bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of log k′ — solvent composition relationships in thinlayer and column chromatography for systems of the type: Silanized silica — water + methanol
Authors: Dzido T. , Soczewiński E.
Published: May 2005

Relationships between log k' values of polynuclear hydrocarbons and composition of water/methanol mixtures were determined for HPTLC on RP‐18 silica and for HPLC using RP‐2 silica. In spite of differences in the adsorbents used, a good correlation between HPLC and TLC parameters was found. In the TLC experiments, a sandwich tank with a modified solvent distributor was used.

It has been reported that thin‐layer chromatography is a good technique for the preliminary optimization of column chromatographic separations [1–5]. So far, the comparison of TLC and HPLC has been mainly restricted to silica as the adsorbent. Since TLC plates precoated with silanized adsorbents recently became commercially available, it seemed interesting to compare the chromatographic parameters obtained for the “reversed phase” systems with the two techniques (see also ref. 6).
The assay of antibiotics in pharmaceutical preparations using reverse‐phase HPLC
Authors: Bagon Kay R.
Published: May 2005

Chromatographic methods are presented for the determination of chloramphenicol, erythromycin, tyrothricin, nystatin, penicillin, streptomycin, sulphanilamides and nitrofurans, in some pharmaceutical formulations. The methods have been applied in routine analysis and are in general capable of distinguishing the main antibiotic from decomposition products and likely congeners.
A sampling system using sample vials for high‐temperature isothermal capillary gas chromatography
Authors: Evrard E. , Mercier M. , Bal M.
Published: May 2005

A novel sampling system for isothermal capillary gas chromatography of medium‐ or low‐volatility mixtures is described and test results are reported using flame ionization detection. The system features a loading and positioning chamber for glass vials which can carry a dilute sample in up to 0.2 ml of a volatile solvent. The output from the glass vaporization chamber is trapped onto a packed precolumn operated in the backflush mode. The analytes are further transferred over a wall‐coated capillary trap prior to isothermal capillary GLC. Repeat‐cycle operation of the sampling system requires 10 channels of a processor for time control over 5 solenoid valves and 3 static heaters. Preliminary results with long‐chain n‐alkanes in the submicrogram range showed no unwanted effects. The principal claim of the system is an improved rejection of non‐volatiles.
Vapor‐phase sampling
Authors: Jennings W. G.
Published: May 2005

Two new sample preparation procedures that produce solvent‐free extracts especially suitable for use with high resolution GC are described. One is based on Soxhlet extraction in a pressurized container that permits the use of liquid carbon dioxide as the extractant; the other utilizes refluxing difluorodichloro‐methane (Freon 12) to isolate entrained volatiles from gas streams.
A versatile all‐glass GC/MS interface for capillary columns
Authors: Schmid P. P. , Müller M. D. , Simon W.
Published: May 2005

A new all‐glass interface for GC/MS designed to fully exploit the potential of glass capillary columns is described. The system works in the open split mode and has high versatility with respect to column changing. It is especially suitable for mass spectrometers, which are not exclusively dedicated to GC/MS work. Two chromatograms illustrate the properties of the described interface.
Superoxes, high temperature universal phases in (GC)2
Authors: Sandra P. , Verzele M. , Verstappe M. , Verzele J.
Published: May 2005

Most of the common classes of organic compounds chromatograph normally on Superoxes. There is no tailing or adverse effect from excessively different activity different activity coefficients. Superoxes are therefore universal phases for gas chromatography. This is also expressed by a wide useful temperature range from ∼50° to ∼300°. High MW Superox‐4 has a MAOT about 20° higher than the lower MW Superox‐0.1. Several applications illustrating the versatility of Superox phases in (GC)2 are presented.
Advances in the preparation and evaluation of GC capillary columns
Authors: Verzele M. , Sandra P.
Published: May 2005

The preparation of (glass) capillary columns of high quality is still not without difficulties. Six problems in this context are highlighted. Column material choice(l), glass wall modification(2) and coating(3) are considered to have reached a satisfactory level. Deactivation(4) is still in a state of flux. Quantitation(5) is the least satisfactory aspect of capillary GC. Scope expansion(6) will be helped by the introduction of new phases of high thermal stability and by the adoption of solutions exclusively applicable to capillary GC.

Evaluation of (glass) capillary GC columns is a rapidly developing field. Hopefully the number and complexity of test or polarity mixtures will not expand much further and it will be possible to make a clear and generally acceptable choice.

The preparation and evaluation of ever‐improving capillary columns is important to an ever‐widening group of chromatographers. Our opinion on selected topics in this already vast field is summarized in the following overview.
Theory of GC2 — an unusual approach
Authors: Franzen J.
Published: May 2005

In contrast to traditional theoretical approaches by calculation of (nonexistent) theoretical plates, a unified theory of gas chromatography as given by a definition of the resolution analogue to methods in signal processing or spectroscopy using the well‐known Kovacz indices as fundamental scale. A derivation of the thusly defined resolution from basic physical principles yields very practical formulae for peak width, maximum load, substance flow in peak maximum, concentration of substance in the carrier gas and other interesting parameters in dependence of capillary diameter, capillary length, film thickness, carrier gas speed, viscosities etc. Diagrams show favourite conditions for detectors responding on absolute substance flow (e.g. FID) or on concentrations.
Special cooling system for the on‐column injector in capillary gas chromatography eliminating discrimination of sample compounds
Authors: Galli M. , Trestianu S. , Grob K.
Published: May 2005

On‐column injection into a hot gas chromatograph oven involves the danger that the bottom part of the needle is warmed up above the boiling point of the solvent in the sample. Consequently parts of the sample are evaporated out of the needle instead of being introduced as a liquid into the capillary column. This causes losses and hence discrimination of the less volatile parts of the sample which remain in the needle.

A technical solution is proposed using a system for cooling the capillary during the injection, down to the injection point in the oven.
A novel method of preparing of glass capillary columns: Low‐temperature plasma etching and polymerization
Authors: Masada Y. , Hashimoto K. , Inoue T. , Sumida Y. , Kishi T. , Suwa Y.
Published: May 2005

A novel method is described for the preparation of stable glass capillary columns (glass open tubular columns), including the etching and formation of a polymer film on the inner glass capillary surfaces. The approach used here is based on low‐temperature plasma etching and polymerization. Under the influence of a field of radio frequency discharge, low pressure gases of fluoric compounds, introduced into the glass capillary tube, generate excited fluorine radicals which etch the inner surface. The plasma of organosilicone monomer in the glass capillary yields a uniform polymerized film on the inner surface. The resultant material functions as a good stationary phase for glass capillary gas chromatography (GC2). The inner surfaces treated with such a plasma, can be studied by means of a scanning electron microscope (SEM). The flexibility of this method permits the use of various stationary phases and surface modification.
Stationary phases for gas chromatography; chemical stability of polysiloxanes
Authors: Venema A. , Ven L. G. J. v. d. , Steege H. v. d.
Published: May 2005

A number of polysiloxanes have been shown to be sensitive to acids when dissolved in chloroform.

At 26O°C polysiloxanes were found to degrade under the influence of several compounds used or produced during the preparation of glass capillary columns.
Profiles of volatile metabolites in biological fluids using capillary columns
Authors: Zlatkis A. , Poole C. F. , Brazell R. , Lee K. Y. , Singhawangcha S.
Published: May 2005

Nickel capillary columns coated with moderately polarstationary phases such as Witconol can be used for the separation of the organic volatile fraction from biological fluids. A “transevaporator” sampling technique for the collection of the organic volatiles on glass beads from as little as 5 to 500 μl of biological fluids (e.g. urine, serum, amniotic fluid, breast milk, saliva, etc.) is described. The organic volatiles are thermally desorbed from the glass beads into a short precolumn cooled in liquid nitrogen, which overcomes the problems associated with sample introduction onto narrow‐bore capillary columns. The application of the full analytical technique to problems associated with the early detection of disease is illustrated.
Extra‐column effects in multi‐dimensional switching systems (MDSS) — GC
Authors: Ševčik J. , Gerner T. H.
Published: May 2005

In 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

A 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

The 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

Quantitative 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

The 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

The 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

Both 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

A 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

Multilayer 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

Complicated 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.
Ion pair chromatography on reversed‐phase layers
Authors: Volkmann D.
Published: May 2005

The results of investigations with ion pair chromatography on RP2, RP8 and RP18 thin layers are described. Heptane sulphonic acid is used as ion pair former. The best results are achieved on RP18‐layers with the counter ion in the mobile phase.
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

The 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

The 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

Glass 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

Changes 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

The 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

The 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

A 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

A 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

The 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

The 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

The 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

Retention 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

The 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

The 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

Gas 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

A 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.
Theoretical determination of optimum composition of the binary mobile phase for distribution of substances in thin‐layer chromatography
Authors: Chojnacka G. , Różyło J. K. , Malinowska I.
Published: May 2005

The measure of the distribution of a mixture of substances in TLC with a binary mobile phase is expressed as ΔRM which represents the difference between the RM values of substances i and j on use of the binary solvent 1 + 2 as the mobile phase. The possibility of determining its maximum value at an optimum composition of the binary mobile phase is demonstrated in this paper. This value can calculated from experimental and theoretical functions RM1,2 = f(Φ1) of substance i and j. More simply, ΔRM can be calculated theoretically from easily measurable adsorption parameters of excess adsorption isotherms and from chromatographic parameters obtained for pure solvents. The ΔRM value calculated theoretically can be utilized in a pilot technique for determination of the optimum composition of the mobile phase in gradient liquid chromatography.
Direct injection on capillary columns for gas chromatography
Authors: Chauhan J. , Darbre A.
Published: May 2005

Discrimination may occur when injecting samples onto gas chromatography capillary columns, whereby peak areas for higher boiling point compounds are smaller than they should be compared to lower boiling compounds. This problem is most important in quantitative work on solutes having a wide range of volatility. An all‐glass inlet system was used. Injections were made with a 10‐μl syringe onto a column without and injection point heater and with the column oven about 20°C below the boiling point of the solvent used for the solutes. Discrimination did not occur in a range of C12 to C36 n‐alkanes.
Prediction of experimental parameters in combined isocratic and gradient elution reversed phase high performance liquid chromatography (RP‐HPLC) using acetonitrile as organic modifier
Authors: Molnar I.
Published: May 2005

The use of gradient elution in RP‐HPLC is increasing. Aqueous buffers, such as phosphate at pH 1.7, with acetonitrile as the organic modifier are particularly advantageous as eluents with linear elution strength (LES). In the isocratic mode, under the experimental conditions used, fairly good linearity exists between logk' and xB (x is the volume ratio of the organic modifier, i.e. acetonitrile) with a correlation coefficient of 0.9995. The relationship between isocratic and gradient elution parameters, such as xB, x (starting composition in gradient elution), m (slope of the linear gradient), is transparent and the parameters of interest can be predicted fairly accurately using simple equations. The proposed system could be used in elaboration of a general retention index system for organic molecules in RP‐HPLC.
Effect of film thickness and supercooling on the performance of cholesteryl cinnamate liquid crystal capillary columns
Authors: Heath R. R. , Jordan J. R. , Sonnet P. E.
Published: May 2005

Improved separations of the isomers of olefinic aliphatic insect pheromones were obtained on cholesteryl cinnamate glass capillary columns by operating in the supercooled temperature range of the liquid crystal. Capillary columns were prepared with varying film thickness of the stationary phase; choice of the correct film thickness ensured optimum retention for a wide range of compounds within the most effective temperature range of the liquid crystal. The deactivation procedures described made the liquid crystal columns suitable for separation of the geometric isomers of polar and nonpolar compounds.
Theory of reflectance measurements in quantitative evaluation in TLC and HPTLC. 1. Multilayer model of reflectance and transmittance
Authors: Ebel S. , Post P.
Published: May 2005

In the approach described in this paper, the layer of adsorbent is divided into n sublayers. The radiation density in each sublayer is given by the sum of the transmittance and the reflectance of the adjacent sublayers. Absorption of light by the layer or the substance will diminish this radiation density. Depending upon the factors of reflectance and transmittance some light will pass to the adjacent sublayers. Two polynomials are derived from this readily understood formulation to calculate the reflectance or the transmittance of a layer of finite thickness. The algorithms given describe the reflectance and transmittance encountered in practical measurements with large amounts of substance per spot, as well as with small amounts. There are no restrictions with respect to nonideal scattering or reflection by the adsorbent layer support.
A general framework for the measurement of band broadening properties of GC capillary columns
Authors: Smuts T. W. , Buys T. S. , du Toit T. G. , Du Toit J. W. , Torline P. A.
Published: May 2005

In the approach to the developement of a practical procedure for the evaluation of band broadening properties of gas capillary columns, the expression for the variance of a solute band is cast in a dimensionless form. This expression supplies the basis for a valid bench mark for column evaluation. Experimental results demonstrate the applicability of the method.
Dynamic headspace analysis of solid waste materials
Authors: Brazell R. S. , Maskarinec M. P.
Published: May 2005

A dynamic headspace stripping technique for the extraction of volatile organic compounds has been applied to a variety of solid and semisolid waste materials. A simple glass apparatus accommodates a wide range of sample sizes and allows for the volatiles to be stripped at elevated temperatures. Concentration on Tenax, followed by thermal desorption and analysis by fused silica capillary gas chromatography provides detailed information on the volatile content of waste samples of widely differing matrix composition.
Glass capillary column chromatography of mixed derivatives of primary prostaglandins, 6‐keto prostaglandin F1α and thromboxane B2
Authors: Roselló J. , Gelpi E. , Rigaud M. , Breton J. C.
Published: May 2005

This work describes the use of glass capillary columns (GCC) in the rapid concurrent analysis of primary prostaglandins (PGs) (e. g. PGE2, PGE2, PGF2α) and other functionally significant metabolites of arachidonic acid (AA) such as TXB2 and 6‐keto PGF1α. The use of a new multistep mixed derivatization approach that generates the methyl esters of n‐butylboronate, pentafluorobenzyloxime, trimethylsilyl ether derivatives of these compounds remarkably simplifies the GC profiling of the three main pathways of AA metabolism (PGs, thromboxane, and prostacyclin). Furthermore, isomeric species giving very similar or identical mass spectral patterns can be easily identified by their relative retention times on high efficiency capillary columns.
Capillary columns with immobilized stationary phases. Part 3: The basic influence of vinyl groups
Authors: Grob K. , Grob G.
Published: May 2005

This article presents a preliminary description of the influence exerted by vinyl groups on the process and on the result of immobilization. Vinyl groups may occur in the stationary phase (e. g. in SE‐54) or may be bound to the support surface by persilylation with divinyltetramethyldisilazane. In the first case they promote the crosslinking process in the stationary phase. In the second case bonding to the solid surface is intensified. We have observed that vinyl groups in both situations contribute with comparable efficiency to the final non‐extractability of the stationary phase. A further, yet entirely independent influence of surface‐bonded vinyl groups concerns the acidity of the column. Whereas regular persilylation produces slightly acidic columns, a substantial shift to basic column behavior is observed after persilylation with a vinyl‐containing reagent. The potential future importance of both kinds of influence is discussed.
Analysis of urine by liquid chromatography in the ion‐exchange or hydrophobic mode
Authors: Hanai T. , Hubert J.
Published: May 2005

The analysis of ultraviolet‐absorbing constituents in urine was undertaken by anion‐exchange and reversed‐phase liquid chromatography. A newly developed anion exchanger (TSK‐IEX540 DEAE) was used for ion‐exchange mode liquid chromatography and its high polarity and physical strength greatly reduced the analysis time. Up to 80 peaks were resolved within 30 min. Hydrophobicity values were used to predict the retention times of acids in reversed‐phase mode liquid chromatography.
Systematic and statistical errors in quantitative evaluation in TLC and HPTLC. 4. Linear calibration
Authors: Ebel S. , Geitz E. , Glaser E.
Published: May 2005

Analytical results are often obtained from reflectance or fluorescence measurements in TLC or HPTLC with the aid of calibration lines. Curve fitting may not be done by conventional least squares methods for both the independent and the dependent variables are erroneous; errors occur in the volumes spotted on to the plate and in the reflectance/fluorescence measurements. Therefore the sum of the squares of the distances to the calibration line has to be minimized instead of the squared sum of the errors of the dependent variable. The algorithms used are derived and explained. Implications of error propagation for the analytical result are also given.
GC resolution of various D, L‐amino acid derivatives on a chirasil‐pval capillary column
Authors: Abe I. , Izumi K. , Kuramoto S. , Musha S.
Published: May 2005

An enantiomeric mixture of amino acids is derivatized to give the respective N(O)‐perfluoroacyl alkyl esters which can be resolved directly by gas chromatography on a Chirasil‐Val capillary column. The retention times, resolution numbers, and elution order are reported.
Focused cryogenic trapping for dynamic headspace and pyrolytic analysis of polymers on a fused silica capillary column
Authors: Moncur James G. , Sharp Terry E. , Byrd Edward R.
Published: May 2005

Focused cryogenic trapping has been used to maximize the high resolution capabilities of fused silica capillary columns during dynamic headspace and pyrolytic polymer analyses. Mass spectrometric detection with data system recording/processing provide sensitive, selective, and rapid results. The techniques described herein demonstrate the power of both dynamic headspace and pyrolytic analyses for troubleshooting applications with complex industrial polymer products.
Investigation of the low temperature effect in normal phase micro high performance liquid chromatography
Authors: Jinno Kiyokatsu , Hirata Yokio
Published: May 2005

The low temperature effect has been investigated on a set of three different silica‐gel micro columns with FC‐78 as eluent. An open tubular micro glass capillary, a packed micro glass capillary, and a packed micro teflon column were examined. Temperature dependences of separation factors and theoretical plate numbers were determined. It appears that a decrease in column temperature improves chromatographic selectivity while column efficiency decreases. The compensation temperatures were determined for these systems. The results suggest that the retention mechanism operative in the low temperature range is almost the same as that in the normal temperature range. However, the mechanism differs from that of reversed phase systems.
Investigation of some modes of flat‐bed chromatography
Authors: Berezkin V. G. , Vinogradova R. G. , Rysiev O. A. , Chechevichkin V. N. , Romanov F. I.
Published: May 2005

A comparison of different chromatographic methods is presented: column liquid chromatography (CLC), thin layer chromatography (TLC), and continuous‐elution flat‐bed chromatography (CEFBC), which is in fact a combination of the first two methods. In CEFBC a sample is applied to a sorbent layer in a steady flow of eluent, and the components are detected directly on the layer, or immediately upon leaving it, during the separation process. It is shown that evaluation of the separation processes in CEFBC is best accomplished in terms of the parameters applicable in CLC. The reproducibility of the analytical results obtained by CEFBC is better than in the case of TLC by a factor of 6 to 10, and approaches that known for CLC.
On the statistical independence of various column contributions to band broadening. Part 2: The non‐equilibrium contribution predicted by a slow, statistically independent relaxation of concentrations
Authors: Nilsson Olle
Published: May 2005

The mass balance changes of Said's so‐called “stage” model, based on the movement of the mobile phase with mean velocity ū (=L/tm), are synchronized by introduction of the relaxation time of Giddings, tr=1/(km+ks) where km and ks are the general overall mass rate constants for sample transfer to and from the stationary phase, respectively. This makes the “stage” length equal to the true theoretical plate height, ΔL, related to the classical HETP contribution due to non‐equilibrium, H(α), according to the “discontinuous‐ΔL” relation

Here k= (tms − tm)/tm is the central moment‐based capacity ratio, L the column length, and σ2(α) the second moment contribution from the non‐equilibrium only. Correct application of the relaxation‐time model to chromatography requires that the real sample concentration in the stationary phase at a given position and time, Cs,l,t, is in a continuous equilibrium with the real sample concentration in the mobile phase, Cm,l+ΔL/2,t at that time displaced down the column by a distance

This leads to the classical HETP contribution

obtained from various other continuous models, which implies that ΔL is a good estimation of the true theoretical plate height.
Underivatized steroids on persilanized capillary columns with non‐vaporizing on‐column injection
Authors: Kovarich E. , Munari F.
Published: May 2005

Recent developments in the preparation of capillary columns by persilanization of the glass surfaces have resulted in highly inactive, heat‐stable columns. With this type of column certain steroid hormone classes can be analyzed without derivatization; these include the 17‐keto steroids, 11‐oxo compounds, estrogens, and progesterone metabolites. It has been found that good quantitative analysis calls for non‐vaporizing, on‐column injection, as normal vaporizing injection results in breakdown of thermolabile compounds such as estriol and 17‐OH progesterone metabolites. The gas chromatographic method described was used to obtain urinary steroid profiles.
Reversed‐phase high‐performance liquid chromatography of fatty acid methyl esters with particular reference to cyclopropenoic and cyclopropanoic acids
Authors: Bianchini J.‐P. , Ralaimanarivo A. , Gaydou E. M.
Published: May 2005

High performance liquid chromatography of saturated, monounsaturated, diunsaturated, triunsaturated, cyclopropenoic (malvalic and sterculic) and cyclopropanoic (cis‐8,9‐methylenehexadecanoic and dihydrosterculic) fatty acids was performed with their methyl esters. All separations were carried out with two types of reversed phase columns, the eluent consisting of an acetonitrile/water mixture. The effect of water was studied in the range 0–15%. The best separation was obtained with acetonitrile/water (85:15 v/v). Quantitative results indicated that the detection limits depended upon ultraviolet wavelength and in the present study were 4 ng of methyl sterculate and 125 ng of methyl dihydrosterculate at 195 nm.