bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of metabolites relating to the tryptophan‐NAD pathway in rat urine by cellulose high performance thin‐layer chromatography
Authors: Yamada M. , Minami Y. , Yuyama S. , Suzuki T. 
Published: May 2005

AbstractHigh performance thin‐layer chromatography (HPTLC) was used to determine 12 metabolites of the tryptophan‐NAD pathway in rat urine. The method of separation described in the previous report was improved. The metabolites were separated on the cellulose plate by using five multiple developments with four solvent systems. The plate was scanned by the TLC scanner at 254 nm and the amounts of the metabolites were calculated by comparing peak areas of the scanning curves obtained for the urine sample and for the authentic standards. This procedure can be used as a semiquantitative determination method for the metabolites in biological fluids.
Sequential centrifugal layer chromatography (SCLC): A New technique for the isolation of natural compounds. Part 1: Description of the method and practical aspects
Authors: Nyiredy Sz. , Erdelmeier C. A. J. , Sticher O. 
Published: May 2005

AbstractSequential centrifugal layer chromatography (SCLC), a new preparative planar separation technique, combines the advantages of preparative centrifugal layer chromatography (CLC) and analytical, horizontal, anticircular, and sequential thin‐layer chromatography (TLC). In this on‐line preparative method, solvent delivery is locally and temporally variable, which means that the mobile phase can be brought onto the plate at any desired place.The SCLC apparatus operates in two modes: circular, with the help of centrifugal force in an inclined position, and anticircular, by means of capillary action in a horizontal position. These two operation modes can be combined and repeated as often as required, hence the separation space becomes practically unlimited. In this way the capacity and separation performance is significantly increased.In the present paper the apparatus and the method are described and some practical aspects are mentioned.
Quantitative HPTLC analysis of carboxylic acids in wine and juice
Authors: Lin L. , Tanner H. 
Published: May 2005

AbstractThe need for quick and specific assay of carboxylic acids in wine and non‐fermented beverages is explained. The method developed in this work is based on high performance thin‐layer chromatography (HPTLC) followed by densitometric evaluation. Untreated samples, with the exception of red wines which were destained, were directly sprayed onto the cellulose layer. The chromatogram was developed with ethyl acetate‐toluene‐water‐formic acid 60:20:20:15, then stained with xylose‐aniline reagent. Densitometric scanning is by absorbance at 546 nm. The method is quick, sensitive, and has a wide dynamic range for the acids analyzed.
Sequential centrifugal layer chromatography (SCLC): A new technique for the isolation of natural compounds. Part 2: Comparative study on centrifugal layer chromatography (CLC) and SCLC for the separation of furocoumarin isomers
Authors: Erdelmeier C. A. J. , Nyiredy Sz. , Sticher O. 
Published: May 2005

AbstractThe new sequential centrifugal layer chromatography extends the possibilities for preparative separation of furocoumarin isomers. In the present work, isobergapten, pimpinellin, bergapten, isopimpinellin, and sphondin were isolated from a prepurified extract of Heracleum sphondylium roots using two different techniques, namely, centrifugal layer chromatography (CLC) and sequential centrifugal layer chromatography (SCLC). The former technique was carried out with four plates, whereas the latter method required only one plate, using the same mobile phase in each case. A further advantage of the SCLC method was that all completely separated compounds could be quickly and efficiently eluted in small volumes of mehtanol.
Inorganic and organic mercury analysis by HPTLC and in situ densitometric detection. Application to real samples
Authors: Bruno P. , Caselli M. , Traini A. 
Published: May 2005

AbstractInorganic mercury and some organo‐mercury species have been separated as dithizonates by HPTLC and determined in situ at the subnanogram level by densitometric automatic scanning of the plate. The extraction efficiency of the dithizonates was tested at pH 1, 7, and 10. The Rf values for HgD, CH3HgD, C2H5HgD, and C6H5HgD are 0.15, 0.32, 0.35, and 0.28 respectively. The recovery of the tested mercury species in simulated and real samples has been investigated. Conditioning of the plates with NH3 prior to elution eliminates interference by many other metal ions. Some examples of real sample analysis (tap water, sea water, human urine) are reported.
Pneumatic pulse dampener for liquid chromatography
Authors: Gupta P. K. , Nikelly J. G. 
Published: May 2005

AbstractA simple pulse dampener is described for use with reciprocating pumps. The dampener may be assembled locally form readily available components and consists mainly of a small reservoir of compressed helium which acts as a cushion to dampen the mobile phase pulsations pneumatically. Depulsing is 99% complete and is uniform through a wide pressure range. The pneumatic dampener allows the use of single‐ piston reciprocating pumps in conjunction with highly flow‐sensitive detectors at their highest sensitivity settings.
Non‐aqueous ion exchange chromatography, an alternative to buffered silica gel
Authors: Rüedi P. 
Published: May 2005

AbstractA method is described for the HPLC separation of moderately acidic, dehydrated, and multi‐oxygenated diterpenoids, compounds which hitherto could not be handled by HPLC. It is based on chemically bonded silica strong cation exchangers in the protonated form, using organic solvents of the full polarity range as eluents. Thus a stable and easy‐to‐regenerate substitute for buffered silica gel is obtained.
Cold trap/reinjection interface for two‐dimensional gas chromatography
Authors: Hagman A. , Jacobsson S. 
Published: May 2005

AbstractThe construction and evaluation of an interface for two‐dimensional gas chromatography is described. The interface consists of commercially available components and is attachable to available gas chromatographs without any major modifications. The interface has been constructed so as to permit “heartcutting” as well as solute band concentration. Trapping is performed in a simple cold trap of fused silica. Flow switching is accomplished by Deans switching. Factors of the over‐all chromatographic performance are examined.
Multidimensional separation of isomeric species of chlorinated hydrocarbons such as PCB, PCDD, and PCDF
Authors: Schomburg G. , Husmann H. , Hübinger E. 
Published: May 2005

AbstractA multidimensional GC‐system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n‐alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set‐up, the live‐switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference‐free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so‐called “linear” indices.
Total steroid profiling with capillary GC. Details on sample preparation
Authors: Vanluchene E. , Vandekerckhove D. 
Published: May 2005

AbstractThe accuracy and reproducibility of steroid and steroid conjugate determinations using capillary GC are evaluated. It is possible to analyze many unconjugated steroids, steroid sulfates, and some steroid glucuronides simultaneously, simply by using group fractionation based on successive hydrolysis and solvent extraction steps. However, a reliable determination of corticosteroid glucuronides can only be obtained after previous isolation of the glucuronides as a group, with ion exchange chromatography. In complex chromatograms, the combined use of nitrogen specific detection and flame ionization detection facilitates peak identification.
FABES and FAPES – transesterification of triglycerides with higher alcohols. Quantitation and mass spectrometric evaluation
Authors: Traitler H. , Richli U. , Winter H. , Kappeler A. M. , Monnard C. 
Published: May 2005

AbstractIn order to facilitate the gas chromatographic determination of butyric as well as other short chain fatty acids, triglycerides containing these fatty acids were transbutylated and transpentylated to give FABES (fatty acid butyl esters) and FAPES (fatty acid pentyl esters), respectively. This method allows the molecular weight of the compounds to be increased while their polarity is decreased. Short chain esters elute sufficiently separated from the solvent; due to the decreased polarity, elution of long chain fatty acids is only slightly retarded compared to the corresponding methyl esters. Quantitative evaluation over a large series of injections proved the linearity of correction factors in both cases, FABES and FAPES, with a slight deviation for 16:0 and 18:0, respectively. Structural characterization was performed by GC/MS. It was shown that there are characterstic fragmentations for FABES as well as for FAPES. The El‐mass spectra give structural information about the alcohol and acid moieties, the ester molecule and the Cl‐spectra indicate the molecular weight. The absence of abundant highly characteristic peaks in the spectra of these esters makes the detection of FABES or FAPES in complex mixtures more difficult than the detection of FAMES with their very characteristic ions at m/z 74 and 87.
Analysis of polycyclic aromatic compounds in the fly ash of an incineration plant for radioactive waste
Authors: Tausch H. , Stehlik G. 
Published: May 2005

AbstractOrganic compounds adsorbed on fly ash from an incinerator for radioactive waste were investigated. Following Soxhlet extraction and concentration, analysis was performed by GC and GC/MS using high temperature silylated glass capillary columns coated with OV‐1 and SE‐54. Compound identification was based on retention data, relative detector responses, and mass spectra. Among other polycyclic aromatic compounds, series of gradually chlorinated PAHs containing four to seven aromatic rings were detected. For unequivocal identification, appropriate reference compounds were synthesized by chlorination of the corresponding parent PAHs.
Capillary supercritical fluid chromatography with simultaneous flame ionization and mass spectrometric detection
Authors: Holzer G. , Deluca S. , Voorhees K. J. 
Published: May 2005

AbstractA simple interface between a capillary supercritical fluid chromatograph and an Extranuclear Simulscan mass spectrometer is described. The SFC column is directly inserted into the ion source through the existing GC‐interface. The system is equipped with a splitting device which allows simultaneous EI/MS and flame ionization detection when CO2 is used as the supercritical phase. The effect of source temperature and pressure on CO2 clustering was studied for optimization of source conditions. The performance of the system was evaluated with a series of model compounds and standard mixtures.
Capillary gas chromatography and mass spectrometry detection of anabolic steroids II
Authors: Cartoni G. P. , Giarrusso A. , Ciardi M. , Rosati F. 
Published: May 2005

AbstractHigh resolution gas chromatography‐mass spectrometry has been used to detect anabolic steroids in urine. With fused silica capillary columns connected directly to mass spectrometer, the anabolic steroids could be detected after extraction, hydrolysis, and derivatization with a sensitivity better then 1 ppb. In vivo excretion and metabolism has been investigated for androstanolone, methandriol, oxymesterone, quindenione, and boldenone.
Conditions for accurate split injection of samples with wide boiling point range
Authors: Eyem J. 
Published: May 2005

AbstractThe effect of injection temperature, carrier gas flow rate, geometry of the glass insert, and column temperature program on the precision and accuracy of split injections was measured. Three types of injection techniques were compared: injection into a hot isothermal injector, isothermal injection with the injector at the solvent boiling point temperature, and programmed injection temperature. The last of these techniques produced the best accuracy and precision of analysis. Conditions for complete sample trapping at the beginning of programmed temperature analysis are described.
Optimization of selectivity using sequentially coupled capillary columns
Authors: Mayfield H. T. , Chesler S. N. 
Published: May 2005

AbstractThis investigation lays groundwork for the development of an optimization system for sequentially coupled capillary column systems. Three methods for calculating effective capacity factors were obtained from the literature and were tested to determine suitability for optimization use, using four test analytes and two dissimilar columns. This work concentrates on the development of a method for the estimation of optimum column temperatures in sequentially coupled systems.
Applications of a miniaturized fluorimetric photodiode array detector for capillary liquid chromatography
Authors: Gluckman J. C. , Novotny M. 
Published: May 2005

AbstractA high sensitivity, multichannel fluorescence detector with small volume has been developed for capillary column liquid chromatography. Using an intensified linear photodiode array to monitor fluorescence emission, several important mixtures exhibiting native fluorescence have been examined following high efficiency separation on a capillary column. By correlating mass spectral, fluorescence spectral, and retention time data, information of potential utility in the structural elucidation of aromatic molecules contained in complex mixtures can be obtained. Examples include the separation and spectral examination of the polyaromatic compounds in samples of both biological and environmental interest.
Selectivity and selectivity tuning in capillary gas chromatography
Authors: Sandra P. , David F. , Proot M. , Diricks G. , Verstappe M. , Verzele M. 
Published: May 2005

AbstractThe selection of stationary phases in capillary gas chromatography is discussed. Methyl silicone, phenyl methyl silicone, trifluoropropylmethyl silicone, biscyanopropyl silicone, and high molecular weight (HMW) polyethylene glycol are considered to be the basic phases. Selectivities and polarities between these phases are obtained by selectivity tuning. Selectivity tuning can be performed in three different ways, namely by synthesizing a tuned stationary phase, by mixing the basic phases, or by coupling capillary columns of different selectivities. In coupling capillary columns the variables are column length, β‐value, temperature, and/or pressure.
On‐line multidimensional chromatography using supercritical carbon dioxide
Authors: Christensen R. G. 
Published: May 2005

AbstractA two‐dimensional chromatographic separation is described which makes use of the unusual properties of supercritical carbon dioxide mobile phase. This solvent has the property of giving a separation of polycyclic aromatic hydrocarbons (PAH) on amine‐bonded columns similar to that given by usual normal‐phase solvents, and on octadecylsilane‐bonded columns similar to that given by usual reversed‐phase solvents.Packed columns were used, arranged so that they could be switched in or out of the solvent flow. Polycyclic aromatic hydrocarbon mixtures isolated from coal tar were fractionated according to number of aromatic carbon atoms on an amine‐bonded column, and these fractions were trapped on an octadecysilane‐bonded column. They were subsequently eluted according to the polarity of the individual compounds. Separations from fractions containing 16 and 18 aromatic carbon atoms are shown.
Identification of radicals spin‐trapped in autoxidized linoleic acids: A high performance liquid chromatography and electron spin resonance study
Authors: Evans J. C. , Rao K. R. N. , Jackson S. K. , Rowlands C. C. , Barratt M. D. 
Published: May 2005

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

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

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

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

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

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

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

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

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