bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a new pyrolyzer for thermal desorption and/or pyrolysis gas chromatography of polymeric materials
Authors: Watanabe Chuichi , Teraishi Kuniko , Tsuge Shin , Ohtani Hajime , Hashimoto Keiji
Published: May 2005

A new vertical microfurnace‐type pyrolyzer for thermal desorption and/or pyrolysis‐gas chromatography has been developed. The pyrolyzer consists of two independent temperature‐controlled ovens.

Initially, in the desorption process, a sample cup containing the polymeric sample of interest is inserted into an oven at 300°C; the sample is then re‐positioned at the upper part of the pyrolyzer where the temperature is maintained at room temperature. The resulting vaporized components such as residual solvents and additives give a desorption chromatogram. The relative peak intensities of desorbed plasticizers in acrylonitrile butadiene‐rubber gave a relative standard deviation (RSD) of less than 2%.

Subsequently, pyrolysis of the remaining polymer is conducted by dropping the sample cup into the second, pyrolyzing, oven at 55°C; at this stage the pyrogram is recorded.

The resulting two chromatograms of desorbed components and pyrolysis products make it easier to characterize the polymer formulation than the complicated pyrogram obtained by an ordinary, single‐step pyrolysis.
The production of artifacts during preparation of fatty acid methyl esters from fish oils, food products and pathological samples
Authors: Moffat Colin F. , McGill Alister S. , Anderson Robert S.
Published: May 2005

Methyl esters were synthesized from lipid extracted by a modified Bligh and Dyer technique. The lipid was saponified and the free fatty acids methylated using boron trifluoride in methanol. Butylated hydroxytoluene (BHT; 2,6‐di‐tert‐butyl‐4‐methylphenol) was added to the initial sample and to the extracted lipid prior to methyl ester synthesis.

Under these conditions, the BHT was derivatized to a range of compounds, some of which can result in misinterpretation of the GC trace.

Three components have been characterized by mass spectroscopy. Two of these, which eluted slightly before 16:0 on a polar column, were shown to be 2,6‐di‐tert‐butyl‐4‐methoxyphenol and 2,6‐di‐tert‐butyl‐4‐methoxy‐methylphenol. The third component, which coeluted with 15:0 on the same column, is 2,6‐di‐tert‐butyl‐4‐methoxy‐5‐hydroxyphenol.
Investigation of low mass oligomers and polymer additives from plastics. Part II: Application to polyolefin soxhlet extracts
Authors: Dilettato Dominique , Arpino Patrick J. , Nguyen Koa , Bruchet Auguste
Published: May 2005

Polyolefin Soxhlet extracts have been investigated by capillary SFC using flame ionization detection. Separation and detection of every polymer additive (antioxidants, antistatic agents, etc.) present in the plastic were possible, sometimes in a single CSFC run. Identification of coextracted low mass oligomers and certain of the alteration products of Irganox 1010 was confirmed by GC‐MS. New methods are presented for the determination of reacted and remaining calcium stearate, used in plastics both as a stabilizer and a lubricant.
Optimization of dynamic headspace sampling for the analysis of trace volatile components of grape juice: Use of a PTV injector for intermediate trapping
Authors: Tabera Javier , Reglero Guillermo , Herraiz Marta , Blanch Gracia P.
Published: May 2005

The use of a programmed temperature vaporizing (PTV) injector has been evaluated for the on‐line concentration and injection of trace organic compounds either sampled from the head‐space above grape juices or purged from solution.

The Simplex method was used to improve the sensitivity of the method by optimization of the experimental conditions.
Aalysis of the fatty acid composition of the lipid classes in human blood serum under normal diet and when supplemented with fish oil
Authors: Liebich H. M. , Jakober B. , Wirth C. , Pukrop A. , Eggstein M.
Published: May 2005

Total lipids have been extracted from human serum with chloroform–methanol 2:1 (v/v) and separated into individual classes by TLC. After transesterification the fatty acid methyl esters were analyzed by capillary gas chromatography on an FFAP column. The quantitation of ω‐3 fatty acids has been performed using internal and external standards. Internal lipid standards for each lipid class were carried throughout the entire analytical procedure. Under normal diet eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are incorporated into the lipid classes to different extents: cholesterol esters; EPA, 6.5 ± 1.9 γ/ml serum; DHA, 4.3 ± 1.9 μg/ml: phospholipids; EPA, 5.9 ± 2.7 μg/ml; DHA, 31.8 ± 8.1 μg/ml. Fish oil supplementation leads to a 4 to 6‐fold rise in EPA and to an approximately 2‐fold rise in DHA.
Micropacked capillary nucleic acid analysis
Authors: Remcho Vincent T. , McNair Harold M.
Published: May 2005

Nucleic acid compositional analysis is discussed, followed by a brief review of the current state of the technology applied in which the benefits and limitations of current methodology are enumerated. An alternative method is presented, namely the use of a micropacked capillary ion exchange column to separate nucleoside monophosphates via an anion exchange mechanism. The separated nucleotides are then quantitated by means of post‐column photodiode‐array detection. The use of a photodiode array also enables the verification of peak identity and purity by acquisition of UV spectra at any point in the separation. The technique has applications in the compositional analysis of both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Gas chromatographic enantiomer separation of agrochemicals using modified cyclodextrins
Authors: König Wilfried A. , Icheln Detlef , Runge Torsten , Pfaffenberger Bernd , Ludwig Peter , Hühnerfuss Heinrich
Published: May 2005

The enantiomers of phenoxypropionic acid type herbicides have been resolved by capillary gas chromatography employing modified cyclodextrins as chiral stationary phases. Excellent separations were obtained with columns containing a 1:1 mixture of per‐O‐pentylated and per‐O‐methylated γ‐cyclodextrin.

The enantiomers of the methyl esters of mecoprop and dichlorprop were also resolved on octakis(3‐O‐butyryl‐2,6‐di‐O‐pentyl)‐γ‐cyclodextrin. On this phase the order of elution of the enantiomers was temperature‐dependent, the elution order being reversed as the temperature passed through the isoenantioselective temperature. This is the first time such behavior has been observed with cyclodextrin derivatives.

The enantiomers of the polychlorinated polycyclic pesticides cis‐ and trans‐chlordane, oxychlordane, heptachlor, heptachlorepoxide, and three chiral organophosphorus pesticides could be resolved using selectively derivatized cyclodextrin derivatives.
Organochlorine residue analysis of commercial milks by capillary gas chromatography
Authors: Redondo M. Jesús , Picó Yolanda , Server‐Carrió Juan , Manñes Jorge , Font Guilermina
Published: May 2005

The determination of organochlorine pesticides and polychlorinated biphenyls in milks requires the use of efficient extraction methods. A rapid procedure has been developed, based on extraction of organochlorine residues from milk on to octadecylsilica solid phase extraction cartridges and elution with hexane. The addition of different organic solvents to the milk before solid phase extraction has been studied. The use of methanol to disrupt the fat globules enables almost complete recovery of the residues with minimum extraction of fatty substances.

Recovery experiments were performed for eighteen compounds present at ppb levels in whole, two per cent, and skimmed milks. The average recoveries of the compounds from two per cent and skimmed milks were 73–84%; values for whole milk were lower. The residues were determined by gas chromatography using two kinds of capillary column (non‐polar and semi‐polar) and electron capture detection. The procedure shows low lipid carry over, and extraneous interferences are minimal.

The method has been applied to the detection of organochlorine pesticides and nine individual polychlorinated biphenyls in commercial milks. The results obtained demonstrated the presence of very low levels of organochlorine residues in the commercial milks analyzed.
The enantioselectivity of modified cyclodextrins: Studies on interaction mechanisms
Authors: Venema Arnold , Henderiks Harmanna , v. Geest Renie
Published: May 2005

The separation of enantiomers of rather simple molecules, such as alkanes and alkanoic acid esters substituted at the 2‐position, has been investigated on alkylated β‐cyclodextrin stationary phases. By observing the effect of varying the substrate and the cyclodextrin alkylating agent it has been possible to propose a mechanism for the separation. The most important factors seem to be hydrophobic interactions and the ability of the cyclodextrin to change its conformation to accept the guest molecule.
The effect of treating air samples with magnesium perchlorate for water removal during analysis for non‐methane hydrocarbons
Authors: Doskey Paul V.
Published: May 2005

A comparison has been made between two cryogenic preconcentration ‐ high resolution gas chromatography techniques for the analysis of non‐methane hydrocarbons in ambient air, one involving treatment of air samples with magnesium perchlorate to remove water, the other involving analysis without treatment. Recoveries of C1‐, C2‐, and C3‐substituted benzenes in treated samples were 80%, 50%, and 50%, respectively. Incomplete recovery of C7‐C9 n‐1‐olefins was also observed. C2‐C8 hydrocarbons and C2‐C6 n‐1‐olefins were recovered with greater than 90% efficiency. Analyses of certified audit samples containing a mixture of C2‐C8 aliphatic and aromatic hydrocarbons at the 20 ppbv level in humidified zero‐grade air indicated that the accuracy of the technique for untreated air samples was approximately 90%. The use of magnesium perchlorate for water removal cannot be recommended for the analysis of non‐methane hydrocarbons in ambient air.
Analysis of volatile aromatic compounds in gasoline‐contaminated ground water samples by static headspace sampling and high speed gas chromatography
Authors: Wang Suya , Stuart James D. , Ke Huiqiong , Levine Steven P.
Published: May 2005

A 15 second, high speed, gas chromatographic determination has been performed on the volatile aromatic compounds in gasoline‐contaminated ground water following manual, static headspace sampling. Retention time reproducibility of the seven peaks studied ranged from 0.25 to 0.67 per cent (average relative standard deviation). Excellent linear correlations were obtained for plots of either peak height or peak area against the concentration of the compounds. Comparison was made between the results obtained from the analysis of three replicate samples of gasoline‐contaminated ground water by the high speed GC, by two field‐portable GCs, and by a laboratorybased GC. It is worthy of note that all the high speed GC analyses required for this study were accomplished in one day.
Determination of the ionization constants of weak electrolytes by capillary zone electrophoresis
Authors: Cai Jianyi , Smith Joel Tim , Rassi Ziad El
Published: May 2005

Capillary zone electrophoresis in untreated fused silica capillaries has proved suitable for the determination of the ionization constants of weak electrolytes. Several fundamental equations relating the electrophoretic mobilities of ionized solutes to hydronium ion concentrations in the running electrolyte have been verified experimentally. The observed dependence of the electrophoretic mobilities of weak bases and ampholytes on the pH of the electrolyte showed good agreement with predicted behavior. The pKa values calculated from electrophoretic mobility data obtained by capillary zone electrophoresis were reasonably close to those reported in the literature.
Factors affecting C:H and C:N ratios determined by gas chromatography coupled with atomic emission detection
Authors: Pedersen‐Bjergaard Stig , Asp Tone Normann , Greibrokk Tyge
Published: May 2005

An atomic emission detector has been evaluated for the estimation of C:H and C:N ratios of compounds eluted in gas chromatography. When C:H and C:N ratios were estimated using external reference compounds, the greatest accuracy was obtained when the quantity of the reference compound was similar to that of the analyte of interest.

The accuracy of the C:H and C:N ratios determined was also affected by the molecular structure of the reference compound. C:H ratios of the greatest accuracy were obtained by using reference compounds having structures similar or close to those of the compound of interest; this was not always so for C:N ratios.
Determination of organochlorine pesticide residues by solid phase extraction and dual‐column HRGC
Authors: Torreti Luigi , Simonelia Anselmo , Dossena Angelo , Torreti Emilio
Published: May 2005

Organochlorine pesticide residues have been extracted from samples of animal feed by a solid phase extraction clean‐up procedure using an octadecyl‐bonded column. The proposed method gave recoveries ranging from 70 to 100 % for ppb levels of the fifteeen pesticides studied. Analytes were identified by dual‐column capillary gas chromatography employing DB‐1 and DB‐1701 columns in parallel; identities were confirmed by calculation of retention indexes with the cubic spline interpolation method.
Linear temperature programmed retention indices of gasoline range hydrocarbons and chlorinated hydrocarbons on cross‐linked polydimethylsiloxane
Authors: White Curt M. , Hackett Joe , Anderson Richard R. , Kail Sally , Spock Paul S.
Published: May 2005

This paper describes the experimentally determined linear temperature programmed gas chromatographic retention behavior of hundreds of gasoline range hydrocarbons and chlorinated hydrocarbons on a cross‐linked 100% polydimethylsiloxane stationary phase. The retention indices of additional compounds which were not available as pure standards were measured in a synthetic gasoline after they had been positively identified by matching mass and infrared spectra.

The experimentally determined retention information has been used to estimate the retention indices of additional compounds by extrapolation or interpolation of plots of carbon number against retention index of homologs.

Isothermally determined Kovats retention indices of compounds measured on 100 % polydimethylsiloxane have been taken from the literature and converted to linear temperature programmed retention indices using the method of Guan et al [11]. For many of these compounds, an experimentally determined linear temperature programmed retention index was measured: agreement between experimental and converted values was excellent.

In total, retention indices are presented for 480 compounds, including all possible alkylbenzenes containing ten or fewer carbon atoms, and over 150 monoenes and dienes. The effect of column pressure and the average linear velocity of the helium carrier gas on retention index and order of elution is described and discussed.
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

The 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

Static 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

Microcolumn 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

New 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

The 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

Lubricating 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

Nine 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

This 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

Element‐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

Polyvinylalcohols (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

Sample 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

A 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

Solid 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

A 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

Fatty 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

Supercritical 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

Mixtures 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

The 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

As 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

Experiments 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

The 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

This 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

Supercritical 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

Selectively 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.
LC‐amperometric determination of tert‐butylcatechol in N‐methyl‐2‐pyrrolidone stream containing polar and nonpolar impurities
Authors: Barman Bhajendra N.
Published: May 2005

Amperometric detection is shown to be highly selective and sensitive for the determination of tert‐butylcatechol (TBC) added as an antioxidant in the circulating N‐methyl‐2‐pyrrolidone (NMP) used for the purification of 1,3‐butadiene by extractive distillation. The separation of TBC from numerous polar and nonpolar species present in the analyte is achieved on a 5‐cm reversed‐phase C‐18 column using acetonitrile‐water gradient conditions, both solvent components containing tetrabutyl ammonium dihydrogen phosphate as the amphiphilic modifier. The separation process is optimized for the resolution of TBC from nonpolar hydrocarbons as well as polar compounds, and a complete elution of all species from the column. An applied potential of 0.6 V relative to the Ag/AgCI electrode is found to provide an optimum sensitivity by the amperometric detector. It is also shown that the hydrocarbon content in NMP can be monitored simultaneously by coupling a spectrophotometric detector in series.
The analysis of chlorinated dibenzofurans in municipal fly ash: Supercritical fluid extraction vs Soxhlet
Authors: Onuska Francis I. , Terry Ken A. , Wilkinson R. J.
Published: May 2005

A multiresidue supercritical fluid extraction procedure for chlorinated dibenzofurans (PCDFs) has been optimized as an efficient method for the determination of these compounds in fly ash samples. The results were compared with those obtained by Soxhlet extraction. Extracts from the two procedures were analyzed by gas chromatography–mass spectrometry (HRGC–MS) Statistical analysis of the results confirmed that supercritical fluid extraction provides data with a relative standard deviation of less than 10% while Soxhlet extraction data show a much greater spread.
Determination of pentane in human breath by gas chromatography
Authors: Moodie Ian M. , Labadarios Demetre
Published: May 2005

A new procedure, requiring expired sample volumes of approximately 2L, has been developed for the quantitative determination of n‐pentane in human breath. The methodology capitalizes on the superior resolving power and separating efficiency of the open tubular capillary column and incorporates an effective prechromatographic cryofocusing technique. Molecular sieve is used to simultaneously remove moisture and carbon dioxide from breath samples which are “spiked” with an internal standard to optimize the validity of analysis. Reproducible data for both internal standard spiking (CV = 5.8%) and sample n‐pentane level (CV = 3.2%) have been obtained, together with a mean recovery of 104%. Preliminary data show n‐pentane levels in normal female subjects (n = 10) to range from 0.62 to 3.16 nmole/L (mean 1.76 nmole/L) and in males (n = 10) from 3.20 to 8.76 nmole/L (mean 5.66 nmole/L).
Capillary supercritical fluid chromatography of limonoids
Authors: Raynor Mark W. , Roberts Sianne L. , Mulholland Dulcie A.
Published: May 2005

Capillary supercritical fluid chromatography (SFC) with carbon dioxide as the mobile phase has been used to separate a mixture of limonoid standards. Chromatographic conditions were optimized to enable analysis of plant extracts. The seed of Aphanamixis polystacha (Meliaceae) and the stem bark of Harpephyllum caffrum (Anacardiaceae) were extracted with hexane and the extracts were analyzed by SFC to demonstrate the potential of the technique as a screening tool. SFC analysis indicated the presence of limonoids in the hexane extract of the bark of Entandrophragma delevoyii (Meliaceae). One limonoid and two protolimonoids isolated from the extract were separated by SFC.
On‐line high performance liquid chromatography — multidimensional gas chromatography and its application to the determination of stilbene hormones in corned beef
Authors: Chappell Colin G. , Creaser Colin S. , Shepherd Martin J.
Published: May 2005

The combination of high performance liquid chromatography interfaced on‐line with multidimensional gas chromatography (HPLC–GC–GC) is described. The HPLC column was interfaced to the GC via an on column interface, with automated pneumatic control of solvent evaporation and GC column switching. Cryogenic cold trapping was used for analyte focusing at the head of the first, non‐polar GC capillary column and optionally at the head of the second, polar column. The determination of stilbene hormones in corned beef as their methylated derivatives by flame ionization detection is described.
Analysis of free and esterified sterols in vegetable oil methyl esters by capillary GC
Authors: Plank Christina , Lorbeer Eberhard
Published: May 2005

The introduction of quality standards for vegetable oil methyl esters is gaining in importance due to their increased use as diesel fuel substitutes and as technical products. Free and esterified sterols, the main constituents of the unsaponifiable matter in vegetable oils, are recovered in vegetable oil methyl esters and may influence the technical properties of vegetable oil methyl ester products. A rapid gas chromatographic method for the qualitative and quantitative determination of free and esterified sterols in vegetable oil methyl esters has therefore been developed.

The concentration of the free sterols as well as their qualitative and quantitative composition and the concentration of the sterol esters have been determined in rape seed oil methyl ester samples by GC–FID. Prior to analysis, the free sterols were silylated with N,O‐bis(trimethylsilyl)trifluoroacetamide with 1% of trimethylchlorosilane; betulinol was used as an internal standard. Calibration was performed by analysis of standard solutions containing β‐sitosterol, cholesteryl stearate, and betulinol. The reproducibility of the quantitative results has been evaluated by repeated injections of the same test solution and by repeated complete analysis of the same sample.
Investigation into the GC separation of enantiomers on a trifluoroacetylated cyclodextrin. Part II: Effect of derivatization on stereoselectivity towards alcohols
Authors: Smith Ian D. , Simpson Colin F.
Published: May 2005

Two acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6‐di‐O‐n‐pentyl‐3‐O‐trifluoroacetyl)‐ γ‐cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2‐ and 3‐hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four‐carbon chain attached to the stereogenic center. For longer‐chain fluoroacyl derivative groups stereoselectivity was higher for the 2‐ and 3‐hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl‐branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole–dipole contribution and some form of steric component, depending upon the shape and/or size of the solute.
Purification and analysis of partially alkylated cyclodextrins by liquid and gas chromatography
Authors: Deege Alfred , Husmann Heribert , Hübinger Eduard , Kobor Frank , Schomburg Gerhard
Published: May 2005

Complex mixtures of partially alkylated cyclodextrins can be analyzed by both HPLC and high temperature capillary GC. Because of the limited efficiency of LC, suitable analytical and preparative separations can be achieved only with systems of carefully optimized selectivity. Using LC it has been possible to isolate and purify single cyclodextrin species from very complex mixtures of components which contain unreacted hydroxyl groups in addition to the alkoxy groups. Analysis of the reaction mixtures and of fractions taken from LC separations can be performed with advantage by high resolution capillary GC at high temperatures between 300 and 400 °C. The thermal stability of partially alkylated cyclodextrins in high temperature GC is considerably increased by trimethylsilylation of the free hydroxyl groups. Fast atom bombardment mass spectrometry and proton NMR were used to identify species isolated from the preparative LC separations.