bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extra‐column effects in multi‐dimensional switching systems (MDSS) — GC
Authors: Ševčik J. , Gerner T. H. 
Published: May 2005

AbstractIn order to permit valveless MDSS operation and easy column change, the hardware designed contains several connections. These can give rise to extra‐column band broadening effects. In order to quantitate such effects, the packed‐capillary column configuration (without trap) was used. The band broadening caused by the connections was found to be small: 120 ms2. A more practical approach was used to check the performance of the trap (re‐injection) in the capillary‐trap‐capillary column configuration. Here the results obtained with re‐injection from the trap were compared with results obtained in transfer and heart‐cutting modes while the trap was heated. Re‐injection was tested with n‐alkanes ranging from n‐C6 to n‐C28. A starting peak width of 1.6 s was found.
Characteristics and performance of gas chromatographic detectors with glass capillary columns
Authors: Yang F. J. , Cram S. P. 
Published: May 2005

AbstractA comparison of the characteristics and Performance of the flame ionization, electron capture, and flame photometric detectors with capillary columns is described. Factors which may affect the limits of detection, linearity, chromatographic peak shape, and other detector performance characteristics are discussed and compared with the results of a model derived for the behavior of concentration and mass flow‐rate dependent chromatographic detectors used with capillary GC systems. Examples are given of highly complex and labile mixtures such as pesticide residues and products from coal hydrogenation.
Determination of the glass transition temperature of polystyrene, poly(vinyl chloride) and poly(methyl methacrylate) using gas chromatography
Authors: Abushihada A. M. , Shunbo F. E. , Al‐Hajjar F. , Al‐Sultan Y. Y. 
Published: May 2005

AbstractThe glass transition temperatures, Tg, of polystyrene, poly (vinyl chloride) and poly(methyI methacrylate) have been determined from gas chromatographic measurements using n‐hexane, n‐heptane, meta‐xylene and para‐xylene solvents. The glass transition temperatures were detected on the z‐shaped retention diagrams which were produced from the plot of the logarithm of the specific retention volumes of the above‐mentioned solvents against the reciprocal of temperature, i.e. log V vs. 1/T. The glass transition temperature is specified by the temperature where the slope of log V vs. 1/T changes abruptly. The observed glass transition temperature of polystyrene produced by this technique was found to be in good agreement with those produced by other techniques such as the differential scanning colorimeter.The industrial importance of the glass transition temperature, Tg, might be due to the dramatic changes in the physical properties of the polymer, such as hardness and elasticity, which take place in the vicinity of this temperature. However, perfectly crystalline polymers do not exhibit glass transitions, because their chains are incorporated in regions of three‐dimensional order, called crystallites. Completely amorphous polymers and semi‐crystalline polymers usually exhibit both glass transition and melting.
Quantitative evaluation of thin‐layer chromatograms. 1. The calculation of remission and transmission using multilayer models
Authors: Prošek M. , Medja A. , Kučan E. , Katič M. , Bano M. 
Published: May 2005

AbstractQuantitative evaluation of TLC by direct photometric scanning is a promising method, in view of the development of cheap microprocessors: soon instruments for digital scanning will be commercialy available. In this paper we describe a multilayer model which seems to be a good approximation for solving the radiation transfer equation in the case of layer models with a gradient in an inward direction. Changes of remitted and transmitted light, in cases where a band lies in different layers, are presented. Examples shown are: the absorbance profile of a chromatographed band in the direction of scanning is approximated to that of an isosceles triangle; the concentration of the band is uniform, e.g. 0.3 A. U.; the concentration of the band is changing from 0 to 2.0 A. U. These results will serve to set up the correct algorithms for digital scanning and simultaneous determination in TLC.
Correlations between chemical structure and k‐value in the TLC of epimeric 3‐ethinyl‐3‐cholestanoles
Authors: Berbalk H. , Eichinger K. , Schuster R. 
Published: May 2005

AbstractThe chromatographic behaviour of TLC on silica gel of 3 pairs of epimeric 3‐ethinyl‐3‐cholestanoles is described.It is found that the k‐values of this class of compounds are predominantly influenced by the stereochemical orientation of the hydroxyl group. 3‐Ethinyl‐3‐cholestanoles with β‐configuration of the hydroxyl group have larger k‐values than their α‐oriented epimers.
Pressure and flow changes in vaporizing GC injectors during injections and their impact on split ratio and discrimination of sample components
Authors: Grob K. , Neukom H. P. 
Published: May 2005

AbstractThe effect of pressure changes in the vaporizing GC injectors on the split ratio is investigated. It is shown that the true split ratio depends on a number of parameters and may strongly differ from the split ratio expected from the flows set before injection. Quantitation with split injection based on external standards has to be carried out very carefully (or should be replaced by the method with internal standard). The split ratio may strongly change during the splitting of the sample. There are a number of mechanisms causing some sample components to be retarded and hence to be split by a different ratio. The split injector is a device which still requires further development.
Twenty years of glass capillary columns. An empirical model for their preparation and properties
Authors: Grob K. 
Published: May 2005

AbstractBoth the invention of the capillary drawing machine and the preparation and successful use of the first glass capillary column were achieved by Desty and his group in 1959.This paper attempts to describe the glass capillary column in a general way, including the spreading of liquid phases of different polarity and solid surfaces with different chemical and geometrical structures, and surface activity (as a source of essential column characteristjcs such as film stability, adsorptive and catalytic activity, acidity, and thermostability). The model is entirely based on experimental evidence. It is shown that today's apolar columns may closely approach ideal performance, such as is conceivable at the present time, while a severe gap still exists between the actual and the ideal characteristics of polar columns. The problem lies in the necessity of using considerably active support surfaces for polar coatings, yielding columns with reduced upper temperature limits, and of restricted suitability concerning the nature of sample. It is hoped that progress in the field of surface roughening may produce an inert support which is wettable by polar phases.
The preparation of thick‐film glass capillary columns
Authors: Torline P. , du Plessis G. , Schnautz N. , Thompson J. C. 
Published: May 2005

AbstractA detailed method for the routine preparation of glass capillary columns is presented. The method consists of coating a glass tube with quartz powder prior to pulling the tube into a capillary. The inner surface of the capillary consists of an even distribution of quartz particles fused to the walls. This surface has been found readily deactivated by standard procedures and ideal for the preparation of thick‐film glass capillary columns. The method has been thoroughly tested in two independent laboratories to ensure that the procedures described are reproducible.
Quantitative evaluation of thin‐layer chromatograms. 2. Experimentally confirmed calculations of multilayer models
Authors: Prošek M. , Medja A. , Kučan E. , Katič M. , Bano M. 
Published: May 2005

AbstractMultilayer models of different materials were prepared and scanned. Experimental measurements are compared with mathematically predicted values. This comparison leads to a further development of multilayer models. The advantage of using a white background on a scanning table for remission measurements was confirmed by calculation and experiment.
Automated glass capillary gas chromatographic analysis of PCB and organochlorine pesticide residues in agricultural products
Authors: Th. Tuinstra L. G. M. , Traag W. A. 
Published: May 2005

AbstractComplicated PCB mixtures can be separated in individual compounds using glass capillary gas chromatography, (GC)2. Depending on extraction and clean‐up procedure it is also possible to separate and determine organochlorine pesticides at the same time.This (GC)2 technique can be used to determine the contents of individual chlorinated biphenyls in milk products and animal feedstuffs and in the analysis of complicated extracts of soil and vegetable material.Practical aspects concerning connection of the capillary, automatic splitless injection, repeatability of the retention time, quality of the column with respect to separation and adsorption and degradation of DDT are discussed.The detection of individual chlorinated biphenyls is possible at the ppb level in fats and vegetable materials, using an extraction and clean‐up procedure, based on saponification of the sample.Preliminary results for milk, obtained from several areas, are shown.
Parameters influencing theoretical determination of RM‐values of naphthalene derivatives in thin‐layer chromatography by using binary mobile phase
Authors: Różyło J. K. , Malinowska I. , Gross J. 
Published: May 2005

AbstractThe purpose of the studies being carried out is to find some regularities of a general character which determine the relationship between the structures of the chromatographed substances and the composition of the mobile phase, i.e., between the log of the partition coefficient of the sample (Az), the K1‐values which characterize the adsorption equilibrium of component “1” in a given chromatographic system, the structures of the mobile phase components and the structures of the substances being chromatographed. This paper deals with the relationship between the Az and K1 parameters and the structure of naphthalene and a number of its derivatives. It has been shown that there is a close relationship between the kind, size, frequency and site of the substituent on the one hand and the Az and K1 values on the other. In order to eliminate the possibility of unwanted side effects, the investigations were carried exclusively using non‐active binary mobile phases of the type N + N or N + /B/. From these investigations, a comparison between the parameter Az and the surface of adsorbed molecules (As) was also possible.
High temperature (GC)2 and (GC)2/CI‐MS of nucleosides: Analysis of purinyl nucleoside isomer composition
Authors: Fischer P. , Lösch G. R. , Müller D. 
Published: May 2005

AbstractThe analysis of low‐volatile polar nucleosides by (GC)2/FID and (GC)2/CI‐MS, employing HMDS‐deactivated glass capillary columns and on‐column injection, is described. The four linkage isomers of a specific nucleoside, formed in the synthetic procedure, are in each case sufficiently well separated in the chromatogram; GC/CI‐MS allows for a differentiation of N‐7 and N‐9 linkage isomers.
Gas chromatographic analysis of estrogens from pregnant mares' urine using glass capillary columns
Authors: Zweig J. S. , Roman R. , Hagerman W. B. , VandenHeuvel W. J. A. 
Published: May 2005

AbstractGlass capillary columns coated with OV‐225 and Silar 10C were used to analyze estrogens (as their trimethylsilyl derivatives) present in pregnant mares' urine. Such columns provide better resolution in a shorter time than the corresponding packed columns, as exemplified by the separation of estrone from equilin.
Quantitative evaluation of thin‐layer chromatograms. 3. The calculation of fluorescence using multilayer models
Authors: Prošek M. , Medja A. , Kučan E. , Katič M. , Bano M. 
Published: May 2005

AbstractChanges of fluorescence intensity at the far side (transmission) and near side (remission) in cases where a spot of a fluorogen lies in different sublayers are calculated using a multilayer model. Examples shown are: the relative intensity of fluorescence in the layer as a function of the absorption coefficient of a sorbent at the excitation wavelength; the relative intensity of fluorescence at the far and near sides of a TLC plate; the influence of using too broad a monochromatic filter at the emission side on the results of fluorescence measurements. Advantages of near‐side scanning of fluorescence compared to far‐side scanning are discussed. The most important source of errors in fluorodensitometric measurements is the effect of secondary chromatography.
The overload phenomenon in gas chromatography
Authors: Yabumoto K. , Ingraham D. F. , Jennings W. G. 
Published: May 2005

AbstractThe usual concepts of the dynamics of an overloaded solute band fail to explain several phenomena such as the typical “leading‐tail” shape and retention deviations exhibited by overloaded peaks, and why these defects are more commonly observed in short columns. These and other related deviations from theory can be rationalized by a non‐classical approach to the overloading phenomenon.
Experiments with capillary columns having unconventional cross‐sectional geometry
Authors: Sandra P. , Verzele M. 
Published: May 2005

AbstractThe potentials of unconventional capillary columns, e.g. flat, crinkled, whisker and helically coiled open‐tubular columns (HOT columns) were evaluated. In comparison to circular columns, no improvement in the column performance, when used under normal capillary GC circumstances, could be observed.
Modification of HPTLC‐plates by in situ chemical bonding with non‐polar and polar organosilanes
Authors: Ericsson Monica , Blomberg Lars G. 
Published: May 2005

AbstractA method has been developed for the preparation of modified silica plates for high performance thin‐layer chromatography (HPTLC). Some typical organosilanes were thus allowed to react in situ with the silica of Merck HPTLC‐plates. This method was found to be highly reproducible, simple and cheap. Non‐polar plates were prepared and compared with commercial plates from Merck, Whatman and Macherey‐Nagel. Modification with cyanodecyltrichlorosilane resulted in plates that showed good coverage, efficiency and low residual silica activity. Silica modified with a multifunctional silane has different properties in different organic solvents. It will appear to be non‐polar in a polar solvent and vice versa. New advantageous separation systems are thus made feasible by the presence of cyano groups on the plate.The utility of modified thin‐layer plates is demonstrated by the separation of some homologues of p‐hydroxybenzoic acid esters and of some polycyclic aromatic hydrocarbons.
High pressure liquid chromatography of standard and amniotic fluid phospholipids
Authors: Hsieh J. Y‐K. , Turcotte J. G. , Waraska J. , Warburton D. , Oh W. 
Published: May 2005

AbstractA method for the HPLC separation of phosphatidylglycerol (PG), phosphatidylinositol (PI), phosphatidylcholine (PC), and sphingomyelin (SPH) was achieved using five in‐series columns packed with LiChrosorb, Partisil, and μ‐Porasil adsorbents, a solvent mixture of chloroform/methanol/ammonium hydroxide (50 : 36 : 6.7, by volume), and a Pye LCM2 Moving Wire (FID) detector. The same phospholipid mixture was also separated using four μ‐Porasil columns with the same eluent and detector. The latter conditions were found to be suitable for the analysis of phospholipids obtained after centrifuging, extraction, and precipitation of surface‐active lipid components of patient amniotic fluid collected at amniocentesis section. The lecithin/sphingomyelin (L/S) ratios, determined by the HPLC method, correlated well with those determined by the TLC technique in four normal pregnancies, whereas results of shake tests did not correlate too well with L/S ratios determined by the above two chromatographic methods. Besides the lecithin/sphingomyelin ratio, the present method was able to supply additional information: the concentrations of phosphatidylglycerol and phosphatidylinositol, for prediction of fetal lung maturity, and the palmitic acid content of amniotic fluid phosphatidylcholine.
High performance thin‐layer chromatography of some sixteen‐membered ring macrolide antibiotics
Authors: Bens G. A. , Van den Bossche W. , De Moerloose P. 
Published: May 2005

AbstractThe use of HPTLC in the analysis of some sixteen‐membered ring macrolide antibiotices was examined. In the case of Spiramycins, instrumentalized HPTLC proved to be very efficient for the separation and determination of these antibiotics. With the use of an internal standard together with the datapair technique in sampling and evaluation of the HPTLC plates, a coefficient of variation less than 1.5% could be achieved when determining the different Spiramycins. Other sixteen‐membered macrolides, such as Tylosins, Turimycins and 9‐Propionylmaridomycins can be separated with sufficient resolution for quantitative work, in spite of their extremely simular structures and large molecular weights. Detection is always at wavelengths which agree with the intrinsic absorption maximum of the chromophors of the components (e. g. 282 nm for Tylosins, 232 nm for Spiramycins and Turimycins, 195 nm for 9‐Propionylmaridomycins).
The effect of temperature and pressure on the retention time in series‐coupled gas‐chromatographic columns
Authors: Buys T. S. , Smuts T. W. 
Published: May 2005

AbstractThe promising technique of controlling chromatographic selectivity by the adjustment of individual column temperatures in systems of series‐coupled columns is investigated by means of a general model incorporating the effects of temperature and mobile phase compressibility. Expressions are derived for the linear flow velocity, the effective partition coefficient and the retention time for a system of n columns assuming an ideal mobile phase gas, under conditions of constant overall pressure drop and neglect of the temperature dependence of the mobile phase viscosity. The results indicate the importance of thermodynamic parameters, relative to parameters influencing the linear flow velocity, in determining the effect of temperature on the chromatographic retention time. Numerical results are illustrated graphically for two‐column systems which are discussed in greater detail. Switching of columns is also discussed and it is shown that even if thermodynamic contributions remain unchanged, non‐thermodynamic contributions have a notice‐able effect.
A selection method for high performance stationary phases in glass capillary GC. Part 1: The molecular weight distribution of polyglycol phases
Authors: Vigh G. Y. , Bartha Á. , Hlavay J. 
Published: May 2005

AbstractThe width of the molecular weight distribution (MWD) of polymer stationary phases influences their polarity and other gas chromatographic characteristics. The MWD of the most frequently used polyglycol‐type stationary phases such as Carbowax, Ucon, Emulphor and Pluronic has been determined and compared. The MWD determined by gel chromatography allows for the characterization of the actual batch of a stationary phase, provides a check on its consistency and helps to screen out the apparently less promising phases.
GC behaviour of symmetrical n‐dialkyl sulphides under isothermal and temperature programming conditions
Authors: Zotov L. N. , Golovkin G. V. , Golovnya R. V. 
Published: May 2005

AbstractRetention indices were determined for a homologous series of n‐dialkyl sulphides on three stationary phases (SE‐30, OV‐17 and XE‐60) under isothermal and linear temperature programming conditions. Under these two different GC conditions, equations were derived for each of the three stationary phases which showed the dependence of retention index on the number of carbon atoms and the boiling points for a homologous series of n‐dialkyl sulphides. The equation for the correlation isothermal retention index was shown to be applicable to the identification of n‐dialkyl sulphides using linear temperature programming. It was found that the GC behaviour of n‐dialkyl sulphides makes these compounds suitable for use as a standard series instead of n‐alkanes for the calculation of retention indices in GC analysis in which detectors insensitive to n‐alkanes are employed. The use of the homologous series of n‐dialkyl sulphides for the calculation of sulphide retention indices can be great practical importance in the microanalysis of natural compounds. We have used this method successfully in the analysis of pesticides containing S‐atoms.
Trace analysis of fungicides in grape juice and wine using glass capillary gas chromatography
Authors: Spitzer T. , Nickless G. 
Published: May 2005

AbstractThe fungicides Bupirimate, Fenarimol, and Vinclozolin were sprayed on Vines. The fruits were harvested 8 and 21 days after the final application and processed to juice and wine. The fungicide residues were determined by filtration of the samples throug XAD‐2 after pH adjustment, elution with methylene chloride, and glass capillary gas chromatography with SE‐30 as stationary phase. Residue values of the three compounds were reported before and after fermentation. The precision of the analytical method was established by spiking portuguese white wine and spanish grape juice with the three fungicides and Triadimefon. The recoveries were in the range 80%‐100%, except for Vinclozolin.
Fused silica capillary GC separation of alkene halohydrins
Authors: Geigert J. , Wadsworth J. , Moreland M. 
Published: May 2005

AbstractThe use of a fused silica capillary column for the gas chromatographic analysis of alkene halohydrin positional isomers is described. This method is illustrated with the complete resolution of the positional isomers for propylene bromohydrin, propylene iodohydrin, and allyl bromide bromohydrin. Comparison with the resolution obtained on a packed column is also provided.
Detection of PAH of molecular weight between 300 and 402 in airborne particulate matter by fused silica capillary GC and GC/MS
Authors: Romanowski T. , Funcke W. , König J. , Balfanz E. 
Published: May 2005

AbstractGas chromatography (GC), low‐voltage mass spectrometry (LV MS), and gas chromatography/mass spectrometry (GC/MS) have been used for detecting polycyclic aromatic hydrocarbons (PAH) of molecular weight between 300 and 402 in airborne particulate matter. Nearly 200 high molecular PAH separated by fused silica capillary columns could be characterized by their El mass spectra. The lack of reference substances precluded further structure elucidation.
Gas‐liquid chromatography of amino acids: Columns and methodology as a basis for routine amino acid analysis using glass capillary gas chromatography
Authors: Moodie I. M. , Burger J. 
Published: May 2005

AbstractA carefully Standardized technique is described for the preparation of glass capillary columns which can be used successfully for routine quantitative amino acid analysis. Comparison is made between two different modes of sample injection. Preliminary quantitative results from “split” injection and “on‐column” injection techniques are evaluated statistically and it is concluded that the “on‐column” system is a prerequisite for quantitative amino acid analysis by glass capillary gas chromatography. An analysis of fish muscle protein hydrolyzate illustrates an application of this technique and results are compared with those from a packed column analysis.