bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular characterization of organically‐bound sulfur in crude oils. A feasibility study for the application of Raney Ni desulfurization as a new method to characterize crude oils
Authors: Damsté Jaap S. Sinninghe , Rijpstra W. Irene C. , de Leeuw Jan W. , Lijmbach Gerard W. M. 
Published: May 2005

AbstractFive crude oils with varying sulfur contents (0.1 – 4.7%) were characterized on a molecular level for organically‐bound sulfur. Aromatic fractions were analyzed by GC‐(MS) and asphaltene and polar fractions were analyzed by flash pyrolysis‐GC‐(MS). The polar fractions were also desulfurized with Raney Ni and the hydrocarbons formed were analyzed by GC‐MS. Major sulfur compounds in the aromatic fractions were identified as alkylbenzo‐ and alkyldiben‐zothiophenes. The flash pyrolyzates of the asphaltene contained alkylthiophenes and alkylbenzothiophenes as major compounds, depending on the thermal maturity of the oil. Generally, the sulfur‐rich crude oils contained relatively more sulfur compounds. The flash pyrolyzates of polar fractions contained a variety of sulfur compounds (alkylthiolanes, alkylthianes, terpenoid sulfides, alkylbenzothiophenes) with substantial differences between different crude oils. Raney Ni desulfurization of the polar fraction yielded hydrocarbons dominated by n‐alkanes, but isoprenoid alkanes, n‐alkylcyclohexanes, mid‐chain methylalkanes, tricyclic terpanes, hopanes and steranes were also present. These hydrocarbons show a potential to fingerprint crude oils since their distribution patterns are more characteristic than those of the hydrocarbons present in the saturated hydrocarbon fraction.
Coupled SFE/SFC/GC for the trace analysis of pesticide residues in fatty food samples
Authors: Nam Ki‐Souk , King Jerry W. 
Published: May 2005

AbstractAn on‐line SFE‐chromatographic system, where SFE has been coupled with SFC and GC, was developed and utilized for trace analyses of organochlorine and organophosphorus pesticide residues from gram‐sized complex sample matrices, such as chicken fat, ground beef, and lard. The SFE process and chromatographic techniques were instrumentally integrated for efficient and automated on‐line analysis, having minimal sample handling between the sample preparation and separation steps. A cleanup step, incorporating packed column SFC, allowed the fractionation of relatively small‐sized, non‐polar pesticides from the co‐extracted fatty materials. This permitted final high‐resolution separation of analytes on a capillary GC column. Detection of pesticides was accomplished using selective electron‐capture and nitrogen‐phosphorus detectors. Pesticide concentrations determined with the on‐line system were accurate and reproducible, for fatty samples containing both fortified and incurred pesticides. This method, utilizing supercritical carbon dioxide, was considerably faster and less laborious than the conventional analytical procedures based on liquid extraction.
Improving GC‐MS screening analysis by functional‐group‐related silica gel fractionation of industrial wastewater extracts
Authors: Reemtsma Thorsten , Jekel Martin 
Published: May 2005

AbstractThe separation of the components of complex industrial waste water extracts according to their functional groups has been accomplished by use of small silica gel columns eluted with a hexane – dichloromethane – methanol gradient. The six fractions obtained covered a polarity range from aliphatic fatty acids to (aromatic) polyhydroxy and polyether compounds. Recovery of model compounds was between 75 and 105%.Used prior to GC‐MS analysis this fractionation substantially enhances chromatographic resolution and facilitates peak identification. The procedure was exemplarily applied to an extract of anaerobically treated tannery waste water. Phenols, aromatic acids, and aromatic and aliphatic (poly)hydroxy acids, in the low ppm range, were determined as main constituents. Since fractionation extends the range of detection, trace substances such as chlorocresol, dichlorobenzoic acid, mercaptobenzothiazole, and mercaptoacetic acid were also detectable at the ppb level.
Capillary zone electrophoresis with indirect UV detection: Determination of sodium dodecyl sulfate in simulated stream water
Authors: Gibbons Jean M. , Hoke Steven H. 
Published: May 2005

AbstractSDS (sodium dodecyl sulfate) has been quantitatively determined by capillary zone electrophoresis using a fused silica capillary and a 5 mM dihydroxybenzoic acid / sodium hydroxide buffer in 5% methanol solution at a pH of 8.1. The ion was detected by indirect UV absorption at 250 nm. Detection range was from 0.8 to 50 mg SDS/L. This rapid method requiring only small sample volumes was developed in support of an aquatic toxicology study in a simulated stream water and is applicable to waters containing common inorganic ions.
Capillary zone electrophoresis of neutral organic molecules in organic – aqueous solution
Authors: Shi Youchun , Fritz James S. 
Published: May 2005

AbstractVery good separations of non‐ionic organic compounds have been achieved by capillary zone electrophoresis (CZE) using a tetrahep‐tylammonium salt as an additive in aqueous acetonitrile as solvent. A systematic study was undertaken to determine the effect of experimental parameters on electroosmotic mobility and electro‐phoretic mobility. It was found that pH, acetonitrile concentration, and the type and concentration of quaternary ammonium salt are important experimental variables. Under appropriate conditions, the separation window was enlarged and a broad range of electrically neutral organics, including very hydrophobic compounds (e. g. poly‐cyclic aromatic hydrocarbons) and fairly hydrophilic compounds were separated in a relatively short time. By adjusting the separation conditions, high resolution CZE of a specific group of neutral organic compounds could be achieved. A method for calculation of capacity factor was proposed and capacity factors for a variety of non‐lonic organic compounds were calculated.
Splitless injection of large volumes of aqueous samples: Further experience. Experiments on analyzing triazines by direct injection of drinking water
Authors: Grob Konrad , Fröhlich Dieter 
Published: May 2005

AbstractConditions were optimized for the introduction of large volumes of drinking water by splitless injection with vapor overflow, experimenting with the determination of triazines. No co‐solvent was added, and the maximum injection volume was 400 μl. A vapor outlet beyond a coated precolumn was used to discharge water vapors released belatedly from the packing. Using alkali flame ionization detection (AFID), detection limits were around 0.5 μg/l.
Detection of nitro musks in human fat by capillarv gas chromatography with atomic emission detection (AED) using programmed temperature vaporization (PTV)
Authors: Linkerhägner Manfred , Stan Hans‐Jürgen , Rimkus Gerhard 
Published: May 2005

AbstractAtomic emission detection (AED) has been successfully applied to the determination of nitro musks in the fat of human adipose tissue by gas chromatography at trace concentration levels. Element specific detection with the AED combined with a clean‐up procedure for nonpolar substances makes target screening analysis for lipophilic nitro aromatic compounds possible for the first time. The lack of sensitivity, especially in the AED nitrogen and oxygen trace, was compensated by higher concentration of the extracts and injection of larger sample volumes performed by cold programmed temperature vaporization (PTV) in the solvent split mode. The combination of the superior quantification properties of the atomic emission detector with large sample volume introduction makes the quantification of nitro musks down to the ppb level possible. All five nitro musks investigated exhibit linear dynamic ranges going down close to instrumental limits of detection. Moreover, organochlorine compounds could be sensitively detected in the same sample extract by the AED chlorine trace without any interferences from coeluting matrix compounds.
PCB separation by HRGC‐MS. Fourier analysis for characterizing Aroclor chromatograms
Authors: Pietrogrande Maria C. , Pasti Luisa , Dondi Francesco , Rodriguez Maria H. Bollain , Diaz Maria A. Carro 
Published: May 2005

AbstractAroclor and Aroclor mixture chromatograms obtained using temperature programmed high resolution capillary GC coupled with mass spectrometric selective detection have been investigated by Fourier analysis developed for the study of multicomponent chromatograms. The experimental autocorrelation function (EACF), i.e. peak shape and position correlation, showed a retention ‐ structure pattern which could be associated with both the type of Aroclor and the ion used for selective ion monitoring (m/z value). In particular, o‐m and m‐m isomerization effects were singled out by EACF analysis. By fitting EACF with previously developed theoretical models, it was possible to characterize a specific Aroclor in terms of the number of PCB congeners present in it. The results obtained agreed closely with the typical Aroclor content. For the Aroclor mixture, the distribution of inter‐distance between successive peaks was derived. The two first distribution moments obtained agreed with those derived from retention data reported in the literature. The consequences on the separation performance, i.e. the number of singlets, doublets, etc. in the chromatogram, are discussed.
Gas chromatographic separation of polychlorinated biphenyls on a new apolar capillary column
Authors: Vetter Walter , Luckas Bernd , Biermans Frans , Mohnke Manfred , Rotzsche Harald 
Published: May 2005

AbstractEighty one polychlorinated biphenyls (PCBs) and nineteen chlorinated pesticide standards have been analyzed on a newly developed apolar high resolution gas chromatography (HRGC) column. Emphasis was placed on the determination of PCB indicator congeners which are part of national regulations, and of toxic coplanar PCB congeners.The new column enables almost unambiguous quantification of the PCB indicator congeners (PCB 138 can be separated from both PCB 163 and PCB 164; PCB 28 and PCB 31 were also separated and no coelution was observed for PCB 52, PCB 118, and PCB 180). The new column furnished better results than CP‐Sil 8 for the analysis of PCB indicator congeners in a sample of seal blubber.
Volatile enrichment on automatic static headspace using a precolumn and stopping the carrier gas flow during injection
Authors: Barcarolo Robertino , Casson Pierino 
Published: May 2005

AbstractThe aim of this study was to develop a technique for performing automatic static headspace analysis of volatiles without a cryogenic device. Reconcentration of solutes was accomplished using a graphitized carbon coated precolumn between two splitting points and stopping carrier gas flow during injection. Chromatographic profiles of volatile compounds from ground coffee compared with split and splitless injections provide confirmation of the good sensitivity of the technique. The analysis of a standard mixture covering a wide range of volatility confirms that the described technique might be useful to achieve enrichement of low volatile headspace compounds, even if discrimination against the various components is present.
Artifact formation from the use of potassium‐iodide‐based ozone traps during atmospheric sampling of trace organic gases
Authors: Helmig Detlev , Greenberg Jim 
Published: May 2005

AbstractTrace atmospheric gases have been sampled using potassium‐iodide‐based reactant traps for ozone removal. GC‐MS analysis revealed the presence of organic iodine compounds which were present neither in the atmosphere nor as contaminants of the materials used, but more likely arose from reactions of organic gases or aerosols sampled with reactive iodine or hypoiodite released from reaction of ozone with potassium iodide in the traps. Losses of the individual organic trace gases measured were not, however, observed as a result of this mechanism. Several cautions in identifying unknown compounds from the atmosphere when using potassium iodide ozone traps are discussed.
Determination of organophosphorus pesticides in whole/chocolate/skim‐milk and infant formula using solid‐phase extraction with capillary gas chromatography/flame photometric detection
Authors: Ronald Erney D. 
Published: May 2005

AbstractTwenty nine organophosphorus pesticides (OPPs) are identified on a DB‐17 capillary column using gas chromatography‐flame photometric detection (GC‐FPD). An acetone‐acetonitrile mixture is used to initially extract OPPs from milk and infant formula samples, followed by partition of the analytes into dichloromethane (DCM). Dichloromethane is removed on a rotary evaporator and the residue taken up in acetonitrile (ACN) for cleanup on a C‐18 (octadecylsiloxane bonded silica) (SPE) cartridge. ACN eluate is evaporated under nitrogen and the residue taken up in acetone for GC‐FPD determination.Initial studies showed mean recoveries for 28 of 29 OPPs in whole milk fortified at 0.10 ppm ranged between 69 and 99% with a relative standard deviation (RSD) of 1.0–9.7%. Whole/chocolate/skim‐milk and four infant formula products fortified at 0.02 ppm gave mean recoveries of 64–103% with RSDs between 1.9 and 20.9% for 24 of 29 OPPs. Excluding skim milk, recoveries for Dichlorvos, Methamidophos, Mevinphos E, and Acephate ranged between 47 and 89%. Sample extracts were extremely clean and posed no difficulty to the GC system. The procedure is faster and less costly than Association of Official Analytical Chemists (AOAC) procedures and allows for determination of a broad spectrum of OPPs.
Capillary GC on 50 micrometer I.D. Columns coated with thick films. Theory and selected practical results
Authors: Steenackers Dirk , Sandra Pat 
Published: May 2005

AbstractThe chromatographic performance of 50 μm internal diameter (i.d.) fused silica columns coated with up to 2 μm films of immobilized SE‐54 (methyl phenyl (5%) silicone) is evaluated under gas chromatographic conditions. The influence of pressure drop on the plate height is discussed. In comparison to thick film 250–530 μm i.d. columns, much higher efficiencies and faster analyses are obtained. Practical examples, performed on a standard GC instrument, illustrate the features of thick film 50 μm i.d. columns.
Quantitative analysis of selected PCB congeners in marine matrix reference materials using a novel cyanobiphenyl stationary phase
Authors: Hillery Barbara R. , Girard James E. , Schantz Michele M. , Wise Stephen A. 
Published: May 2005

AbstractA novel p,p‐cyanobiphenyl stationary phase (p‐cyanobiphenyl, p‐allyloxy methylpolysiloxane) has been evaluated for the GC investigation of polychlorinated biphenyls (PCBs). Several PCB congeners which coelute on the phases typically used for PCB analysis (e.g. 5% phenyl methylpolysiloxane) are separated on the p,p‐cyanobiphenyl phase, including the hexachlorobiphenyl congeners PCB 163, PCB 164, and PCB 138. In this work, a p,p‐cyanobiphenyl stationary phase was used to measure selected PCB congeners in two Standard Reference Materials (SRMs) available from the National Institute of Standards and Technology (NIST), and two Certified Reference Materials (CRMs) available from the Community Bureau of Reference (BCR). The materials analyzed were SRM 1588, Organics in Cod Liver Oil; SRM 1945, Organics in Whale Blubber; CRM 349, Chlorobiphenyls in Cod Liver Oil; and CRM 350, Chlorobiphenyls in Mackerel Oil. Concentrations are reported for several PCB congeners which coelute on the 5% phenyl methylpolysiloxane, including PCB 163 and PCB 164.
Solid phase microextraction/isothermal GC for rapid analysis of complex organic samples
Authors: Górecki Tadeusz , Pawliszyn Janusz 
Published: May 2005

AbstractSolid phase microextraction (SPME) was used as the sample introduction technique for high‐speed isothermal GC. An injector dedicated for SPME fiber injection was designed and built. The injector was operated in two modes, continuously heated and flash heated. The latter mode proved to be better for high‐speed separations. The injector was then used for sample introduction in separation of BTEX. When sampling directly from water with a fiber having a 56 μm thick poly(dimethylsiloxane) coating, the BTEX components were separated under isothermal conditions in ca. 18 s. A fiber with a thinner coating (15 μm) enabled the separation to be completed in ca. 12 s when sampling from headspace. In both cases the results were highly reproducible, as measured by the estimated values of the relative standard deviation.
Micellar electrokinetic chromatography in coated capillaries: Determination of micelle–aqueous partition coefficients
Authors: Janini George M. , Muschik Gary M. , Issaq Haleem J. 
Published: May 2005

AbstractA micellar electrokinetic chromatography method is presented for the determination of the partition coefficient for the distribution of nonpolar and moderately polar solutes between the micelle and the aqueous phases in aqueous micellar solutions. In comparison with the literature the method is, theoretically and experimentally, the most straightforward for this application. An equation is derived for the determination of the partition coefficient in a coated fused silica capillary, with neglible electroosmotic flow, from simple measurements of the migration times of solutes and a marker for micelle migration. The advantages and limitations of this method are discussed. The method is tested by using sodium dodecylsulfate (SDS) surfactant and naphthalene, benzene, toluene, and phenol solutes. Micellar electrokinetic chromatography in coated columns isideally suited for the separation of hydrophobic solutes in aqueous samples.
Optimization of separations of alkyl‐substituted phenolate anions by capillary zone electrophoresis
Authors: Benz Nancy J. , Fritz James S. 
Published: May 2005

AbstractAnions of alkylphenols have very similar electrophoretic mobilities in CZE owing to their very small differences in size and the narrow range of their pKa values. By studying electrophoretic mobility as a function both of pH and of the amount of acetonitrile in the electrolyte solution, optimum separation conditions were determined. It was possible to separate a group of methyl‐substituted phenols, including several positional isomers. Mixtures containing n‐propyl and isopropyl phenols and 1°, 2°, and 3° butylphenols could be resolved.
HPLC separation of the enantiomers of racemic benzergoline derivatives on a chiral binaphthalene covalently bonded to silica gel
Authors: Küsters Ernst , Dosenbach Cornelia 
Published: May 2005

AbstractA novel chiral stationary phase (CSP) derived from the atropisomeric enantiomer S‐3,3′‐dicarboxy‐2,2′‐dihydroxy‐1,1′‐binaphthyl (S‐DDBN) has been synthesized and its use for the separation of enantiomers demonstrated. The chiral selector is covalently bonded to amino‐functionalized silica gel, thus enabling the use of alcohols as mobile phases. Good chiral discrimination was obtained for the pharmacologically interesting class of benzergoline derivatives which act as selective dopamine D1 receptor agonists. This paper reports the successful separtion of fifteen structurally related benzergoline racemates with separation factors up to 3.5. The influence of small differences in molecular structure on chiral discrimination was examined.
Gas chromatographic separation of the enantiomers of flumecinol and some related compounds
Authors: Reinhardt R. , Engewald W. , Görög S. 
Published: May 2005

AbstractFlumecinol and related compounds can, without derivatization, be separated into their enantiomers by gas chromatography on cyclodextrin phases; permethylated β‐cyclodextrin dissolved in OV‐1701 can be particularly recommended. Thermodynamic data describing the different intensities of interaction of the individual enantiomers with the stationary phases were determined. The values measured imply different separation mechanisms for the compounds investigated.
An automatic sampling device for capillary zone electrophoresis
Authors: Kaljurand M. , Ebber A. , Somer T. 
Published: May 2005

AbstractAn automatic sampling device has been developed for capillary zone electrophoresis. The sample is introduced to the column electrokinetically by rapidly exchanging buffer for sample in a narrow channel drilled in a plexiglass block. The autosampler is capable, under computer control, of performing multiple sample injections from a large volume sample source (such as a reaction vessel) as the sample concentration changes, and thus presents the possibility of analyzing time‐varying processes by CZE. Peak area reproducibility in electropherograms obtained after use of the sampler is less than 1% and efficiency is more than 2.2 × 105 theoretical plates.
Characterization of silicones by direct‐deposition GC/FT‐IR
Authors: Bonanno Anthony S. , Griffiths Peter R. 
Published: May 2005

AbstractMaterials used in the manufacture of silicone breast prostheses were analyzed by supercritical fluid chromatography (SFC) and high temperature gas chromatography (GC) coupled with direct deposition FT‐IR detection. The chromatographic resolution and deposition quality were found to be unsatisfactory for SFC/FT‐IR; however, high temperature GC/FT‐IR produced excellent results. The chromatograms and spectra obtained allowed for the identification of poly‐dimethyl silicones and mono‐, di‐, and tri‐diphenylsubstituted poly‐dimethyl silicones. An automated method of baseline correction was developed that allowed functional group chromatograms due to molecules containing Si‐phenyl bonds to be constructed without significant interference from Si‐methyl bonds despite the fact that the Si‐C stretching mode of Si‐phenyl bands overlapped significantly with the strong bands due to Si‐CH3 groups.
Use of capillary gas chromatography/sensory analysis as an additional tool for sampling technique comparison in peach aroma analysis
Authors: Rizzolo Anna , Lombardi Patrizia , Vanoli Maristella , Polesello Stefano 
Published: May 2005

AbstractCapillary GC/sensory analysis was used to judge if dynamic headspace on sliced pulp and on intact fruit, and solvent extraction could collect the “character impact” and the “contributory” aroma compounds in peaches. Capillary GC/sensory data showed that the headspace techniques selectively recovered the “contributory” volatile compounds, which are strictly related to the characteristic odor of the various peach cultivars, whereas solvent extraction better quantified the “character impact” compounds (lactones).
Chromatographic quantitation using fractions of the peak areas
Authors: Pires Valente Antonio L. , Augusto Fabio , da Rocha Eduardo Carasek 
Published: May 2005

AbstractQuantitative chromatographic analysis is liable to errors due to peak asymmetry because the uncertainty in the detected position of the end of the peak tail decreases the reliability of the computed peak area. This dependence may be a severe drawback whenever peaks of different areas must be compared, as in the case of calibration curves. A new approach to overcome the uncertainties of area calculation due to peak asymmetry is reported in this paper. The approach consists of calculating only the area included between the start and the maximum of the chromatographic peak. Simulated and experimental chromatographic data were used in this study. Both the peak start‐to‐peak maximum area (SMA) and the start‐to‐end or total area (TA) were calculated and the quantitative results were compared. Within the scope of this work it is concluded that the SMA yields calibration curves that are more linear and have intercepts closer to zero than the calibration curves obtained using the TA.