bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of radicals spin‐trapped in autoxidized linoleic acids: A high performance liquid chromatography and electron spin resonance study
Authors: Evans J. C. , Rao K. R. N. , Jackson S. K. , Rowlands C. C. , Barratt M. D.
Published: May 2005

Radicals generated in linoleic acid and deuterated linoleic acid have been trapped by the spin trap 2‐methyl‐2‐nitroso‐propane (MNP) and identified by electron spin resonance (ESR) and ENDOR spectroscopy. The formation of two distinct secondary alkyl radical adducts (one conjugated, the other non‐conjugated, as shown by their UV absorption spectra) was demonstrated by 11, 11‐dideuterio‐9‐cis‐12‐cis‐linoleic acid using HPLC and ESR spectroscopy.
Static coating of capillary columns by means of liquefied gases
Authors: Janák K. , Kahle V. , Tesařík K. , Horká M.
Published: May 2005

The technique of spontaneous coating of capillary columns employing liquefied butane and ethylene chloride as solvents of the stationary phase is described. These solvents and their mixtures are suitable for apolar and medium‐polar stationary phases. The dependence of coating time on coating temperature and on the composition of the mixture of solvents was observed. It was found that the coating efficiency decreases with increasing coating speed.
Application of chemometrics to the classification of orange essence oil varieties by GLC
Authors: Mayfield H. T. , Bertsch W. , Mar T. , Staroscik J. A.
Published: May 2005

Orange essence oils of the Navel and Valencia variety were analyzed by GC and GC/MS using two parallel capillary columns of different selectivity. Data were normalized, converted into a computer compatible format, and transferred via an asynchronous communications interface to a mainframe computer for statistical treatment, using the chemometrics software package ARTHUR. After suitable preprocessing of the raw data, reliable classification was possible. It appears that four substances which are present in both varieties can be used for that purpose.
Fused‐silica microparticulate packed column HPLC‐split flow gradient elution
Authors: Yang F. J.
Published: May 2005

Fused‐silica microparticulate packed columns are demonstrated to have equal or better separation efficiency and resolving power than conventional 4.6 mm i.d. packed columns. While neither separation efficiency nor resolving power is an inherent consequence of capillary column use, there re potential advantages of using fused‐silica capillary columns, particularly when microparticulate particles of 1 to 5 üm are used in the gradient elution mode. Gradient elution techniques compatible with flow rates below 30 μL/min are discussed. Spli‐flow gradient elution of twenty PTH amino acids using 10 and 40 cm × 0.54 mm i.d. columns packed with 4 μm Micro‐Pak PTH‐AA particles is demonstrated. Detection limits of 0.1–0.3 picomoles are meaured for PTH amino acids and 0.01–0.02 picomoles for tricyclic antidepressant drugs.
Capillary supercritical fluid chromatography‐mass spectrometry
Authors: Wright B. W. , Kalinoski H. T. , Udseth H. R. , Smith R. D.
Published: May 2005

Capillary supercritical fluid chromatography and its combination with mass spectrometry (SFC‐MS) is an important analytical methodology for the analysis of thermally labile and high molecular weight compounds. The mass spectrometer provides sensitive and highly selective detection for the chromatographic effluent. The same physical‐chemical properties of supercritical fluids that provide important chromatographic advantages are also important for the transport and gas phase introduction of analyte molecules into the mass spectrometer. The low mobile phase flow rates of small diameter (< 100 μm i.d.) capillary columns allow the total chromatographic effluent to be introduced with conventional, but often slightly modified, ion source configurations for quadrupole mass spectrometers with either electron impact (EI) or chemical ionization (CI) detection. The full range of CI reagents can also be used to obtain additional selectivity and complementary structural data. The instrumentation and operating parameters for capillary SFC‐MS methods are described. The applicability and usefulness of various SFC‐MS analysis methods are demonstrated using a variety of samples.
Open tubular column supercritical fluid chromatography/mass spectrometry on a benchtop mass spectrometer
Authors: Lee E. D. , Henion J. D.
Published: May 2005

A benchtop SFC/MS system is described which utilizes supercritical carbon dioxide in a 50 micron diameter open tubular column interfaced directly to an unchanged commercially available benchtop capillary GC/MS system equipped with a chemical ionization (CI) source. A small amount of methane reagent gas was admitted co‐axially to a capillary restrictor at the exit of the capillary chromatographic column. This make‐up gas served as the CI reagent gas and appeared to optimize the sensitivity of the system while providing abundant (M+1) ions for the analytes investigated in this study. Good chromatographic intergrity was obtained for the GC/MS test compound, decafluorotriphenylphosphine (DFTPP), but the capillary restrictor appeared to cause some tailing of the ion current profiles resulting from low nanogram levels of caffeine and some fatty acid esters. Improvements in the SFC/MS capillary restrictor interface and the pumping system of the benchtop GC/MS system should increase the capability of this system for future applications.
Analysis of commercial dyes by capillary column supercritical fluid chromatography
Authors: Jackson Wm. P. , Later D. W.
Published: May 2005

High resolution separations of selected commercial azo, aniline, and anthraquinone dyes by capillary column supercritical fluid chromatography (SFC) are demonstrated. Supercritical n‐pentane was used as a mobile phase and provided efficient separations of multi‐functional, polar disperse dyes with molecular weights up to approximately 700 daltons.
Separation of oligo‐ and polysaccharides by capillary supercritical fluid chromatography
Authors: Chester T. L. , Innis D. P.
Published: May 2005

Direct analysis of polar solutes by supercritical fluid chromatography (SFC) has been somewhat limited because the mobile phases in common use are all relatively nonpolar. Derivatization is demonstrated as a viable means for facilitating the SFC separation of sugars. Oligo‐ and polysaccharides containing up to 18 glucose units are completely resolved by capillary SFC.
Supercritical fluid injection of high‐molecular‐weight polycyclic aromatic compounds in capillary supercritical fluid chromatography
Authors: Jackson W. P. , Markides K. E. , Lee M. L.
Published: May 2005

A sample introduction system for capillary supercritical fluid chromatography, which allows the dissolution of the sample in the supercritical mobile phase before being introduced into the column, was constructed and evaluated. Supercritical n‐pentane was shown to solvate high‐molecular‐weight polycyclic aromatic compounds that could not be solvated using typical liquid solvents. In addition, split injection of a supercritical fluid solution was found to be more reproducible than split injections of a liquid solution. The potential of such an injection system was demonstrated, although further developments are needed in order to make the technique of practically utility.
Large diameter open tubular columns in gas chromatographic analysis
Authors: Mehran M. F.
Published: May 2005

Large diameter open tubular columns provide the packed column chromatographer with a simple route to higher resolution gas chromatography. They can be operated in a high‐flow (lower resolution) mode that permits their direct substitution for a packed column, or they can be operated in a low‐flow (higher resolution) mode that maximizes separation at the cost of longer analysis times. Inlet design and column installation can influence both the chromatographic results and quantiative reliability. Make‐up gas is not required in the high‐flow mode, and its benefits in the low‐flow mode are restricted to enhanced detector sensitivity, provided the outlet end of the column resides in the detector jet (FID). The columns seem fully compatible with all common modes of detection.
Electron capture detector response to low electron affinity aromatic hydrocarbons using positive ion stabilization and alkyl chloride sensitization
Authors: Valkenburg C. A. , Knighton W. B. , Grimsrud E. P.
Published: May 2005

The electron capture detector (ECD) response to numerous aromatic hydrocarbons of low electron affinity (EA) is shown to be detrimentally affected by two processes which compete with and typically overwhelm the electron capture reactions of these molecules. It is shown that the effects of these two undesired reactions can be eliminated by the permanent addition of trimethylamine and one of several alkyl monochlorides to the detector make‐up gas. These modifications of the detector gas result in greatly increased sensitivity, increased linearity, and increased reproducibility of response. A kinetic model for the ECD responses of low EA resonance capture molecules is developed which appears to explain these improvements.
Fast high‐performance liquid chromatographic determination of R(+)[(5,6‐dichloro‐2,3,9,9a‐tetrahydro‐3‐oxo‐9a‐propyl‐1‐H‐fluoren‐7‐yl)oxy]acetic acid in human plasma and urine
Authors: Hsieh J. Y‐K. , Maglietto B. K. , Bayne W. F.
Published: May 2005

A simple and rapid high‐performance liquid chromatographic method for the determination of R[(5,6‐Dichloro‐2,3,9,9a‐tetrahydro‐3‐oxo‐9a‐propyl‐1‐H‐fluoren‐7‐yl)oxy]acetic acid (I) in human plasma and urine is described. The method utilizes Bond‐Elut® cartridge facilitate the drug extraction. Analysis is performed on a short reversed‐phase column with a mobile phase consisting of acetonitrile and phosphate buffer and quantification is carried out by ultraviolet detection with a wave‐length set at 340 nm. The method is linear and reproducible for both plasma and urine analyses (0.25–50) μg/mL) with the detection limit of 125 ng/mL of plasma and urine. Plasma and urine concentrations of / at selected time intervals following I.V. administration of single rising doses are presented.
Immobilized very thick film PS‐255 capillaries in solvent trace analysis, effect of sample size on solute retention
Authors: Lakszner K. , Szepesy L.
Published: May 2005

The purpose of this work was to assess the suitability of nonpolar very thick‐film capillaries for the analysis of organic solvents in water. We investigated the major factors influencing the analytical results, namely: film‐thickness; amount of water injected; and analysis temperature.
Utilization of the Sadtler standard RI system in micropollution analyses
Authors: Weber L.
Published: May 2005

During the development of a GC retention index library very rigorous standard parameters were used in the SADTLER laboratories. Because most chromatographers presumably have their “favourite” and well‐proven columns a study has been carried out on how to make use of them for standard index generation. Variables such as column geometry, split ratio, and film thickness were examined and the calculated indices were compared to some “basic” values. Splitless and cool on‐column injection techniques were also investigated and comparable temperature programming indices have been obtained. Finally, standard index values of 53 volatile halogenated hydrocarbons measured on very thick‐film bonded fused silica capillary columns are tabulated.
Deactivation of small diameter fused silica capillary columns with organosilicon hydrides
Authors: Woolley C. L. , Markides K. E. , Lee M. L. , Bartle K. D.
Published: May 2005

Small diameter fused silica capillary columns (50–75 μm i.d.) were deactivated at relatively low temperatures (250–300°C) with a mixture of polymethylhydrosiloxanes and several lowmolecular‐weight organosilicon hydrides. Reproducible surface deactivations of highest quality were achieved with the polymethylhydrosiloxane (PMHS) reagent. Deactivations performed with PMHS via dynamic coating with neat or diluted reagent were evaluated by gas chromatography. Deactivations achieved with organosiloxane mono‐, tri‐, and tetrahydrides were also evaluated and compared. Low‐molecular‐weight organosilicon hydride deactivations were less time consuming and required lower head pressures for filling and coating columns with the reagent. Critical surface tensions of capillary surfaces modified with PMHS and the low‐molecular‐weight organosilicon hydrides gave support to the dehydrocondensation reaction between silica surface silanols and silyhydride bonds of the reagents. Slopes from Zisman plots indicated that coverage of the surface ranged from highest for the polymer (PMHS) to lowest for the monomers (TMS and PMDS). Efficiency measurements showed the influence that surface modification had on the uniformity and stability of the coated capillary columns. Well‐deactivated capillary columns permitted the chromatography of polar solutes using supercritical carbon dioxide as mobile phase.
Analysis of dinitrofluoranthenes by high resolution capillary gas chromatography/mass spectrometry
Authors: Ramdahl Th. , Arey J. , Zielinska B. , Atkinson R. , Winer A. M.
Published: May 2005

This paper reports the retention indices of eighteen of the possible twenty‐five dinitrofluoranthene isomers.
Single derivatives for GC‐MS assay of reducing sugars and selective detection by the nitrogen‐phosphorus detector (NPD)
Authors: das Neves H. J. Chaves , Riscado A. M. V. , Frank H.
Published: May 2005

Reduction of sugar methoximes with sodium cyanoborohydride followed by permethylation with CH3SOCH2−/ICH3 affords the corresponding deoxy(methylmethoxylamino)alditol O‐methyl ethers, which are amenable to capillary gas chromatography. Derivatization proceeds under mild conditions with high yields. Only a single derivative is formed for each reducing sugar. All aldose derivatives can be separated in a single chromatographic run on glass capillaries coated with Carbowax 20 M or Superox 0.1. Good linearity was found. The introduction of the nitrogen atom in the sugar molecule makes these derivatives suitable for selective detection by the NPD. The El‐mass spectra contain intense characteristics ions at m/z 74 for aldoses and at m/z 280 for reducing disaccharides, together with a (M ‐ 15)+ion. These fragments are very suitable for highly sensitive GC‐MS analysis by selective single ion monitoring.
Characterization and determination of PCB isomers by high resolution gas chromatography and HRGC/mass spectrometry
Authors: Onuska F. I. , Terry K. A.
Published: May 2005

An integrated analytical procedure for polychlorinated biphenyl (PCB) multiresidues in environmental samples has been developed and applied to well‐characterized samples. PCB residues are characterized and quantified using wall coated open tubular column (WCOT) gas chromatography or HRGC/MS‐selected ion monitoring. An automated data system based on a Spectra Physics SP‐4200 computing integrator is used to select and quantitate peaks of individual congeners and homolog groups. This procedure consistently yields results with a reproducibility within 3 percent for HRGC‐ECD and 3.7 percent for HRGC/MS‐SIM technique respectively.
Fused silica capillary deactivation with D4 in the presence of oxygen
Authors: Xu B. , Vermeulen N. P. E.
Published: May 2005

A new, simple procedure to deactivate fused silica capillaries without hydrothermal treatment is proposed. Based on high temperature reactions of octamethylcyclotetrasiloxane (D4) in the presence of oxygen, this procedure results, upon coating with dimethylsilicone (SE‐30), in columns which give almost symmetric peaks for as little as 150 pg of critical compounds, such as decylamine, thereby demonstrating very high inertness. A mechanism of the deactivation procedure, which, in contrast to previously developed procedures, is based on thermal reactions under aerobic conditions, is proposed.
Rapid analysis of hydrocarbons and inert gases by a multidimensional gas chromatograph
Authors: Tani H. , Furuno M.
Published: May 2005

A combination of a pressure switching system with multiple columns and photoionization detectors makes possible rapid analysis of a mixture of inorganic gases and hydrocarbons. Hydrocarbons are separated by a narrow bore capillary column. An alumina PLOT column is used for the separation of lower molecular weight hydrocarbons, especially C4 isomers, while a combination of a micro‐packed column with Porapak N and a PLOT capillary column with Molecular Sieve 5A is used for the fast separation of inorganic gases. A photoionization detector is a powerful additional tool for organic gas analysis.
Advantage of the universal equation over the linear equation for the calculation of retention parameters of homologous series in capillary chromatography
Authors: Svetlova N. I. , Samusenko A. L. , Golovnya R. V.
Published: May 2005

A procedure is suggested for preparation of reproducible and stable galss capillary Apiezon LH+KF columns for the determination of organic compounds containing different functional groups. The advantage of the universal equation over the linear equation for calculation of retention indices for any homologs, including the first members of the series, is shown using the following five homologous series as examples: fatty acid methyl esters, methyl ketones, secondary and tertiary aliphatic amines, and N‐alkyl piperidines. The accuracy of the calculation enables the universal equation to be used in computer‐assisted identification.
Behavior of heavy solutes on a precolumn in on‐column gas chromatography
Authors: Takayama Y. , Sumiya E.
Published: May 2005

The behavior of heavy solutes present in a sample injected on the precolumn has not been clarified in on‐column injection onto gas chromatograph having a capillary column coupled to an uncoated precolumn in an oven. To investigate this point, an on‐column gas chromatograph has been developed which is constructed with a heatable precolumn outside the oven. Some experiments were carried out in order to evaluate the performance. As a result, it was found that heavy solutes reach the first part of the main capillary column after the solvent has gone, resulting in sharp peaks without solvent effects. The reason why sharp peaks appear for the heavy solutes is also discussed. The cold‐trapping effect has been shown to play an important role in narrowing the band width of the heavy solutes. Some of the advantages of the gas chromatograph developed are also presented.
Measurement of equilin and estrone in human plasma by capillary gas chromatography‐negative ion chemical ionization mass spectrometry
Authors: Robinson P. R. , Jones M. D. , Maddock J.
Published: May 2005

A procedure is described for the analysis of the estrogens equilin and estrone in human plasma following oral administration of conjugated estrogen preparations. After enzymatic hydrolysis of the sulfate conjugates, plasma proteins are precipitated with methanol and the estrogens extracted into ethyl acetate. Derivatization with the reagent flophemesylamine converts equilin and estrone into volatile pentafluorophenyldimethylsilyl ethers ideally suited to capillary gas chromatography‐negative ion chemical ionization mass spectrometry. Using a 15 meter dimethyl silicone bonded phase fused silica capillary column separation of the estrone and equilin derivatives is achieved within 9 minutes. Selected ion monitoring of the intense negative molecular ions enables levels of 1 ng.ml−1 to be measured with coefficients of variation of 9.3 % and 14.2 % for estrone and equilin respectively. Plasma levels of the compounds are reported in two male volunteers up to 24 hours after dosing with 5 milligrams of Premarin™. (™ Ayerst Laboratories Inc., New York, USA.).
Determination of residual monomers in acrylate dispersions by gas chromatography
Authors: Stoev G. , Angelova M.
Published: May 2005

The content of residual monomers is one of the most important characteristics of polymer dispersions. As a result of the similar physicochemical parameters of ethyl acrylate and methyl methacrylate, it is very difficult to determine the residual monomers in acrylate dispersions obtained by emulsion polymerization of both monomers. Gas chromatography with capillary columns, however, permits separation of these monomers and their quantitative determination in acrylate dispersions.
Microbore HPLC column performance and temperature programming capabilities
Authors: McNair Harold , Bowermaster Jeff
Published: May 2005

Microbore columns (1 mm i.d.) are compared to conventional 4.6 mm i.d. columns with respect to speed, efficiency and sensitivity. If column lengths, particule diameter, packing efficiency, mobile phase, and linear velocity are the same, most chromatographic properties such as speed (analysis time), efficiency, pressure drop, and sensitivity are the same. The major differences are the column volumes, the void volumes, and the volumetric flow rates for equal linear flow velocities. The low flow rates of microbore columns (30 to 200 μl/min), conserve solvent and make for easier interfacing to other instruments such as MS, NMR, or FTIR. Temperature programming of microbore HPLC columns produces faster analyses for large k′ values, increased sensitivity (due primarily to sharper peak shape), and increases the range of compounds which can be handled in an isocratic mode.
Selective removal of water in purge and cold‐trap capmary gas chromatographic analysis of volatile organic traces in aqueous samples
Authors: Noij Th. , van Es A. , Cramers C. , Rijks J. , Dooper R.
Published: May 2005

The design and features of an on‐line purge and cold‐trap pre‐concentration device for rapid analysis of volatile organic compounds in aqueous samples are discussed. Excessive water is removed from the purge gas by a condenser or a water permeable membrane in order to avoid blocking of the capillary cold‐trap. Synthetic mixtures covering concentrations ranging from tenths to tens of ppb's and different chemical classes are used to study the effect of various process factors on the efficiency and selectivity of water removal as well as on the purging recovery. The importance of the concentration of the solutes, the flow rate in conjunction with the volume of the purge gas, and the temperature of the condenser, the cold‐trap and the sample is emphasized. Theoretical models describing the purge process and the blocking of the cold‐trap agree fairly well with the highly reproducible experimental results (σ = 2–4%). Both the condenser and the Nafion membrane successfully remove water, although some compounds, dependent on volatility and polarity, are partly or completely lost. It is shown that non‐polar volatile organic compounds are efficiently enriched so that recoveries between 80–100% and a detection limit of 1 ppt can be obtained. The applicability of the system is illustrated on some examples.
Trace analysis of complex organic mixtures using capillary gas‐liquid chromatography and the dynamic solvent effect
Authors: Apps P. J. , Pretorius V. , Lawson K. H. , Rohwer E. R. , Centner M. R. , Viljoen H. W. , Hulse G.
Published: May 2005

A sampling system for high resolution gas‐liquid chromatography, based on the dynamic solvent effect, is described. Volatiles are accumulated off‐line in a concentrator/injector and delivered to the column using an on‐line inlet. Volatiles may be accumulated from gaseous or liquid matrices; they may be transferred to these by gas sparging or solvent extraction of any type of sample. The sampling technique is quantitatively precise; e.g. coefficients of variation of peak percentage areas better than 5% for a range of solutes at a concentration of 2:107. Examples of the application of the sampling system are presented.
Isocratic networks in supercritical fluid chromatography II: Selectivities and effective plate numbers
Authors: Leyendecker Dietger , Leyendecker Dagmar , Schmitz F. P. , Klesper E.
Published: May 2005

The dependence of the selectivity α and the effective plate number, N, on temperature and pressure is shown in three‐dimensional diagrams. The specific system studied was pentane as the mobile phase, unmodified silica as the stationary phase, and a set of four polycyclic hydrocarbons as the test mixture. Temperature and pressure ranges were from 25 to 300°C and from 30 to 75 bar, respectively. The plots for α and N are found to resemble those for capacity ratio, k′, and resolution, R, studied earlier with the same system [1]. A distinct maximum is observed for N in the supercritical region, as found earlier for k′ and R. This applies also to α for the homologous substrate pair naphthalene/anthracene, while the resemblance for α is less pronounced for the pair anthracene/pyrene.
Synthesis and performance of HPTLC plates modified with cyanopropyl‐ and octadecyl‐trichlorosilane
Authors: Colmsjö A. , Ericsson M.
Published: May 2005

Chemical modification of commercial high performance thin‐layer chromatography plates with various mixtures of cyano‐propyltrichlorosilane and octadecyltrichlorosilane is described. Surface coverage by different treatments is demonstrated as well as the variations in chromatographic performance. With regard to the development in aqueous media the utility of CN/ ODS plates compared to ODS plates is also shown.
Long‐acting androgens: Analytical and preparative HPLC of testosterone esters
Authors: Matlin S. A. , Chan L. , Prazeres M. A. , Mehani S. , Cass Q. B.
Published: May 2005

Procedures are described for the normal phase and reverse phase HPLC analysis of testosterone esters having diverse side chains: examples are given of the gram‐scale purification of these compounds using two commercial preparative liquid chromatography and an economical and efficient laboratory‐assembled preparative liquid chromatograph.
Native ethylene glycol in wine: Application of a dead volume free, very fast “deans heart‐cut” system on‐line with multi‐chromatography
Authors: Kaiser R. E. , Rieder R. I.
Published: May 2005

Data about the existence of native HOCH2CH2OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C4) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on‐line with Multi‐Chromatography. It was easy to produce false data by many otherwise useful single column or two‐dimensional separation processes, etc.
Supercritical ammonia as mobile phase in capillary chromatography
Authors: Kuei J. C. , Markides K. E. , Lee M. L.
Published: May 2005

Instrumentation was assembled that allows the use of supercritical ammonia as mobile phase in capillary supercritical fluid chromatography. Several modifications of the typical chromatographic system were necessary, especially with respect to injection and detection. In addition, the stabilities of various polysiloxane stationary phases were studied. The chromatography of polarizable and polar basic materials was demonstrated using a nonpolar polysiloxane stationary phase.
Minimum analysis time in capillary gas chromatography vacuum‐ versus atmospheric‐outlet column operation
Authors: Leclercq P. A. , Cramers C. A.
Published: May 2005

Previous studies on open tubular column operation at vacuum outlet vs. atmospheric outlet pressures focused on comparisons of given columns, or comparisons of columns with the same inner diameters. It was demonstrated that, for a given separation problem, vacuum outlet operation of columns with a constant i. d. always yields the shortest analysis times (under minimum plate height conditions).

In this paper, the comparison of vacuum vs. atmospheric outlet operation is broadened to columns with different dimensions. A general equation for the gain in speed of analysis by vacuum outlet operation of any column, as compared to atmospheric outlet operation of all possible open tubular columns with the same maximum plate number is presented. The resulting equation is further evaluated for thin film columns of different dimensions.

It appears that vacuum outlet operation is beneficial only, in terms of speed of analysis, if low maximum plate numbers are required. The gain in speed of analysis is more pronounced for wide‐bore than for narrow‐bore columns.
Enantiomer and diastereomer resolution of dipeptides by gas chromatography on chirasil‐val
Authors: Koppenhoefer B. , Allmendinger H. , Bayer E.
Published: May 2005

Several dipeptides have been separated into stereoisomers (enantiomers, diastereoisomers, sequential isomers) by GC on the chiral stationary phase Chirasil‐Val. Sufficiently volatile N‐TFA‐dipeptide methyl esters have been formed by derivatization at ambient temperature, thus avoiding racemization (or epimerization, respectively), and peptide cleavage. This novel approach has proven particularly useful for the determination of stereoisomeric composition of dipeptides in biological fluids.
On‐line multidimensional supercritical fluid chromatography/capillary gas chromatography
Authors: Levy J. M. , Guzowski J. P. , Huhak W. E.
Published: May 2005

A new analytical technique combining on‐line supercritical fluid chromatography with capillary gas chromatography has been developed. The supercritical fluid sample effluent is decompressed through a restrictor directly into a conventional capillary gas chromatographic injection port. This technique allows for not only direct (100%) sample transfer from the supercritical fluid chromatograph to the gas chromatograph but also for selective or multi‐step heartcutting of various sample peaks as they elute from the supercritical fluid chromatograph. Heartcut times are determined by monitoring the responses from the flame ionization or ultraviolet absorbance detectors on the supercritical fluid chromatograph. This report describes the operational setup and provides the results of heartcut reproducibility experiments using normal hydrocarbon and aromatic test mixtures. Results from studies where operational parameters were varied, such as GC injector temperature, will also be provided. The potential usefulness of this new technique for selective heartcutting will also be demonstrated using complex hydrocarbon streams.
Implications of the solvent effect in quantitative capillary gas chromatography of minor constituents in mixtures—a study using deuterium labeled and unlabeled benzofluoranthenes
Authors: Cretney W. J. , McLaughlin F. A. , Fowler B. R.
Published: May 2005

Perdeuterated benzofluoranthenes have slightly shorter retention times than their equivalent unlabeled forms in a DB‐5 capillary column. Under column overload conditions, perdeuterated benzofluoranthenes in moderate multifold excesses, which might be encountered in their use as internal standards and carriers for quantitative analysis, are seen to exhibit both normal and reverse solvent effects on their close eluting congeners. In some cases the effects may be used to advantage by knowledgeable analysts, but for the ignorant and unwary the effects can lead to serious errors in identification and quantification.
Analysis of headspace samples using off‐line sorbent trapping coupled with automated thermal desorption and splitless injection onto a cryogenically cooled wide bore capillary column
Authors: Haynes L. V. , Steimle A. R.
Published: May 2005

Gas chromatographic equipment and procedures are described for automated splitless injection of pseudo‐static headspace samples collected externally onto a sorbent trap. The GC microprocessor controls, in sequence, carrier gas backflushing of the sorbent trap for water removal, splitless thermal desorption into a cryogenically cooled wide bore (0.53 mm i. d.) capillary column and oven temperature programming. The method has been routinely applied for profiling the mid‐to‐high boiling compounds (bp 80–225°C) in the headspace of a variety of foods and beverages. Method criteria, advantages and limitations are discussed. FID and NPD chromatograms for brewed coffee and peanut butter volatiles are presented as typical examples.
Gas chromatographic separation of PF3 substituted group 6 metal carbonyl complexes using serially‐coupled capillary columns
Authors: Hwang Wen‐Huan , Clark R. J. , Cooper W. T.
Published: May 2005

The retention of group 6 metal trifluorophosphine carbonyl compounds in serially‐coupled gas capillary columns has been studied as a function of different column configurations. For the trifluorophosphine‐substituted Mo, W, and Cr carbonyls, as well as the analogous Fe compounds, it was observed that the maximum resolution achievable by the coupled column technique was dependent on the order in which the nonpolar (DB‐1) and moderately polar (DB‐1701) columns were connected. The optimum configuration was different, however, for each series M(PF3)x(CO)6−x(M = Cr, Mo, or W) or Fe(PF3)x(CO)5−x. It was also observed that the use of coupled columns of dissimilar polarity can, in some cases, actually decrease resolution relative to that obtained by coupled identical columns (i. e. DB‐1 + DB‐1, or DB‐1701 + DB‐1701).
Isomer‐specific separation of 2,3,7,8‐class congeners of polychlorodibenzodioxins and ‐dibenzofurans on a smectic liquid‐crystalline stationary phase in capillary gas chromatography
Authors: Swerev M. , Ballschmiter K.
Published: May 2005

A smectic liquid‐crystalline stationary phase was used in high resolution gas chromatography for the analysis of the patterns of the chloro‐homologues of the polychlorodibenzodioxins and polychlorodibenzofurans. Unique selectivity for most of the 2,3,7,8‐class congeners was observed. Use of this phase as an alternative to cyanopropylsilicone phases in the isomer‐specific analysis of halogenated and mixed halogenated dibenzodioxins and dibenzofurans is discussed.
Sampling of volatile components using a PTV in the solvent split mode
Authors: Herraiz M. , Reglero G. , Loyola E. , Herraiz T.
Published: May 2005

Several packing materials were evaluated for their sampling performance with a cold programmed temperature vaporizing injector operated in the solvent split (solvent elimination) mode. Evaluations were made by comparing accuracy and precision of the data for mixtures of n‐alkanes, ethyl esters, n‐alcohols, and carboxylic acids covering polarity and volatility ranges typical of compounds present in food samples. Tenax exhibits the most desirable retention characteristics. Careful selection of the experimental conditions lowers losses of volatile compounds by co‐evaporation with the solvent and allows a reliably quantitative analysis. Coefficients of variation of relative (normalized) peak areas and absolute peak area ratios of each compound to the standard are generally less than 2%.
Identification of mononitropyrenes and mononitrofluoranthenes in air particulate matter via fused silica gas, chromatography combined with negative ion atmospheric pressure ionization mass spectrometry
Authors: Korfmacher W. A. , Rushing L. G. , Arey J. , Zielinska B. , Pitts J. N.
Published: May 2005

This paper describes the use of high resolution capillary gas chromatography combined with negative ion atmospheric pressure ionization mass spectrometry (NIAPIMS) for the analysis of an air particulate extract for mononitropyrenes and mononitrofluoranthenes, some of which are powerful bacterial mutagens. The results are compared to those obtained by the electron impact mass spectrometric analysis of the same sample In addition, the NIAPIMS method confirmed the identification of 4‐nitropyrene in the ambient air sample.
High performance liquid chromatographic determination of metoclopramide in plasma and urine and its application to biopharmaceutical investigations
Authors: Nieder M. , Jaeger H.
Published: May 2005

An optimized HPLC method for the quantification of metoclopramide (MCP) in human plasma and urine is described. MCP and internal standard are extracted from alkalinized substrate into diethyl ether and back‐extracted into dilute acid. The analytes are separated with a ternary mobile phase at cyanopropyl‐silica and detected at 312 nm (UV detection). The lower limit of quantification is 0.5 ng/ml in plasma and 50 ng/ml in urine. Optimization of extraction, chromatography, and detection is discussed. The method is selective to numerous common drug substances with excellent accuracy and precision data. After validation, the method is applied to the samples of a pharmacokinetic study. Pharmacokinetic parameters indicate the need for a sophisticated method as tool for optimization of metoclopramide formulations.
Interactions of aldehydes and ketones with the surface of fused silica capillary columns
Authors: Anthony L. J. , Holland R. A. , Heffner S. A.
Published: May 2005

By using gas chromatographic intermediate surface testing to study the surface properties of fused silica capillary tubing, the reversible adsorption of aldehydes and ketones on the fused silica surface has been observed for the first time. It is shown that this interaction can arise from the preferential interaction of carbonyl functional groups at bonded silanol sites on the surface. It is further shown that simple test mixtures containing aldehydes or ketones can be used to probe the concentration of water and bonded silanols on the surface and thus to evaluate capillary manufacturing processes and thermal and chemical surface treatments.
Dynamic headspace enrichment/reinjection for open tubular GC/FTIR analysis of volatiles in polymers
Authors: Schmidt S. , Blomberg L. , Wännman T.
Published: May 2005

An analytical system for the analysis of volatiles entrained in polymers is described. This system is based on a thermal desorption oven connected to a cold trap. After enrichment of headspace vapor, trapped material is reinjected and analyzed by open tubular gas chromatography/Fourier transform infrared spectroscopy, OTGC/FTIR. The thermal desorption oven is designed to provide different modes of sample introduction: use of a pyroprobe; insertion of a piece of quartz tubing with applied sample; or syringe injection. Headspace enrichment is carried out in a piece of fused silica capillary tubing filled with glass beads. The trap may be cooled either electrically using Peltier elements or with liquid nitrogen. A six‐port rotary valve is used for flow switching between enrichment and reinjection modes. All system parameters, temperatures, and timed events, are controlled from the gas chromatograph. Dynamic headspace analysis is demonstrated as a method for polymer characterization.
Comparison of thick film capillaries with packed columns from the point of view of loadability in combination with high resolving power
Authors: Ghijsen R. T. , Poppe H.
Published: May 2005

The present paper compares the potential of high pressure packed column gas chromatography, with a particle size in the range of 30–80 μm and conventional packed column GC. with that of thick film capillaries for obtaining the maximum loadability at a given performance in efficiency and speed of separation. An alternative treatment, discussing the maximum efficiency of the three column types at normalized loadability and speed of separation is given. Known and established relationships describing plate height, loadability, and linear velocity are used to arrive at the said comparisons. The conclusion of the paper indicates a reconsideration of packed column GC for particular types of analyses where large amounts or high concentrations are required in the detection step.
Supercritical‐fluid chromatography: Open columns vs packed columns
Authors: Schoenmakers P. J.
Published: May 2005

Supercritical‐fluid chromatography (SFC) may be performed either in open (capillary) columns or in packed columns. Both approaches have been demonstrated numerous times in the literature. In this contribution it will be attempted to discuss some aspects of columns for SFC. Some advantages of both types of columns will be identified. Attention is paid to the stationary phase film thickness, the speed of analysis, and to the maximum number of theoretical plates (effect of column pressure drop). In this brief contribution many questions will be left unanswered and many significant aspects will be left undiscussed, illustrating that much research remains to be done in this area.
Micropreparative system for enrichment of capillary GC effluents
Authors: Nitz S. , Drawert F. , Albrecht M. , Gellert U.
Published: May 2005

An automated system for preparative gas chromatography with capillary columns is described. The effluet from the capillary column is switched to the FID detector or to the traps by means of a Live‐T switching device. The pneumatics is controlled by a microprocessor so that repetitive sampling can be performed over a period of days in order to enrich sufficient amount of material for NMR or other spectroscopic methods. The effluent containing the compounds is collected in glass tubes filled with column packing material (e.g. Chromosorb coated with 3% OV ‐ 101, crosslinked). The trap temperatue can be adjusted from + 20°C to − 80°C, depending on the trapping material and volatility of trapped substances. The analysis of enriched substances or chromatographic fractions can be performed by thermal desorption of the same traps or by solven elution. The recovery of enriched substances is higher than 90%. High capacity and resolution for enrichment of trace components are obtained with the aid of a double column‐double oven system. Examples of such applications are given.
Evaluation of factors affecting pyrolysis in A microfurnace system
Authors: Dawes P. A. , Cumbers M. K. , Hilling P. A.
Published: May 2005

A styrene isoprene block copolymer, known as Kraton 1107, is used to study some of the parameters involved in the pyrolysis process. Using a continuous mode microfurnace pyrolysis system interfaced to a capillary gas chromatography system, the effect of pyrolysis temperature and gas flows through the pyrolysis chamber were studied. Comparisons in sample introduction methods were made. Introducing the sample in solution, rather than conventional solid sample introduction, was found to offer some advantages.
A technique for coating capillary columns with a very thick film of cross‐linked stationary phase
Authors: Blomberg S. , Roeraade J.
Published: May 2005

A method for preparation of capillary columns and traps with a very thick film (up to 100 μm) of stationary phase is described. The principle of this method is based on an immediate fixation of a film of prepolymer, formed during dynamic coating. Thus, the development of film irregularities, such as are caused by Rayleigh instability is avoided. Fixation of the film is conveniently accomplished by heat‐accelerated crosslinking as was demonstrated in this work, where a commercially available silicone prepolymer (Sylgard 184, Dow Corning) was employed.

The low phase ratio columns which thus can be prepared are interesting both in chromatography with dense mobile phases and as enrichment devices. Examples of the latter application are shown, where trace organic components from air and water were concentrated.
Splitless injection–development and state of the art. Including a comparison of matrix (“dirt”) effects in conventional and PTV splitless injection
Authors: Grob K. , Läubli Th. , Brechbühler B.
Published: May 2005

Kurt Grob introduced splitless injection in 1969. He elaborated most of the working guidelines including the techniques required for reconcentrating the broad intial bands, i.e. the solvent effects and cold trapping. He also designed a vaporizing injector suited for splitless injection. Nevertheless, splitless injection is still often carried out using inappropriate conditions, and many of today's vaporizing injectors are not suited for splitless injection. No autosampler is available that introduces the sample at the appropriate position. Conventional splitless injection is compared to PTV splitless injection for the range of samples that cannot be handled by the anyway superior oncolumn injection, i.e. sample with high loads of involatile byproducts. There is a clear preference for PTV splitless injection as matrix effects observed in conventional splitless injection were found to be substantially reduced or even eliminated.
Fast‐cycle trace analysis of dioxin in flue gas. Monitoring of the incineration of dioxin‐containing waste from seveso
Authors: Blum W. , Szelagiewicz M.
Published: May 2005

The fast trace analysis method used to monitor 2,3,7,8‐TCDD in stack gas during the incineration of the waste from Seveso is described. The sampling of volatile organic compounds from flue gases, distributed between all three aggregation states, is based on a micromethod developed for the trace analysis of water using a specially dimensioned adsorptive charcoal filter (1.5 mg charcoal). In conjunction with subsequent GC/MS measurements the rapid “fast cycle trace analysis” ensured specific 2,3,7,8‐TCDD detection down to 100 pg per m3 flue gas in cycle times of about 1–2 hours.
GC/MS characterization of urinary metabolites of doxylamine succinate: Identification of the aglycones formed from intestinal microflora metabolism of the polar glucuronide metabolites
Authors: Branscomb C. J. , Holder C. L. , Korfmacher W. A. , Cerniglia C. E. , Rushing L. G.
Published: May 2005

This study describes the use of high performance liquid chromatography (HPLC) and capillary gas chromatography/mass spectrometry (GC/MS) in the characterization of polar glucuronide conjugates of doxylamine and their subsequent aglycones following deconjugation. Rat urinary extracts which contained doxylamine and both nonconjugated and conjugated doxylamine metabolites, were examined by HPLC before and after incubation with rat intestinal microflora. The subsequent deconjugated urinary metabolites and the nonconjugated products remaining in the urinary extracts were then isolated, acetylated, and assayed by GC/MS. Incubation with the intestinal microflora indicated that anaerobic bacteria were capable of effecting hydrolytic cleavage of these polar O‐glucuronide metabolites of doxylamine and its demethylated products to their subsequent aglycones. GC/MS analysis was performed using a fused silica DB‐5 GC column and was utilized for the identification of these deconjugated metabolites.
Detection of β‐blocking drugs in urine by capillary column gas chromatography‐negative ion chemical ionization mass spectrometry
Authors: Cartoni G. P. , Ciardi M. , Giarrusso A. , Rosati F.
Published: May 2005

β‐Blocking drugs present in commercial pharmaceutical products are determined in present urine of volunteers between 4 and 24 hours after the administration of a therapeutical dose. The drugs are extracted, hydrolysed, derivatized with pentafluoropropionic anhydride, and analyzed by capillary gas chromatography and electron capture detection. Metabolite identification and drug confirmation is by capillary gas chromatography–negative ion chemical ionization mass spectrometry (GC‐NICIMS). This method is very specific and a sensitivity below 1 ng/ml is obtained.