bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large diameter open tubular columns in gas chromatographic analysis
Authors: Mehran M. F. 
Published: May 2005

AbstractLarge 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractDuring 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

AbstractSmall 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.
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

AbstractReduction 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

AbstractAn 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

AbstractA 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

AbstractA 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

AbstractA 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractMicrobore 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractChemical 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

AbstractProcedures 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

AbstractData 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

AbstractInstrumentation 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

AbstractPrevious 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

AbstractSeveral 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

AbstractA 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.