bluuebunny/crossref_metadata_2025 huggingface dataset:
Peak broadening in isothermal runs due to large retention gaps in capillary GC?
Authors: Grob K.
Published: May 2005

A simple formula is derived which allows estimation of the band broadening due to longitudinal diffusion in retention gaps for isothermal runs with the column held at the injection temperature. The broadening is strongly dependent on the linear gas velocity in the retention gap. If the internal diameters of the retention gap and the separation column are similar, the retention gap may have a length exceeding 100 m, even if the separation column is only 10 m long. A 0.5 mm I.D. retention gap attached to a 0.3 mm I.D. separation column (of interest for automatic on‐column injection) may be several meters long. Retention gaps of 0.3 mm I.D. may be used for on‐column injections into separation columns with I.D's. down to about 0.1 mm.
Quantitation of urapidil and its metabolites in human serum by high performance liquid chromatography
Authors: Nieder M. , Dilger C. , Haerlin R.
Published: May 2005

The antihypertensive agent urapidil (Ebrantil Byk‐Gulden, Konstanz) can be reliably quantitated with three metabolites in human serum using high performance liquid chromatography. Serum is alkalinized and extracted with ethyl acetate. The organic phase is back‐extracted with diluted acid. An aliquot is sampled automatically and chromatographed in an optimized combination of mobile and stationary phase. UV‐detection at 273 nm allows a quantitation limit of 5 ng/ml for all analytes. Precise handling of exact volumes facilitates external calibration. The coefficient of variation for spiked samples is less than 5% within and less than 7% between studies. Application of the method to experimental and clinical pharmacokinetic studies of urapidil is illustrated.
Evaluation of conditions for the HPLC determination of plasma amino acids using precolumn derivatization
Authors: Halfpenny A. P. , Brown Ph. R.
Published: May 2005

For the determination of free amino acids in plasma, the conditions for precolumn derivatization of the amino acids and the chromatographic separation were examined. The isoindole products, formed by the reaction of the primary amino acids with orthophthalaldehyde (OPA), were readily separated by RPLC and detected spectrofluorometrically using an excitation wave‐length of 300 nm and an emission cut‐off filter of 440 nm. Since the sensitivity of this method permits determination of amino acids in the femtomole range, the analysis can be performed on samples as small as 10 μl of filtered plasma or serum. The separation is achieved in approximately 35 minutes with good precision for the majority of the amino acids.
Comparative chemical analysis of commercial creosotes and solvent refined coal‐II materials by high resolution gas chromatography
Authors: Wright C. W. , Later D. W. , Wilson B. W.
Published: May 2005

The chemical composition of a commercially available creosote was compared to a direct coal liquefaction product, i.e., solvent refined coal‐II fuel oil blend (SRC‐II FOB) using high resolution gas chromatography (HRGC). In addition, hydrogenated products of these materials were studied. Samples were fractionated by chemical class on neutral alumina. Those fractions previously shown to be the most mutagenic and tumorigenic in laboratory bioassays of coal‐derived materials were analyzed and compared by HRGC and gas chromatography/mass spectrometry (GC/MS). Individual components were tentatively identified and quantitated. Although similar chemical components were present in the creosote and SRC‐II FOB fractions studied, the creosotes had higher concentrations of heavy molecular weight materials and a lower ratio of alkylated to parent polycyclic aromatic compounds than the coal liquefaction products. The creosote samples also had a significantly higher concentration of components which eluted in the polycyclic aromatic hydrocarbon (PAH) chemical class fraction. Amino‐substituted PAH were present in both nonhydrogenated coal liquid and creosote materials. The creosote and SRC‐II FOB crudes and nitrogen‐containing polycyclic aromatic compound (NPAC) chemical class fractions expressed similar microbial mutagenicity. Based on chemical analysis data, the predicted tumorigenic potency of the creosote in laboratory bioassay systems would be equivalent to or greater than the SRC‐II FOB.
Hydrothermal treatment of fused silica capillary columns
Authors: Ogden M. W. , McNair H. M.
Published: May 2005

The activity of fused silica capillary tubing has been shown to vary considerably, which severely influences the reproducibility of column deactivation and inertness. Methods for producing a reproducible, high activity surface with maximum hydroxylation by various hydrothermal treatments were evaluated. Columns pretreated with 20% nitric acid at 200°C for 10 hours, deactivated with D4, coated with OV‐73, and crosslinked with azo‐tert‐butane were found to possess excellent inertness for sensitive analytes such as alcohols, amines, and alkaloid drugs.
Sensitive determination of perfluorocarbon tracers in air by intermediate trapping and GC‐ECD analysis
Authors: de Bortoli M. , Pecchio E.
Published: May 2005

This paper reports on the development of a simple method for the determination of two perfluorinated hydrocarbons (C7F14 and C8F16) in air down to 0.2 ng/m3, for long range atmospheric tracer experiments. The organic vapors are adsorbed on graphitized carbon black, desorbed thermally and determined by capillary GC‐ECD at subambient temperature. Optimization of the experimental conditions is described. The tracers were tested in a field experiment where SF6 was also released and the agreement was satisfactory.
Modification of a packed GC injector to a versatile capillary injector
Authors: Etzweiler F.
Published: May 2005

A modification of a packed GC injector to a capillary injector is presented using a simple device which is connected to the GC column by an adsorption‐free connector. It permits injections of large sample volumes up to 500 μl hexane solutions on normal 0.3 mm i.d. capillary columns. No special requirements for the stationary phase are necessary. Involatile residues remain inside the device which can be exchanged easily. High performance of separation and quantification is achieved.
The use of glass and fused silica open tubular columns for the separation of structural, configurational, and optical isomers by selective complexation GC: Sec‐alcohols and ketones
Authors: Schurig V. , Leyrer U. , Weber R.
Published: May 2005

The use of glass and fused silica open tubular columns for selective separation of structural, configurational, and optical isomers (enantiomers) of underivatized aliphatic alcohols and ketones by complexation gas chromatography on optically active metal chelates is described. The method represents a powerful analytical tool for the precise determination of diastereomeric (d.e.) and enantiomeric (e.e.) excesses in asymmetric syntheses and in natural product characterization. The direct screening of the enantiomeric composition and absolute configuration of terpinene‐4‐ol, the aggregation phermone of Polygraphus poligraphus (L), is described.
The effects of modifiers in supercritical fluid chromatography
Authors: Levy J. M. , Ritchey W. M.
Published: May 2005

Investigations have been initiated to examine the basic elements of resolution and how they vary individually and collectively in terms of modifiers used in supercritical fluid chromatography (SFC). Capacity factors (k′) have been determined for a mixture of polynuclear aromatic hydrocarbons from SFC experiments as function of modifier identity and concentration using different stationary phases. Using carbon dioxide as the primary mobile phase, the modifiers investigated included methanol, 2‐methoxy ethanol, 1‐propanol, tetrahydrofuran, dimethyl sulfoxide, acetonitrile, sulfur hexafluoride, and freon 11.
Characterization of Saccharomyces Sp. through determination of amino acid profiles by capillary gas chromatography
Authors: Vasconcelos A. M. P. , Neves H. J. Chaves Das
Published: May 2005

The Saccharomyces strains uvarum, montuliensis, bayanus, capensis and florentinus were grown in liquid media prepared from a 1% aqueous glucose solution to which 0.05% of ammonium sulfate or urea were added as the only nitrogen supply. The amino acids exuded during incubation were isolated by cation exchange and derivatized as the corresponding N,O‐heptafluorobutyryl isopropyl esters. Separation was achieved on a highly deactivated glass capillary column coated with OV‐101. A characteristic amino acid profile was obtained for each of the species studied, allowing the construction of a chemotaxonomic tree, on the basis of present or absent acids.
Automatic system for rapid analysis of volatile compounds by purge‐and‐cold‐trapping/capillary gas chromatography
Authors: Badings H. T. , de Jong C. , Dooper R. P. M.
Published: May 2005

A system for automatic analysis of volatile compounds by purge‐and‐cold‐trapping/capillary gas chromatography is described. It is suitable for analysis of volatile compounds in a wide variety of samples, such as water, food products and environmental samples. Possibilities and limitations of the system are evaluated in relation to several parameters. The efficiency of different types of cryogenic trap (open tubular, coated, packed) is also investigated; it depends on purge‐flow rate, temperature of trapping, and total purge volume. Examples of the analysis of volatile compounds in foods and water are given.
Optimum performance of capillary GC columns as a function of tube diameter and film thickness under various operating conditions. Computer program for calculation of H‐ū curves and minimum analysis times
Authors: Leclercq P. A. , Cramers C. A.
Published: May 2005

The Golay‐Giddings and Poiseuille equations are used to derive equations for the calculation of the maximum plate number and minimum time conditions for given columns at fixed, but selectable, outlet pressures. In addition, expressions are presented for the determination of minimum analysis times for separation problems requiring given plate numbers. In this instance, the optimum column length can be calculated as a function of outlet pressure. A Basic computer program, incorporating the equations for the various optima, together with the H‐ū curves, is described. Input variables are either column length or desired plate number, column diameter, film thickness, capacity ratio of the solute, column outlet pressure, seperation temperature, and carrier gas. The carrier gas viscosity is automatically calculated in the case of hydrogen, helium, or nitrogen. For these gases, and if the solute is a n‐alkane, the diffusivity of the solute in the mobile phase is calculated. In this case, the carbon number of the solute is needed in the computation.

For high molecular weight polydimethylsilicone phases (e.g. SE‐30), the program can approximate the diffusivity of n‐alkanes in the stationary phase at the given temperature as a function of the carbon number. Of course, manually entered values of viscosity and diffusion coefficients can be included in the calculations.
Synthesis of siloxane stationary phases for capillary gas chromatography and supercritical fluid chromatography
Authors: Ogden M. W. , McNair H. M.
Published: May 2005

A comparison is made between dichlorosilanes and cyclic siloxanes as starting materials in the synthesis of stationary phases for capillary gas chromatography (CGC) and supercritical fluid chromatography (SFC). Siloxanes containing one or more of the side groups methyl, vinyl, phenyl, and cyanoethyl in various ratios were synthesized and compared. These phases were characterized by chromatographic (gel permeation, GPC), spectroscopic (IR, 1H NMR, 29Si NMR), and thermal (DSC) methods. Coated fused silica columns were evaluated with respect to polarity, crosslinkability with several free‐radical initiators, and thermal stability. A new liquid phase, 7% cyanoethyl, 7% phenyl, 1% vinyl methyl polysiloxane is shown to be more polar than OV‐1701, more temperature stable, easily crosslinked and suitable for use in supercritical fluid chromatography.
Programmed‐temperture split‐splitless injection of triglycerides: Comparison to cold on‐column injection
Authors: Hinshaw J. V. , Seferovic W.
Published: May 2005

The performance of split and splitless programmed‐temperature (PTV) injection is compared to cold on‐column and hot (classical) split injection for the analysis of triglycerides on an apolar capillary gas chromatographic column. Quantitative accuracy and precision of PTV injection are determined for a synthetic mixture of triglycerides relative to cold on‐column injection.
Rapid analysis using capillary supercritical fluid chromatography
Authors: Wright B. W. , Smith R. D.
Published: May 2005

Capillary supercritical fluid chromatography (SFC) is proving to be a viable and useful separation method for thermally labile and nonvolatile materials. As with other capillary chromatographic techniques, very fast separations can be accomplished by sacrificing total efficiency and optimizing the conditions for rapid analysis. This is achieved using short, small‐bore capillary columns, increased mobile phase linear velocities and very fast pressure programming rates. These principles are demonstrated for the rapid separation of selected component systems.
Supercritical fluid chromatography/Fourier transform infrared microspectrometry
Authors: Pentoney S. L. , Shafer K. H. , Griffiths P. R. , Fuoco R.
Published: May 2005

The feasibility of supercritical fluid chromatography/Fourier transform‐infrared (SFC/FT‐IR) microspectrometry is presented. In this approach to SFC/FT‐IR, the chromatographic eluates are aspirated from the restrictor directly onto the surface of a moving window which then passes into the beam focus of an infrared microscope. Because the mobile phase is gaseous at ambient conditions, elimination of the mobile phase is easily accomplished. Detection limits in all interfaces between a chromatograph and an FT‐IR spectrometer in which the mobile phase is eliminated are determined in large part by the area over which the sample is deposited. We have shown that SFC eluates can be condensed at ambient temperature into spots of 100 to 200μm in diameter. The microscope interface therefore serves to increase the sensitivity of the SFC/FT‐IR measurements of these spots and detection limits in the low nanogram range are possible. Preliminary results obtained before any real attempts were made to optimize the deposition process indicate that identifiable spectra can be obtained in real time at the 50 ng level for chromatographic separations performed with a 100μm i.d. wall coated open tubular column. Reproducible reconstructed chromatograms are obtained as each deposited eluate travels through the beam focus of the microscope. The concentration profile of deposited peaks was determined by IR measurements performed at 50 μm increments over the width of the peak to ascertain the deposition size. The results described in this paper, while not yet optimized, indicate the great potential of SFC/FT‐IR microspectrometry.
Mathematical dead time determination and calculation of the constants of the n‐alkane retention time curve on OV polymethyl phenylsilicone stationary phases in gas chromatography
Authors: Touabet A. , Badjah Hadj Ahmed A. Y. , Maeck M. , Meklati B. Y.
Published: May 2005

The column dead time and the constants of the n‐alkane retention time curve in gas‐liquid chromatography are calculated by the Wentworth iterative method on series of OV polymethylphenylsilicones with an increasing percentage of phenyl substituent. The values obtained are in good agreement with those calculated by the methods of Gröbler and Kaiser and with the experimental ones reported in the literature for stationary phases studied at 120°C and 150°C. The scatter of experimental retention times of n‐alkanes and tM and b and c and Kováts retention indices are calculated.
Improvement of a cryogenic preconcentration unit for C2 ‐ C6 hydrocarbons in ambient air at ppt levels
Authors: Schmidbauer N. , Oehme M.
Published: May 2005

A previously described method for the quantitative analysis of C2 ‐ C6 hydrocarbons in the ppt range based on cryogenic preconcentration has been improved further. Problems caused by condensation of O2 and traces of water from the sample were overcome using a modified dyring procedure and a tandem preconcentration trap. In addition, the flow path through the unit was simplified further. Technical details are given. The reproducibility of both quantitative results and retention times was improved by these modifications. Typical standard deviations were in the order of 2% at the 200 ppt level.
Current technological challenges in capillary supercritical fluid chromatography
Authors: Lee M. L. , Markides K. E.
Published: May 2005

In cases where high efficiency is required to resolve complex mixtures of either thermally labile or nonvolatile organic compounds, capillary supercritical fluid chromatography may be the most desirable analytical method. While great strides in this new technology have been made over the last few years, several problem areas are requiring increased attention. These include sample introduction systems, pressure reduction at the end of the column, column stability in various supercritical mobile phases, and migration of polar solute molecules. This paper describes the state‐of‐the‐art in capillary SFC with emphasis on the progress made and future needs in the solutions to these specific problems.
Factors controlling electroosmotic flow in open‐tubular capillaries in electrokinetic chromatography
Authors: Terabe S. , Utsumi H. , Otsuka K. , Ando T. , Inomata T. , Kuze S. , Hanaoka Y.
Published: May 2005

Effects of pH, concentration of sodium dodecyl sulfate (SDS), additives, and coatings of polymers on the inner wall of fused silica tubing on electrokinetic migration were investigated with SDS solutions. The increase in SDS concentrations caused a substantial increase of the electrophoretic velocity of the SDS micelle but little affected the electroosmotic velocity veo under a constant applied voltage. No significant change in veo was observed either when the pH of the solution was varied from 5.5 to 9 or when additives such as hydroxypropyl cellulose were employed. Compared with an uncoated tube, electroosmosis became stronger in a fused silica tube coated with methyl silicone but weaker in one coated with polyethylene glycol 20M.
Considerations of speed and efficiency in capillary gas chromatography
Authors: Cramers C. A.
Published: May 2005

The analysis time for a given resolution is a complex function of stationary phase selectivity, column radius, and thickness of the stationary phase film. Variation of these parameters has a large effect not only on analysis time, but also on the column inlet pressure and other instrumental requirements. The minimum amount that can be reliably detected as well as the maximum sample capacity of a column are strongly related to the selected column dimensions.
Separation of isotopic compounds by reversed‐phase liquid chromatography. Effect of pressure gradient on isotope separation by ionization control
Authors: Tanaka N. , Yamaguchi A. , Hashizume K. , Araki M. , Wada A. , Kimata K.
Published: May 2005

Isotope separation utilizing ionization control in reversed‐phase liquid chromatography was studied. Several organic acids and bases labeled with oxygen‐18 and nitrogen‐15 were successfully separated from unlabeled compounds by using either 6‐m microbore columns or recycle chromatography with short columns of conventional size. Differences in the separation factors for the same isotopic mixtures were observed between the two chromatographic systems, and attributed to the difference in the pressure gradient along the columns in the two systems. The steep pressure gradient existing in the short recycle columns resulted in an increase in the peak width and the separation factor for oxygen isotopic compounds, and a decrease in the peak width and the separation factor for nitrogen isotopic compounds.
Optimization and identification in any kind of multi‐step temperature programmed gas chromatography
Authors: Peichang Lu , Bingcheng Lin , Xinhua Chu , Chunrong Luo , Guangda Lai , Haochun Li
Published: May 2005

The theory which predicts the retention time, retention temperature, and peak width for any kind of multi‐step TPGC and the principle of optimization has been described. Software for optimization and identification in TPGC has been developed on the basis of this theory. It has also been proven that the relationship between peak width in TPGC and the derived or “invented” retention time is similar to that between peak width and retention time in isothermal processes. The validity of the software has been proved by using it to predict retention temperature, retention time, and peak width for any kind of temperature programming and to predict the optimum temperature program for separation of a multihomolog mixture of industrial alcohols and 15 enantiomeric pairs of amino acids.
Analysis of triglycerides by capillary gas chromatography with programmed‐temperature injection
Authors: Hinshaw J. V. , Seferovic W.
Published: May 2005

The capillary gas chromatographic analysis of complex naturally occurring and food‐product triglyceride mixtures is accomplished qualitatively and quantitatively on columns coated with methyl and methyl‐phenyl (65%) silicones using programmed‐temperature split/splitless and on‐column injection. Faster analysis times are achieved using elevated initial column oven temperatures with cold initial injector temperatures.
HPLC of anions on coated reversed phase columns using indirect UV‐detection and eluents containing nitrophthalic acids
Authors: Fröhlich D. H.
Published: May 2005

Analysis of anions by HPLC has been optimized in the direction of reduced analysis times with standard reversed phase columns and UV detection. This was achieved by use of a new eluent containing 3‐nitrophthalic acid and small proportions of acetonitrile. Resin‐based and silica‐based anion exchangers of varying ion‐exchange capacities are prepared with cetyltrimethylammonium bromide by a rapid dynamic coating technique. Some new, strong eluents containing nitrophthalic acids are evaluated and compared with an eluent containing potassium hydrogen phthalate. Addition of acetonitrile was found to improve the retention behavior of mono‐ and divalent anions. An automatic system was developed for the analysis of chloride, nitrate, and sulfate in drinking water. It is shown that a water sample can be analyzed in less than two minutes on a column of 25 mm length.
Capillary gas chromatographic analysis of highly brominated fire retardant compounds
Authors: Anthony L. J. , Kozlowski S. A. , Holland R. A.
Published: May 2005

We report the development of a capillary gas chromatographic method, superior to existing packed column methods, for the analysis of highly brominated additive fire‐retardants, including decabromodiphenyl ether (1) and decabromodiphenoxyethane (II). Neither compound has been analyzed previously by capillary GC, and there are no published methods for (II). For (I), the new method is 5–10 times faster than an analogous packed column method, and it has 100 times lower detection limits and twice the precision of a gas chromatographic/mass spectrometric method. For (II), the capillary method is 30–50% faster than an unpublished liquid chromatographic method. The greater efficiency of the capillary method makes possible the complete resolution (R ≥ 1.25) of structurally very similar compounds (e.g. compound (II) and its Br9Cl1 and Br8Cl2 analogues). With the new method, commercial preparations of (I) and (II) can be rapidly analyzed, and samples from combustion and pyrolysis experiments can be evaluated for compositional changes.
Stabilization of Ucon LB‐550‐X stationary phase film by hydrogen chloride
Authors: Janák K. , Tesařik K. , Horká M.
Published: May 2005

The influence of gaseous hydrogen chloride on the efficiency and thermal stability of a Ucon LB‐550‐X stationary phase film has been studied under various working conditions. The efficiency of capillary columns was found to be unchanged or even increased, and the upper working temperature increased by 40–50°C. Nor did the action of hydrogen chloride change the polarity of the columns studied.
Optimizing gas chromatographic separations
Authors: Freeman R. R. , Jennings W.
Published: May 2005

While separations based on the use of stationary phases specifically designed to maximize solute alphas can, in the strictest sense, be precisely optimized only under specific isothermal conditions, the approach has previously been used even with temperature programmed separations. Selectivity can by further “tuned” by (1) differential variations in the carrier gas velocity through dissimilarly coated coupled columns, and (2) temperature variations in columns of at least moderate polarity. This paper explores the latter approach.
High precision trace analysis in capillary gas‐liquid chromatography using an inlet based on the static solvent effect
Authors: Lawson K. H. , Pretorius V. , Apps P. J.
Published: May 2005

A sample inlet, based on the static solvent effect has been designed and constructed. The inlet can handle samples up to 20 μl which allows for the detection, using an F. I. D., of constituents in the parts per billion range. The reproducibility of the inlet in terms of peak percentage area is around 1% relative standard deviation over a range of chemical types.
High oven temperature — cold on‐column injection for the automated CGC analysis of high molecular weight compounds such as triglycerides
Authors: Termonia M. , Munari F. , Sandra P.
Published: May 2005

Modification of the Carlo‐Erba cold on‐column injector for (automated) analysis of high molecular compounds at high oven temperature is described. The secondary cooling tube of the cold on‐column injector is replaced by a lengthened tube through which a high air flow is directed. The injection site is maintained at 65–70 °C while the oven is at high temperature (≷ 300 °C). For automated injection, a short deactivated precolumn of 22 to 30 cm × 0.53 mm i.d. is coupled to the analytical column via a butt connector with make‐up gas supply. For a triglyceride mixture, automatically injected at 300 °C, the mean % deviation for all peak areas was 1.8% and the mean % deviation for all retention times was 0.09 % for five consecutive runs.
HPLC separation and determination of astacene, semiastacene, astaxanthin, and other keto‐carotenoids
Authors: Vecchi M. , Glinz E. , Meduna V. , Schiedt K.
Published: May 2005

Direct HPLC analysis of astacene, semi‐astacene, and astaxanthin isomers in the presence of other keto‐carotenoids was achieved using silica gel coated with H3PO4. A method was developed for the preparation of such stationary phases with reproducible chromatographic properties.
Determination of amino acids by gas chromatography using a wide bore capillary column
Authors: Moodie I. M. , Burger J. A. , Labadarios D.
Published: May 2005

A procedure is described in which a wide bore capillary column is used as an alternative to the more traditional packed column for the quantitative analysis of amino acids as their N‐heptafluorobutyryl isobutyl ester (HBB) derivatives. The column, installed in a gas chromatograph previously configured for use with a packed column, is shown to give good reproducibility by repeated determination of amino acid response factors (RSD values for all amino acids are below 3%). A number of problems, encountered during the use of this column, are discussed and suitable techniques to overcome them are reported.
Reversed‐phase thin‐layer chromatography of phenolic compounds
Authors: Tesařová E. , Snopek J. , Smolková‐Keulemansová E.
Published: May 2005

On a chemically‐bonded C18 stationary phase, the possibilities were studied of affecting the retention behavior of selected phenolic compounds (dianes, biphenyl and its hydroxy derivatives, naphthalene and its hydroxy derivatives and nitrophenols) by adding tensides to the mobile phase of water with methanol. The data obtained have been Interpreted from the point of view of interactions in the given separation system.
On the stability of micro‐LC columns (packed fused silica capillary columns)
Authors: De Weerdt M. , Dewaele C. , Verzele M.
Published: May 2005

The life expectancy and resistance to flow, pressure shocks, solvent gradients, and bending of packed fused silica capillary columns (Micro‐LC) are discussed.
Contour diagrams for the presentation of separation quality in two‐dimensional thin layer chromatography
Authors: Steinbrunner J. E. , Malik D. J. , Nurok D.
Published: May 2005

Several methods for evaluating separation quality in two‐dimensional thin layer chromatography are discussed. These include using either the distance between spot centers for the pair of solutes that is the most difficult to separate in a mixture, or the value of a suitable, separation function, as criteria of overall separation quality. Contour diagrams may be constructed in which solvent compositions for each of the two‐dimensional developments are the independent variables and spot separation or the value of a suitable function is the dependent variable. Such diagrams indicate which are the best and the worst regions of the two‐dimensional solvent domain. These diagrams should be of value for comparing different solvent systems for two‐dimensional thin layer chromatography.
On the influence of the solute sample size on temperature‐programmed retention indices
Authors: Wang Tiansong , Sun Yiliang
Published: May 2005

The effect of the solute sample size on the measurement of temperature‐programmed retention indices (ITP) has been studied on glass capillary columns with different stationary phases, film thicknesses, and temperature programs. The sample capacity of a solute is little affected by the parameters of temperature program, i. e. initial temperature and heating rate. However, it has been found that in a temperature programmed run, allowable sample sizes for high ITP values are lower than for low ITP values. About 10 ng of each compound is recommended as the sample size for accurate measurement of ITP values on commonly used capillary columns.
Determination of polychlorinated biphenyls in sediment by on‐line narrow‐bore column liquid chromatography/capillary gas chromatography
Authors: Maris F. A. , Noroozian E. , Otten R. R. , van Dijck R. C. J. M. , de Jong G. J. , Brinkman U. A. Th.
Published: May 2005

Narrow‐bore column liquid chromatography coupled on‐line with capillary gas chromatography (LC/GC) is used for the determination of polychlorinated biphenyls (PCBs) in sediment via a heart‐cutting technique. This method is compared with a method in which two off‐line column clean‐up steps are used with subsequent analysis by capillary gas chromatography. For the LC/GC analysis the recovery of PCBs was 90–100%. For two sediment samples from the river Meuse the LC/GC and the other, more laborious method showed good agreement.
Gas chromatography of plasma amino acids using a wide bore column: Comparison with packed and capillary columns
Authors: Labadarios D. , Moodie I. M. , Burger J. A. , Shephard G. S.
Published: May 2005

A procedure is described in which a wide bore glass capillary column is used as an alternative to the more traditional packed column in the analysis of amino acid levels in plasma. The coefficients of variation for all amino acids (with the exception of aspartic acid) were better than 11% with recoveries ranging from 81% to 122%. The data are compared with the corresponding results obtained using a packed column and show significant differences (p < 0.005) between values for glycine, serine, isoleucine, proline, methionine, aspartic acid, phenylalanine, and lysine. A similar comparison between results from the wide bore and the fused‐silica open tubular (FSOT) column shows better agreement. Adjustment of chromatographic conditions for the wide bore analysis yields results in good agreement with those from FSOT analysis but which still differe significantly from the backed column data.
Evaluation of fused‐silica capillary columns for GC/ECD analysis of chlorinated hydrocarbons listed in EPA method 8120
Authors: Lopez‐Avila V. , Dodhiwala N. , Beckert W. F.
Published: May 2005

Four mega‐bore, one wide‐bore, and one narrow‐bore fused‐silica capillary columns were evaluated for their applicability to the GC/ECD analysis of 22 chlorinated hydrocarbons, some of which are currently targeted by EPA Method 8120. No one column can resolve all 22 compounds investigated here. Four compounds (two pairs) are coeluting on the SPB‐35, DB‐210, DB‐WAX, and DB‐519 fused‐silica capillary columns, five compounds (two groups) are coeluting on the DB‐1301 fused‐silica capillary column, and ten compounds (five pairs) are coeluting on the SPB‐5 fused‐silica capillary column. The analysis time varies between 30 and 50 min. The order of elution of the chlorinated benzenes seems to depend on their boiling points rather than on the polarity of the liquid phase. The retention times of an additional nine chlorinated toluenes, eight chlorinated xylenes, and five chlorinated naphthalenes are also reported. Electron capture detector linearity is reported for the DB‐210 fused‐silica capillary column. Five brominated compounds were investigated as possible internal standards for Method 8120.
Capillary gas chromatographic determination of major and minor metabolites of aromatic solvents in human urine
Authors: Korn M. , Wodarz R. , Drysch K. , Schmahl F. W.
Published: May 2005

Aromatic solvents are involved in manifold areas of industry and craft. Inhaled solvent vapors are a known health hazard to workers. For medical prevention and toxicological assay specific laboratory methods for urinary metabolites are necessary. An economical capillary gas chromatographic procedure is described which is suitable for routine analysis of major metabolites, sensitive for the determination of minor metabolites, and effective for the separation of chiral metabolic intermediates.
Selective determination of organofluorine compounds by capillary column gas chromatography with an atmospheric pressure helium microwave‐induced plasma detector
Authors: Brill J. H. , Narayanan B. A. , Doom J. P. , McCormick J. P.
Published: May 2005

Fluorinated analogs of compounds typical of those found in metabolic and other biological studies are detected with high selectivity using a gas chromatograph/microwave‐induced plasma detector (GC‐MIPD), which permits fluorine‐selective detection by monitoring the emission at 685.6 nm. Using the described atmospheric pressure helium‐sustained plasma detector, the minimum detectable level, fluorine selectivity (relative to carbon), and linear dynamic range of this GC‐MIPD system were determined to be 4.8 pg‐F/s, 1060, and 5000, respectively. The utility of this GC‐MIPD system for the selective detection of organofluorine compounds is demonstrated by its application in the analysis of the metabolic fate of a fluorinated substrate administered to a mixture of wheat germ phosphatase and potato apyrase, as well as by analysis of synthetic mixtures.
Determination of column selectivity toward polycyclic aromatic hydrocarbons
Authors: Sander L. C. , Wise S. A.
Published: May 2005

An empirical test is described for the evaluation of column selectivity in reversed‐phase liquid chromatography. Using a test mixture of three polycyclic aromatic hydrocarbons (PAH), overall column selectivity toward PAH was assessed for over 20 different commercial C18 columns. Retention behavior was correlated to phase type (i.e., monomeric and polymeric surface modification chemistry) for custom synthesized phases. A classification scheme is proposed in which commercial C18 columns are grouped into three classes based on retention behavior: monomeric‐like, polymeric‐like, and intermediate phase selectivity toward PAH. Correlation of retention behavior of the test mixture with the separation of PAH mixtures and with more general column properties (e.g., phase thickness) is discussed.
High‐performance ligand‐exchange chromatography of amino acids on chiral stationary phases
Authors: Carunchio V. , Messina A. , Sinibaldi M. , Fanali S.
Published: May 2005

Three chiral stationary phases, obtained by grafting silica gel with (‐)‐trans‐1,2‐cyclohexanediamine, were studied for the resolution of α‐amino acids by ligand‐exchange chromatography. The packings were prepared by bonding the chiral ligand to silica gel via different hydrocarbon spacers. Separation of the optical isomers was accomplished by eluents containing a constant concentration of copper(II) acetate (0.05mM). The elution sequence of amino acids was found to be dependent on the grafting reaction selected to prepare the chiral packings.
High resolution gas chromatography of tobacco smoke: The contributions of kurt grob
Authors: Ogden M. W.
Published: May 2005

The contributions made by Kurt Grob to tobacco science are reviewed with emphasis on the application of high resolution gas chromatography to tobacco smoke analysis. Highlighted are his pioneering achievements in the preparation and use of glass capillary columns, GC‐MS, and splitless injection.
Simultaneous coupling of capillary supercritical fluid chromatography and high temperature glass capillary gas chromatography to a mass spectrometer
Authors: Blum W. , Grolimund K. , Jordi P. E. , Ramstein P.
Published: May 2005

The coupling of glass capillary supercritical fluid chromatography to a high temperature GC/MS system via a micrometeradjustable glass capillary interface including an integrated pressure restrictor is described. With this coupling device, both complementary capillary chromatographic methods retain their full independence and flexibility.

It is shown that in supercritical fluid chromatography glass fulfils all the requirements of a suitable support material. The preparation of narrow bore glass capillary columns (0.06 mm i.d.), coated with chemically bonded and crosslinked fluids with a film thickness of about 0.6 μm, which exploit the merits of OHterminated polysiloxanes as stationary phases is discussed. The application of glass capillary SFC is demonstrated and compared with examples given in the literature.
Computer controlled micropreparative isolation and enrichment from GC capillary columns and subsequent sample handling
Authors: Etzweiler F.
Published: May 2005

This paper describes a computerized system for micropreparative enrichment of components from a mixture being separated on a capillary column. All electronic components are commercially available. Programming was performed in BASIC so that users can easily adapt the program to their own special needs.

The enrichment procedure is based on a repetitive absorption of eluting compounds after separation from a capillary column, by sucking them through an absorption tube mounted at the outlet splitter. In order to perform this procedure reliably, the system searches for reference peaks which can stem from componetns of the mixture or from deliberately added reference compounds. Use of error diagnostics prevents contamination of the collected fractions in case of system failures. Optimization is easily performed during a supervised GC run in a semiautomatic mode. Using the function keys of the computer, the operator can adjust injection volume, measure the base line drift at any retention time, and perform reference peak allocation and peak switching until optimal conditions have been found.

The system presented has been in operation for several years in our laboratory where, in some cases, the mixture had to be injected onto the capillary column over 500 times to obtain the amount of pure component (10–1000 μg) necessary for NMR structure elucidation. However, recording of meaningful spectra of such small amounts requires special precautions in sample handling. This technique can also be applied for sample recovery after analysis by non‐destructive elucidation methods or by chemical microreactions without loss.
Simultaneous accumulation and derivatization of volatiles using the dynamic solvent effect
Authors: Centner M. R. , Apps P. J. , Viljoen H. W. , Pretorius V.
Published: May 2005

A method for the derivatization of volatiles collected using the dynamic solvent effect (DSE) is described. Trimethylsily ethers and esters (using N,O‐bis‐trimethylsilyltrifluoracetamide) are produced on the porous bed of a DSE concentrator either during or after collection of airborne volatiles. Peak areas obtained in the gas chromatographic analysis of test compounds gave coefficients of variation of less than 10% for amounts considerably less than 100 ng. Little, if any, adsorption or other loss of compounds occurs. The analysis of the volatiles collected from an individual queen of the honeybee, Apis mellifera scutellata, is presented to illustrate the utility of the technique.
Cyclodextrins as chiral stationary phases in capillary gas chromatography. Part III: Hexakis(3‐O‐acetyl‐2,6‐di‐O‐pentyl)‐α‐cyclodextrin
Authors: König W. A. , Lutz S. , Colberg C. , Schmidt N. , Wenz G. , von der Bey E. , Mosandl A. , Günther C. , Kustermann A.
Published: May 2005

The properties of hexakis(3‐O‐acetyl‐2,6‐di‐O‐pentyl)‐α‐cyclodextrin as a chiral stationary phase for capillary gas chromatography are described. For the first time the enantiomers of a series of different lactones are separated and their order of elution is assigned. Moreover, the enantiomers of trifluoroacetylated aldols and amino alcohols, the cyclic carbonates of 1,2‐diols, 1,3‐diols, O‐alkylated glycerols, and some chiral pharmaceuticals are also separated on the new chiral phase. The modified α‐cyclodextrin is stable above 200°C.
Electrochemical, fluorescence, and UV detection for HPLC analysis of various cysteine derivatives
Authors: Ziegler S. J. , Sticher O.
Published: May 2005

Electrochemical (ECD), fluorescence (FLD), and UV spectrophotometric (UVD) detection were used to monitor various S‐alk(en)yl‐L‐cysteines and their corresponding sulfoxide isomers following pre‐column derivatization with o‐phthaldialdehyde‐tert‐butylthiol and separation by reversed‐phase HPLC. Recording of hydrodynamic voltammograms, FLD stop‐flow scanning, and on‐line captured UV spectra were methods used for establishing optimal detector settings which were defined as a compromise between favorable selectivity and high sensitivity. Optimal detector settings were found at: (A) 750 mV vs. Ag/AgCl for ECD; (B) excitation at 230 nm and emission at 420 nm for FLD; and (C) 337 nm for UVD. Various aspects of detector practicability such as selectivity, baseline disturbances due to excessive reagent, scanning possibilities, as well as detection limits were evaluated and compared. Minimal detectable amounts of the compounds were in the range of 130‐160 fmol for ECD, and 2.5‐3.5 pmol and 13‐16 pmol for FLD and UVD. In addition, the possibilities and benefits of detector coupling were examined.
Determination of gas phase nicotine and 3‐ethenylpyridine, and particulate phase nicotine in environmental tobacco smoke with a collection bed – capillary gas chromatography system
Authors: Tang H. , Richards G. , Gunther K. , Crawford J. , Lee M. L. , Lewis E. A. , Eatough D. J.
Published: May 2005

A combined sampling and analysis technique for the determination of gas phase nicotine and 3‐ethenylpyridine, and of particulate phase nicotine in environmental tobacco smoke with capillary gas chromatography is reported. The major advantage of the technique is that all of the collected particulate phase material is analyzed by thermal desorption of the collected material rather than by analysis of only a fraction of the sample extracted from the collection medium. A Teflon filter microtube is used to collect particulate phase nicotine. This microtube is follwed by a small Tenax sorbent bed to collect gas phase nicotine and 3‐ethenylpyridine. After sampling, the Teflon filter is transferred to a clean glass tube and the tube becomes an insert for a modified packed column injector port where the material collected on the filter is heat desorbed to a cold capillary tubing trap. Gas phase nicotine and 3‐ethenylpyridine are also transferred from the Tenax to the GC column by thermal desorption from the Tenax sorbent bed. Gas phase nicotine and 3‐ethenylpyridine, and particulate phase nicotine are each determined by GC analysis of the desorbed material. Nicotine and 3‐ethenylpyridine are quantitated by the use of external standards. This technique is straightforward and can be used for semi‐real time determination of both gas and particulate phase compounds in environmental tobacco smoke. The results obtained by this technique compare well with those obtained by sampling with annular diffusion denuders.
Determination of extracolumn effects in recycle gas chromatography with capillary columns
Authors: Roberts D. , Bertsch W.
Published: May 2005

Extracolumn band broadening in multidimensional systems utilizing flow switching is clearly undesirable. In certain cases, i.e. capillary recycle gas chromatography, the success of an experiment is contingent on the minimization of pre‐ and post‐column dispersion of the peaks. Knowledge of these sources of peak distortion is necessary to optimize the experimental design. A system that extracts statistical parameters from real chromatographic peaks is discussed and used to evaluate band broadening in a capillary recycle experiment.
The influence of evaporative dynamics on precision in split capillary GC
Authors: Bowermaster J.
Published: May 2005

The kinetics of sample evaporation was studied for four common injection liners at various temperatures. The rates of solvent and sample evaporation were measured. The sample distribution at the split point was probed by inserting two capillary columns in one injector. Greater homogeneity at the split point corresponded to higher precision (better correlation between the sample and internal standard peak areas). Evidence of aerosol formation using inverted cup inlet liners was seen. Packed column precision was better than capillary precision in each case, i.e., using straight split liners, inverted cup liners, and cold on‐column injection. Capillary precision is best when the sample and internal standard elute close together, and may be improved by using solvents that vaporize slowly.
Micro‐HPLC/TLC/FTIR
Authors: Fujimoto C. , Morita T. , Jinno K. , Shafer K. H.
Published: May 2005

Identification problems often encountered in high performance liquid chromatography (HPLC)/Fourier transform infrared spectrometry (FTIR) can be circumvented through the use of a thin‐layer chromatographic (TLC) plate as deposition and infra‐red sampling medium. The combination of complementary separation modes is shown to demonstrate increased resolution of the components of complex mixtures. In this particular work, the effluent from a reversed‐phase microcolumn is continuously deposited on a TLC plate with alumina stationary phase. The solute remains on the plate as a continuous record of the HPLC separation, which is then analyzed by diffuse reflectance FTIR. When the HPLC separation is inadequate for full separation of the components, the immobilized HPLC chromatogram serves as a starting point for subsequent TLC separation. A number of FTIR reconstructed chromatograms and spectra which are derived from the TLC plate aid in the interpretation.
High speed analysis of underivatized drugs by gas chromatography–mass spectrometry
Authors: Kokanovich J. D. , Simonick T. F. , Watts V. W.
Published: May 2005

The technique of choice for many types of forensic drug confirmations is gas chromatography/mass spectrometry (GC/MS). Significant amounts of analytical time can be involved in a GC/MS run. The use of a 0.1 mm i.d. fused silica capillary column with hydrogen carrier gas can significantly increase the speed of an analysis without sacrificing resolution. Nanogram levels of underivatized drugs, from amphetamine to strychnine, can be eluted in less than twelve minutes. The multitasking system permits data acquisition, while performing data reduction on the previous run.