bluuebunny/crossref_metadata_2025_split huggingface dataset:
Current technological challenges in capillary supercritical fluid chromatography
Authors: Lee M. L. , Markides K. E. 
Published: May 2005

AbstractIn 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

AbstractEffects 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

AbstractThe 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

AbstractIsotope 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

AbstractThe 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

AbstractThe 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

AbstractAnalysis 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

AbstractWe 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

AbstractThe 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

AbstractWhile 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

AbstractA 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

AbstractModification 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

AbstractDirect 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

AbstractA 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

AbstractOn 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.
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

AbstractSeveral 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

AbstractThe 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

AbstractNarrow‐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

AbstractA 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

AbstractFour 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

AbstractAromatic 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

AbstractFluorinated 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

AbstractAn 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

AbstractThree 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.
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

AbstractThe 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

AbstractThis 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

AbstractA 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.