J. 
Published: May 2005

AbstractThe effects of the pressure drop across the column on retention and efficiency in SFC have been studied. Numerical methods are described which enable the prediction of hold‐up time and pressure drop in both packed and open tubular columns. Predictions of both hold‐up time and pressure drop are in good agreement with experimental data.The density gradient along the column can be calculated using the numerical methods and a procedure is described which enables the calculation of the overall capacity factors of the solutes from the density profile in the column. Significant variations of the capacity factor are observed along the column.The effect of the density gradient along the column on local diffusivity and dispersion is studied. The column efficiency in systems with significant pressure drops is affected by changes in: the linear velocity of the mobile phase; the diffusion coefficients; and the capacity factors of the solutes along the column. The overall efficiency of the chromatographic system can be calculated if, as is the case for open tubular columns, adequate plate height equations are available.
A different operational mode for addressing the general elution problem in rapid analysis gas chromatography
Authors: Rubey Wayne A. 
Published: May 2005

AbstractThe task of chromatographically separating a complex mixture containing constituents with a wide range of molecular weight has been referred to in the past as the “general elution problem”. A different operational mode for conducting gas chromatography, thermal gradient programmed gas chromatography, presently in the developmental stage, has been investigated and is proposed as a means whereby such separations might be accomplished rapidly. The inherent versatility of the technique for conducting rapid analyses (50 to 300 s duration) of complicated samples containing constituents with a wide range of volatility is considered in terms of the possibility of achieving the maximum amount of analytical information per unit time.
On the complementary nature of CGC‐MS, CGC‐FTIR, and CGC‐AED for water pollution control
Authors: David Frank , Sandra Pat 
Published: May 2005

AbstractUnequivocal identification of unknown pollutants is very difficult if only one dimension of information is used. Combining different hyphenated techniques can, on the other hand, lead to more reliable identification. Combination of the data provided by the different techniques is more important than on‐line combination of the techniques themselves.
Estimation of the size of liposomes by modified HDC
Authors: Molina F. J. , Vila A. O. , Llácer C. , Martos M. J. , Figueruelo J. E. 
Published: May 2005

AbstractInternal calibration in modified hydrodynamic chromatography has been realized by the approach of Prieve and Hoysan, i.e. the use of polystyrene monodisperse latexes to evaluate the equivalent capillary radius, R. The value obtained has been used to estimate the average sizes of a variety of liposome samples from egg yolk lecithin.
Capillary gas chromatography of tert‐butyldimethlysilylamino acids with PTV injection
Authors: das Neves H. J. Chaves , Vasconcelos A. M. P. 
Published: May 2005

AbstractThe programmable temperature vaporizing injector (PTV) has been used to study the effects of injection temperature and initial heating period on the FID response factors of TBDMS derivatives of 17 protein amino acids. The relative response factors were calculated for injection temperatures of 50°C, 90°C, 160°C, 220°C, and 260°C with different initial heating periods (1 s, 5 s, and 10 s) and the results compared with the values obtained for the calculated response factors obtained under classical split injection conditions (300°C, continuous). Except for expected peak broadening effects, the initial heating period does not seem to have significative effects on relative peak areas. The response to the derivatives of alanine, glycine, α‐aminobutyric acid, valine, proline, methionine, cysteine, phenylalanine, asparagine, and arginine was only slightly affected by increasing the injection temperature whereas the response factors for the derivatives of serine, threonine, glutamic acid, lysine, histidine, tyrosine, and tryptophan were strongly dependent upon initial injection temperatures, decreasing rapidly at temperatures above 160°C. The cold split‐splitless injection is clearly advantageous over the classical hot injection techniques for the analysis of this type of aminoacid derivative.
Multiple headspace extraction‐capillary gas chromatography (MHE‐CGC) for the quantitative determination of volatiles in contaminated soils
Authors: Maggio A. , Milana M. R. , Denaro M. , Feliciani R. , Gramiccioni L. 
Published: May 2005

AbstractA multiple headspace extraction‐capillary gas chromatographic method for the quantitative, accurate, and rapid determination of volatiles in multicontaminated soil samples has been developed. A thick film fused silica column has been used and a nine‐step multiple headspace extraction (MHE) determination performed. Calibration was achieved by introducing 1 μl of a standard solution of mixed volatiles into empty headspace vials, the presence of the matrix being unnecessary in multiple headspace extraction. Accuracy of determination by MHE‐CGC and a simple method employing standard additions have been compared.
The use of alternative fluids in on‐line supercritical fluid extraction – capillary gas chromatography
Authors: Levy Joseph M. , Storozynsky Eugene , Ravey Robert M. 
Published: May 2005

AbstractA key feature differentiating analytical supercritical fluid extraction (SFE) from conventional liquid extraction is the possibility of varying the solvent strength of a supercritical fluid to achieve selective extractions of specific target compounds, or functional classes of compound, from complex matrices. This can be accomplished by using supercritical fluids other than carbon dioxide, for example, sulfur hexafluoride, nitrous oxide, or sulfur hexafluoride‐modified carbon dioxide. The use of these fluids will be demonstrated by the characterization of complex environmental and petroleum matrices by directly coupled SFE – capillary GC. On‐line SFE‐GC involves the decompression of pressurized extraction fluid directly into the heated, unmodified capillary split injection port of the chromatograph. This paper will also show how, by adjustment of the extraction temperature and pressure, SFE selectivity may be further enhanced.
Analysis of nucleic acid derivatives by micellar electrokinetic capillary chromatography
Authors: Lecoq Anna‐Francesca , Leuratti Chiara , Marafante Erminio , Di Biase Sebastiano 
Published: May 2005

AbstractThe use of micellar electrokinetic capillary chromatography (MECC) for the analysis of the major nucleobases, nucleosides, and nucleotides, and their chemically modified derivatives, has been developed and refined. The dimensions of the separating capillaries, the composition of the buffering systems, and the conditions used for electrophoresis were investigated in order to obtain the best performance.Particular emphasis was placed on the identification of the physiological constituents of nucleic acids and their chemically modified analogs: in vitro studies on calf thymus DNA exposed to genotoxic agents have demonstrated that adducted bases and nucleolides can be identified by MECC.
Determination of lidocaine in human serum by capillary gas chromatography with surface ionization detection
Authors: Arimoto Hiromi , Shiomi Koichi , Fujii Toshihiro 
Published: May 2005

AbstractA novel analytical method has been developed for the determination of lidocaine (2‐(diethylamino)‐N‐(2,6‐dimethyl)phenylacetamide) in human serum. After solvent extraction from serum the extract was analyzed by gas chromatography employing a van den Berg type solventless injector, a new sensitive and selective detector, the surface ionization detector, and a bonded phase flexible fused silica capillary column. The detection limit was ca. 30–50 ng/ml.
High resolution capillary gas chromatographic hydrocarbon‐type analysis of naphtha and gasoline
Authors: Shiomi Koichi , Shimono Masao , Arimoto Hiromi , Takahashi Seiji 
Published: May 2005

AbstractA slightly modified, commercially available high resolution capillary gas chromatograph and a PC‐based data processing system running proprietary software (“PONA”) have been employed in the development of a system for petroleum type analysis which would be equivalent or superior to the FIA (fluorescent indicator adsorption) method in terms of ease of use and the speed, variety, and accuracy of the analytical data produced.The system is capable of performing identification and quantitation of most of the individual components in a complex gasoline sample consisting of more than 230 components and can report weight percentage and/or volume percentage for each component as well as types by carbon number (e.g., isoparaffins, normal paraffins, olefins, naphthenes, aromatic compounds) within a ca. 70 minute analysis cycle.Precolumn sulfonation to trap olefins and aromatic compounds has been used as an complementary technique to the basic mass spectrometric identification of components of interest. The estimation of correction factors for weight percentage (or volume percentage) calculation are also discussed. Comparisons are made between this system and others, and the results indicate that the proposed method supersedes the conventional method employing FIA.
Influence of intramolecular interaction on the enthalpy and entropy of methylene unit sorption for the homologous series of carbonyl‐containing compounds analyzed by capillary GC
Authors: Golovnya Rimma V. , Grigoryeva Diana N. , Vasilyev Alexei V. 
Published: May 2005

AbstractThe enthalpy and entropy of sorption of methylene units in the homologous series of n‐alkyl acetates; methyl, n‐butyl, and phenyl n‐alkyl ketones; and the methyl esters and chloroanhydrides of n‐aliphatic carboxylic acids have been determined on an SE‐54 capillary column. The enthalpy of sorption of the first methylene unit is anomalously high when the growing n‐alkyl chain is connected directly to a carbonyl group. This effect is a result of intramolecular interaction between neighboring methyl and carbonyl groups. It has been shown by measurement of the enthalpy and entropy of sorption of the difluoromethylene unit in the series of n‐hexyl esters of perfluorinated carboxylic acids that for these compounds the effect is absent.The intramolecular interaction was found to increase in the order methyl butyl ketone < methyl phenyl ketone < methyl acetate < acetyl chloride < acetone.
Elution order in gas chromatography
Authors: Mehran Mehrzad , Cooper William J. , Golkar Nahid , Nickelsen Michael G. , Mittlefehldt Eric R. , Guthrie Edward , Jennings Walter 
Published: May 2005

AbstractThe retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature‐programmed conditions. Both ΔHv (enthalpy of solute vaporization from the stationary phase) and ΔSv (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value.
Ozone‐based sulfur chemiluminescence detection: Its applicability to gas, supercritical fluid, and high performance liquid chromatography
Authors: Howard Angela L. , Taylor Larry T. 
Published: May 2005

AbstractThe sensitive detection of sulfur‐containing analytes is of interest in many industrial applications; selective detection is also desirable since these compounds are usually present at trace levels in difficult matrixes. The purpose of this article is to review the use of the Sievers® ozone‐based sulfur chemiluminescence detector, and its coupling with gas chromatography, supercritical fluid chromatography, and high performance liquid chromatography. Detection limits, linearity, response factors, and selectivity are discussed for each of these techniques. Critical operational parameters for the SCD are also described. The use of other sulfur selective detectors for SFC and HPLC is also briefly summarized.
Determination of streptomycin in pharmaceutical preparations by gas chromatography
Authors: Arrowood Susan , Hoyt Arthur M. , Woods Mark W. 
Published: May 2005

AbstractThe antibiotic streptomycin can be reliably quantitated in injectable pharmaceuticals by GC. The manipulations are not difficult, and total analysis time for duplicate samples is less than twenty minutes.Reaction of the drug with aqueous sodium hydroxide solution generates maltol, which is extracted into chloroform prior to silylation. The silyl ether of maltol is then assayed, using naphthalene as internal standard. Duplicate analyses of twenty pharmaceutical samples showed a relative standard deviation of ±1.3%.
Enantiomeric resolution of underivatized small peptides by HPLC with a chiral crown ether stationary phase
Authors: Esquivel Benjamin , Nicholson Lawrence , Peerey Linda , Fazio Michael 
Published: May 2005

AbstractFactors influencing the stereoisomeric resolution of underivatized dipeptides and a representative tripeptide on Crownpak (CR) columns have been investigated. The elution order and relative retention suggest that a combination of chiral, steric, and hydrophobic interactions effects the extent of chiral recognition and the retention achieved during separations. Some dipeptides whose amine terminus is located three atoms from the asymmetric center (such as dipeptides of D,L‐glycine) were resolved, but the elution order was the opposite of that expected for the type of Crownpak column used (CR(+)). Peptides containing hydrophobic substituents were strongly retained, but their retention times could be significantly reduced, and detectability improved, by use of gradient elution. Analysis of a commercial sample of D,L‐leucine‐D,L‐alanine revealed the stereoisomers to be present in an unexpected quantitative ratio and demonstrated the utility of these separations for quality assurance and quantitative analyses.
Comments concerning the HPLC separation of acrolein from other C3 carbonyl compounds as 2,4‐dinitrophenylhydrazones: A proposal for improvement
Authors: Dye Christian , Oehme Michael 
Published: May 2005

AbstractThe separation of the toxicologically important aldehyde acrolein from other carbonyl compounds by high performance liquid chromatography after derivatization to 2,4‐dinitrophenylhydrazones is critically discussed on the basis of a selection of published methods. A method is proposed whereby the compounds acrolein, acetone, and propanal may be reproducibly separated to baseline by a reversed phase HPLC procedure employing a ternary mixture of methanol, water, and acetonitrile as mobile phase.
Prediction, optimization of separation, and identification of unknown compounds in capillary gas chromatography
Authors: Guan Yafeng , Zheng Peng , Zhou Liangmo 
Published: May 2005

AbstractA procedure for the identification and separation of unknown compounds by capillary gas chromatography is described. The procedure involves a live retention time database and optimization of the separation. After initial chromatography of the sample, a rough search lists all the possible compounds it might contain and the analyst then uses his experience to discard those compounds in the list which are unlikely to be present. The multi‐component separation is then optimized over the whole range of defined starting temperatures and programming rates, in order to produce the best possible separation of the sample components, and the chromatography repeated using the results obtained from the optimization procedure. Further search operations within a given search window will then report the compound names, and related information, for each peak.Since the identification operation is performed at least twice during the procedure, and the optimization of the separation assists the identification by separating possibly overlapped peaks, the confidence of the qualitative analysis is higher than may be obtained using standards alone. If the reproducibility of isothermal indices measured on columns could be guaranteed, this procedure could be used instead of performing chromatography on standards of the compounds contained in the database, regardless of changes in column dimensions, phase ratio, and operating conditions in temperature programmed analysis.
Investigation of the detection limit for the determination, by pyrolysis‐capillary GC, of the thickness of ultra thin PMMA layers coated on to PET film
Authors: Jin Xigao , Oguri Naoki , Onishi Akira , Uchino Sigeki 
Published: May 2005

AbstractThe determination of nanometer thick layers of poly(methyl methacrylate) coated on to the surface of poly(ethylene terephthalate) film has been investigated by high resolution pyrolysis gas chromatography without sample pretreatment or modification of the instrumentation used. A good linear relationship was observed between the quantity of the characteristic pyrolysate and the thickness of the poly(methyl methacrylate) layer; the detection limit was sufficient to enable the quantitation of poly(methyl methacrylate)‐to‐poly(ethylene terephthalate) film thickness ratios of 1:20000 in composite materials.
Improving detection limits in chromatography by signal averaging
Authors: Ghaoui Labib , Rothman L. David 
Published: May 2005

AbstractEnsemble or signal averaging has been used to increase detection limits in gas chromatography. The sample is injected several times into a gas chromatograph and the chromatograms generated are summed. The resulting chromatogram is treated as a separate chromatogram with the benefit of an improved signal‐to‐noise ratio. Use of the technique enables reliable quantitation, the time invested being used to convert an unacceptable signal‐to‐noise ratio into useful data. A discussion and some applications of the technique are described.
Use of carbon adsorption traps combined with high resolution gas chromatography – mass spectrometry for the analysis of polar and non‐polar C4‐C14 hydrocarbons involved in photochemical smog formation
Authors: Ciccioli Paolo , Cecinato Angelo , Brancaleoni Enzo , Frattoni Massimiliano , Liberti Arnaldo 
Published: May 2005

AbstractA method has been developed for the collection and analysis of polar and non‐polar C4‐C14 hydrocarbons involved in the formation of photochemical smog. Enrichment of hydrocarbons from both polluted and unpolluted areas has been achieved with three‐stage traps packed with carbon adsorbents of different surface area; the use of a home‐made desorption unit employing cryofocusing then enables the determination of the compounds by HRGC‐FID. Two‐stage traps filled with graphitic carbon have been used prior to GC‐MS identification and quantitation of compounds producing overlapping peaks.The methodology has been tested in the urban area of Rome and in a pine forest, and more than 140 different compounds identified and quantitated. Many of the constituents were found to be oxygenated, either formed by photochemical reactions or of anthropogenic origin.