bluuebunny/crossref_metadata_2025_split huggingface dataset:
The advantages of evaporative light scattering detection in pharmaceutical analysis by high performance liquid chromatography and supercritical fluid chromatography
Authors: Lafosse Michel , Elfakir Claire , Morin‐Allory Luc , Dreux Michel 
Published: May 2005

AbstractThe evaporative light scattering detector (ELSD) has been used in pharmaceutical analysis by liquid and supercritical fluid chromatography. An ELSD equipped with interchangeable interfaces enables the use of various eluents (UV‐ or non‐UV‐absorbing) in isocratic or gradient mode. Analyses were performed on several non‐UV‐absorbing excipients and active substances. The narrow spread of the response factors of the various compounds investigated has indicated that the detector is suitable for direct raw quantitation of unknown samples in stability studies.
Determination of residual solvent in pharmaceutical preparations by static headspace GC
Authors: Penton Zelda 
Published: May 2005

AbstractStatic headspace GC, a simple, clean technique which is easily automated, appears to be a good approach to the determination of solvent residues in pharmaceutical preparations. The feasibility of this approach has been studied with an automated system.Data is presented for the solvents designated as impurities in pharmaceutical preparations by the United States Pharmacopeia. It was found that the static headspace technique meets the United States Pharmacopeia criteria for sensitivity. The absolute area count precision was <5% relative standard deviation and correlation coefficients to a linear response were >0.999. It was concluded that the technique is viable for this application.
Electrospray micro liquid chromatography – Fourier transform infrared micro spectrometry
Authors: Raynor Mark W. , Bartle Keith D. , Cook Bernard W. 
Published: May 2005

AbstractMicrocolumn liquid chromatography has been interfaced with infrared microspectrometry by means of a novel technique involving electrospray nebulization. The eluent from the LC column is subjected to a high positive potential relative to the surroundings and the electric field generated charges the surface of the emerging liquid causing it to disintegrate into charged droplets which are attracted to an earthed, infrared‐transparent, zinc selenide deposition plate. Nitrogen sheath gas is used to evaporate the solvent in the droplets, and the separated components are deposited on the zinc selenide plate for subsequent analysis by means of a Fourier transform infrared microscope and spectrometer. Provided low flow rates (∼4 μl/min) are used, total elimination of the solvent is achieved and easily identifiable infrared spectra can be measured from less than 500 pg of sample (caffeine).
New, selectively substituted cyclodextrins as stationary phases for the analysis of chiral constituents of essential oils
Authors: König Wilfried A. , Gehrcke Bärbel , Icheln Detlef , Evers Petra , Dönnecke Jürgen , Wang Weichao 
Published: May 2005

AbstractNew β‐ and γ‐cyclodextrin derivatives, selectively substituted with n‐pentyl and methyl groups, e.g. heptakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐β‐cyclodextrin, octakis(2‐O‐methyl‐3,6‐di‐O‐pentyl)‐γ‐cyclodextrin, and octakis(2,6‐di‐O‐methyl‐3‐O‐pentyl)‐γ‐cyclodextrin, have been prepared from specifically protected intermediates. The new cyclodextrin derivatives exhibit unique enantioselectivity towards important chiral constituents of essential oils. The enantiomers of lavandulol, α‐bisabolol, nerolidol, and other terpenoid alcohols could be resolved and their presence in different essential oils could be proved. Methyl jasmonate and epi‐methyl jasmonate could, in addition, be detected in jasmine concrete by two‐dimensional gas chromatography. The enantiomers of the macrocyclic ketone muscone have been separated for the first time.
Improved congener‐specific GC analysis of chlorobiphenyls on coupled CPSil‐8 and HT‐5 columns
Authors: Bøwadt Søren , Larsen Bo 
Published: May 2005

AbstractThe congener‐specific analysis of polychlorinated biphenyls (PCB) by high resolution gas chromatography on a 50 m × 0.25 mm fused silica column coated with a 0.26 μm film of 5% diphenyl polydimethylsiloxane (CPSil‐8) has been significantly improved by series coupling with a 25 m × 0.22 mm column coated with a 0.10 μm film of 1,2‐dicarba‐closo‐dodecarborane polydimethylsiloxane (HT‐5). Using helium as carrier gas, a total of 64 congeners in technical PCB mixtures could be analyzed as resolved peaks by ECD (86 by MS) with the CPSil‐8 column, and 84 by ECD (108 by MS) with the combination. The high upper temperature limit for these stationary phases (>300°C) enabled fast temperature programming and rapid analysis (60 min).
The analysis of lubricating oil additives by supercritical fluid chromatography with packed and open tubular capillary columns
Authors: Ashraf Sameena , Bartle Keith D. , Clifford Anthony A. , Moulder Robert 
Published: May 2005

AbstractLubricating oil additives have been analyzed by supercritical fluid chromatography on open tubular and packed capillary columns. Carbon dioxide and modified carbon dioxide were used as mobile phases and detection was accomplished by flame ionization and micro UV. Rapid and efficient analysis of the lubricating oil additives was demonstrated.
Identification and quantification of anticarcinogens in garlic extract and licorice root extract powder
Authors: Weinberg David S. , Manier M. Lisa , Richardson Mark D. , Haibach Frederick G. , Rogers Tina S. 
Published: May 2005

AbstractNine organosulfur compounds present in an aged garlic extract and two isoflavonoids and one triterpenoid present in a licorice root extract powder have been identified and quantified. Quantification involved solvent extraction and gas chromatographic – mass spectrometric analysis (garlic extract) or hydrolysis, solvent extraction, and liquid chromatographic analysis (licorice root extract powder).Although the garlic extract proved to be unstable and the concentration of the organosulfur compounds varied with time, one analysis of the extract gave the following results: methyl disulfide (0.607 μg/g), methyl trisulfide (0.181 μg/g), allyl sulfide (2.02 μg/g), allyl disulfide (0.784 μg/g), allyl trisulfide (0.795 μg/g), allyl methyl sulfide (1.64 μg/g), allyl methyl disulfide (0.411 μg/g), allyl methyl trisulfide (0.695 μg/g), and ethyl 2‐propenesulfinate (11.4 μg/g). The analysis of the licorice root extract powder gave the following results: formononetin (1.92 mg/g), isoliquiritigenin (9.61 mg/g), and 18β‐glycyrrhetinic acid (43.9 mg/g).Methods were successfully developed to quantify the same compounds in the serum of test animals which had consumed feed spiked with garlic extract or licorice root extract powder. Only the 18β‐glycyrrhetinic acid could be detected in the sera of such animals, however. An effort was also made to determine serum levels of prostaglandin E2 to correlate its inhibition with levels of the dietary components, but the prostaglandin E2 levels were too low to measure.
Cyclodextrin derivatives in the GC separation of racemic mixtures of volatile compounds: Part IV
Authors: Bicchi Carlo , Artuffo Giuseppe , D'Amato Angela , Galli Anna , Galli Mario 
Published: May 2005

AbstractThis paper reports the chromatographic performance of columns coated with 2,3,6‐trimethyl‐α‐, β‐, and γ‐cyclodextrins (2,3,6‐TriMe‐α,‐ β‐, and γ‐CD) and their derivatives 2,6‐dimethyl‐3‐trifluoroacetyl‐α‐, β‐, and γ‐cyclodextrins (2,6‐DiMe‐3‐TFA‐α‐, β‐, and γ‐CD), all six diluted in polysiloxane, for the separation of the enantiomers of volatile compounds.The influence of column length and film thickness on separation is reported. Phenomena related to reproducibility and consistency, over a period of time, of columns prepared with these CD derivatives are also discussed, and a possible solution to some drawbacks reported here is proposed.
Element‐selective atomic emission detection for capillary GC of metal‐containing compounds
Authors: Zeng Yadi , Seeley Jeffrey A. , Dowling Thomas M. , Uden Peter C. , Khuhawar Muhammed Y. 
Published: May 2005

AbstractElement‐selective GC detection by microwave‐induced plasma atomic emission spectroscopy has been used to examine a wide variety of compounds containing metals, non‐metals, and metalloids. “Recipes”, or new selective detection schemes for use with the software of the computer‐controlled system, have been developed for the selective detection of boron, aluminum, gallium, titanium, vanadium, chromium, manganese, rhenium, palladium, and platinum. Figures of merit including limits of detection, linear dynamic range, and spectral selectivity over carbon have been established for most of these elements. Gas chromatography – atomic emission detection (GC‐AED) has been applied to the selective detection of vanadium, nickel, and iron in metalloporphyrins present in crude oil, manganese‐selective detection of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline, and titanium‐selective detection of reaction mixtures containing titanium catalysts or titanium boride molecular precursors.
Modification of silica surfaces for CZE by adsorption of non‐ionic hydrophilic polymers or use of radial electric fields
Authors: Belder Detlev , Schomburg Gerhard 
Published: May 2005

AbstractPolyvinylalcohols (PVA) and hydroxyethylcelluloses (HEC) have been used as additives in cyclodextrin‐modified capillary zone electrophoretic chiral separations of aromatic amines such as tocainide and its analogs in unpretreated 50 μm i.d. fused silica capillaries. The additives were used at low concentrations (<0.05%) in common buffers, together with the γ‐cyclodextrin as chiral selector. They reduce the electroosmotic flow, i.e. increase the migration times of the analytes in these chiral separations, and, moreover, considerably improve both peak symmetry and the widths of the peaks relative to migration time. In terms of the chromatographic theory of efficiency, more than 200000 theoretical plates can be achieved with unpretreated fused silica capillaries. This enhancement of efficiency arises because adsorptive “dynamic” coating with the hydroxylic modifier molecules suppresses adsorption of the analyte molecules by the capillary walls.The influence of field strength and buffer composition on the separation efficiency attainable with and without modifier in the buffers has also been investigated. Alternative experiments on the influence of analyte adsorption on efficiency have been performed by superimposing radial electric fields on the capillary to modify the ζ potentials. Although the EOF could be freely adjusted, it was not possible to obtain an improvement in efficiency comparable with that furnished by coating the adsorptive surface with PVA or HEC.
Splitless injection of up to hundreds of microliters of liquid samples in capillary GC: Part II, experimental results
Authors: Grob Konrad , Brem Sandra 
Published: May 2005

AbstractSample evaporation in splitless injection of large volumes is rapid: depending on the experiment, results indicate that 200 μl of hexane, for instance, evaporates in 2–10 s, producing vapor at a rate of many hundreds of milliliters per minute. A 60 × 4 mm packed bed of 20–35 mesh Tenax TA enabled injection of 200 μl volumes of all solvents tested, and even 1 ml injections were possible provided they were performed over a period of 30 s. Retention of volatile sample components depends on the sample solvent, the injection volume, and the injection speed, but only little on the injector temperature. Losses of n‐tridecane varied from hardly 15 % (when dissolved in pentane) to ca 60 % (ethyl acetate); losses of n‐heptadecane were usually below 20 %. The column temperature during injection should be at least ca 20–30°C above the standard solvent boiling point.
An improved method of characterizing fatty acids by equivalent chain length values
Authors: Stránský Karel , Jursík Tomáš , Vítek Antonín , Skořepa Jiří 
Published: May 2005

AbstractA method has been developed for calculating more accurate and reproducible equivalent chain length (ECL) values of 33 straight‐chain fatty acids (FA), with various positions and numbers of cis double bonds, chromatographed on DB‐Wax and DB‐1 columns. The dependence of ECL values on the position and the number of double bonds is described, as is a method of utilizing these relationships for the characterization of FA by gas chromatography.
Environmental analysis of organic compounds in water using solid phase micro extraction
Authors: Arthur Catherine L. , Pratt Katherine , Motlagh Safa , Pawliszyn Janusz , Belardi Robert P. 
Published: May 2005

AbstractSolid Phase Micro Extraction (SPME) involves exposing a fused silica fiber coated with stationary phase to a contaminated water sample. The organic analytes become partitioned between the stationary phase and the water and when equilibrium is reached the fiber is removed from the solution and the analytes are thermally desorbed in the injector of a gas chromatograph. The fiber is contained in a syringe to facilitate handling.Factors which affect linear range, limit of detection, and total analysis time are discussed with regard to the development of a method for analysis of volatile compounds in environmental water samples. The sensitivity of the method was determined by the thickness of the film of stationary phase; the equilibration time, however, increased with the film thickness, although it can be minimized by use of a cross‐shaped stirrer bar.Increasing the thickness of stationary phase in the analytical column enables the cryofocusing temperature to be increased from −40 to −15°C. With an ion trap mass spectrometer, detection limits required by the US Environmental Protection Agency are met for all compounds except chloromethane and chloroethane. The method has been applied to environmental water samples.
Using electronic pressure programming to reduce the decomposition of labile compounds during splitless injection
Authors: Wylie Philip L. , Klein Kenneth J. , Thompson Michael Q. , Hermann Bruce W 
Published: May 2005

AbstractA split/splitless capillary injection port has been developed for electronic pressure programming (EPP) in gas chromatography. The inlet may be operated in several modes: constant pressure, constant flow, vacuum compensation (for gas chromatography–mass spectrometry (GC‐MS)), pressure‐programmed, or a combination mode enabling a pressure program to be followed by constant flow. A pressure‐programming technique has been tried which uses high pressure (high column flow rate) at the time of injection followed by reduction in inlet pressure to a value required for normal chromatography. Sample is swept rapidly from the inlet and into the column, reducing contact with the hot, active inlet surfaces which cause sample decomposition. The decomposition of endrin and 4,4′‐DDT, two labile pesticides, can be substantially reduced using this technique and modest improvements were also observed with the carbamate pesticide carbaryl.
The derivatization of fatty acids by (chloro)alkyl chloroformates in non‐aqueous and aqueous media for GC analysis
Authors: Vreeken Rob J. , Jager Maria E. , Ghijsen Rudy T. , Brinkman Udo A. Th. 
Published: May 2005

AbstractFatty acids can be conveniently derivatized in less than one minute with (chloro)alkyl chloroformates such as methyl chloroformate, 2‐chloroethyl chloroformate and 2,2,2‐trichloroethyl chloroformate. 2,2,2‐Trichloroethyl chloroformate is the most reactive reagent, and yields a reaction product which can be sensitively detected by GC ECD (detection limit 50 ng/ml, i.e. 25 pg/injection, for C8, C10, and C12 acids).In non‐aqueous media 3‐picoline, N‐methylpiperidine, and dimethylaminopyridine show catalytic activity comparable with that of pyridine and can, therefore, replace it. N‐methylpiperidine is the best basic catalyst in aqueous media (i.e. media containing up to 40 % water).
Comparison of xenon and carbon dioxide as mobile phases in on‐line SFC‐FTIR: Chromatographic and spectroscopic considerations
Authors: Jenkins Timothy J. , Davidson George , Healy Michael A. , Poliakoff Martyn 
Published: May 2005

AbstractSupercritical carbon dioxide and xenon are compared as mobile phases for SFC‐FTIR. Examples are presented illustrating the use of xenon in SFC and it is compared with carbon dioxide for a range of compounds of different polarities. Investigations of the effects of mobile phase temperature and density on infrared spectra measured in supercritical solution are also presented.It has been found that carbon dioxide gives smaller shifts with temperature and density changes than had been reported previously and that carbon dioxide and xenon give rise to remarkably similar effects in almost all circumstances. A comparison of SFC‐FTIR spectra with vapor‐ and condensedphase data is presented and it is shown that such data will require modification to model the effects of the supercritical solvent. The study shows that such modification should be relatively straightforward.
Metal ion capillary zone electrophoresis with direct UV detection: Separation of metal cyanide complexes
Authors: Buchberger Wolfgang , Semenova Olga P. , Timerbaev Andrei R. 
Published: May 2005

AbstractMixtures of cyanide complexes of iron(III), copper(I), iron(II), nickel(II), chromium(III), mercury(II), palladium(II), silver(I), cadmium(II), zinc(II), cobalt(II), and cobalt(III) have been separated by capillary zone electrophoresis using a fused silica capillary and 20 mM phosphate buffers containing 1–2 mM sodium cyanide. The complexes were detected by direct UV absorpticn at 214 nm; detection limits are in the mid ppb range for all metals except cadmium and zinc. The different detectability of various metal cyanide complexes enables the application of the method to the analysis of complex matrices such as cyanide plating bath solutions.
HPLC coupled with ICPMS for the determination of metalloporphyrins in coal extracts
Authors: Pretorius Warren , Foulkes Mike , Ebdon Les , Rowland Steve 
Published: May 2005

AbstractThe HPLC‐ICPMS determination of gallium porphyrins in various coal extracts is described. The HPLC‐ICPMS results are compared with results obtained by HPLC‐UV/VIS. The presence of gallium has been confirmed in all the porphyrin macrocycles.
Cyclodextrin derivatives for the GC separation of racemic mixtures of volatile compounds. Part VI: The influence of the diluting phase on the enantioselectivity of 2,6‐Di‐O‐methyl‐3‐O‐pentyl‐β‐cyclodextrin
Authors: Bicchi Carlo , Artuffo Giuseppe , D'Amato Angela , Manzin Valeria , Galli Anna , Galli Mario 
Published: May 2005

AbstractAs a continuation of previous studies on the use of cyclodextrin derivatives (CD) for the separation of volatile compounds by capillary GC, the influence of diluting phases other than OV‐1701 or OV‐1701‐OH has been investigated.2,6‐Di‐O‐methyl‐3‐O‐pentyl‐β‐cyclodextrin (2,6‐DiMe‐3‐Pe‐β‐CD) was taken as the reference CD derivative, because of the large number of volatile racemates it is able to separate; OV‐1701 or OV‐1701‐OH was chosen as the reference diluting phase.The performance of a column coated with a 0.15 μm film of 10 % 2,6‐DiMe‐3‐Pe‐β‐CD in OV‐1701 was compared with that of analogous columns coated with films of the same thickness containing the same percentage of the CD derivative diluted with stationary phases of different polarity, i.e. PS‐086, PS‐347.5, and OV‐225. Resolution values and separation factors of thirty racemates were used to evaluate the effect of different diluting phases on column performance.
Splitless injection of large volumes of aqueous samples – A basic feasibility study
Authors: Grob Konrad , Fröhlich Dieter 
Published: May 2005

AbstractExperiments with splitless injection of large volumes of aqueous samples by the overflow technique have shown that an organic co‐solvent is necessary to help the packing material (Tenax) retain the liquid. With 25–30% propanol or 15–20% 2‐butoxyethanol, some 800 μl can be injected into a 5 mm i.d. liner. The application of the method is restricted to components eluting above ca 200 °C.
Quantitative determination of fluorine in toothpastes
Authors: Skočir Emil , Pečavar Anica , Krašnja Adolf , Prošek Mirko 
Published: May 2005

AbstractThe quantitative CE analysis of fluorine and monofluorophosphate in toothpastes is described. Separation is performed using a Waters CIA‐Pak chemistry kit with Waters Electro Osmotic Flow Modifiers on a CE instrument from Spectra Physics (Spectra‐phoresis 500) at elevated temperatures up to 40 °C and at a low temperature of 10 °C. The quantitative results and the simplicity are compared for the CE method, the existing standard GC procedure described in the Official Journal of the European Communities, and the procedure employing a fluoride‐ion‐specific electrode.
Analytical scale supercritical fluid fractionation of a low molecular weight, high density polyethylene wax with carbon dioxide
Authors: Via Jim , Braue Cheryl , Taylor Larry T. 
Published: May 2005

AbstractThis paper reports on the use of supercritical carbon dioxide to fractionate a low molecular weight, high density polyethylene into very narrow molecular weight distributions (MWDs). A simple extraction system was developed that allowed relatively trouble free extractions of the polyethylene samples. Fractions were collected at successively higher densities of CO2 at constant temperature and then analyzed by capillary supercritical fluid chromatography (SFC), or high temperature gel permeation chromatography (GPC) and/or differential scanning calorimetry (DSC). Fractionations were performed at three different temperatures (60,80, and 100°C). Higher temperatures were found to yield greater recoveries and higher MWDs at any given density. Reducing the increment between successive extraction steps resulted in polydispersities being reduced to nearly “monodisperse” levels. Total recoveries ranged from 12 to 33% depending on the temperature, and the highest molecular weight fraction extracted by the CO2 was centered around 1500.
On‐line enzymatic reaction, extraction, and chromatography of fatty acids and triglycerides with supercritical carbon dioxide
Authors: Berg Bjørn E. , Hansen Ellen M. , Gjørven Synnøve , Greibrokk Tyge 
Published: May 2005

AbstractSupercritical carbon dioxide can be utilized both as an introduction solvent in capillary SFC and as a reaction medium; both possibilities are illustrated in this study. An off‐line SFE unit was modified for on‐line SFE‐SFC. To facilitate rapid depressurization of the extraction cell and to prevent memory effects, a 6‐port valve was installed at the outlet line of the extraction unit. An increased background signal was obtained when PEEK polymer was used in the construction of the extraction vessel; when stainless steel was used, the blanks improved. The synthesis of methyl esters and butyl esters of fatty acids from triglycerides in edible fat was examined using an immobilized lipase as a catalyst in on‐line SFE‐SFC. As a result of 30 minutes reaction – extraction time, high yields of fatty acid esters were obtained at a pressure of 150 bar and a temperature of 50°C.
Gas chromatographic separation of atropisomeric alkylated and polychlorinated biphenyls using modified cyclodextrins
Authors: König Wilfried A. , Gehrcke Bärbel , Runge Torsten , Wolf Christian 
Published: May 2005

AbstractSelectively alkylated cyclodextrins have been used to resolve the enantiomers of 2,2′ alkylated biphenyls. The configurational stability of 2,2′‐dimethyl and 2,2′‐diethyl biphenyls is insufficient for gas chromatographic separation even at ambient temperature. 2‐Isopropyl‐2′‐t‐butyl‐ and 2,2′‐di‐t‐butylbiphenyl are configurationally stable under the conditions applied, whereas 2,2′‐diisopropyl‐ and 2,2′‐bis(trifluoromethyl)biphenyl show temperature‐dependent interconversion of the enantiomers during chromatography. The gas chromatographic separation of the enantiomers of some ortho trichlorinated biphenyls carrying 4, 5, and 6 chlorine substituents has been demonstrated for the first time.