bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractDiscrimination 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

AbstractThe 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

AbstractImproved 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

AbstractIn 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

AbstractIn 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

AbstractA 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

AbstractThis 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

AbstractThis 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

AbstractThe 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

AbstractAnalytical 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

AbstractAn 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

AbstractFocused 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractRecent 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

AbstractHigh 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.
Computer comparisons of variables in capillary gas chromatography
Authors: Ingraham D. F. , Shoemaker C. F. , Jennings W. 
Published: May 2005

AbstractA series of computer‐constructed van Deemter curves that permits evaluation of a number of variables in capillary gas chromatography is presented. The graphs permit the comparison of inter‐related parameters, including the choice of carrier gas (hydrogen vs helium vs nitrogen), column length (10‐100 m), column diameter (0.20, 0.25, 0.32, 0.4 mm), solute partition ratios (0‐10), and liquid phase film thickness (0.1, 0.25, 0.5, 1.0 μm). The curves are evaluated, both in terms of the relative magnitude of the optimum average linear carrier gas velocity, and in terms of the significance of the sharpness of the curve.
Oil spill identification by high‐speed HPLC
Authors: Grimalt J. , Albaigés J. 
Published: May 2005

AbstractThe use of high‐speed HPLC in oil spill identification problems has been evaluated in terms of analysis time and reliability. The aromatic fraction was analyzed by reverse‐phase chromatography on a 3 μm packing, with detection at 210 and 287 nm, in less than 20 minutes. The profiles exhibited by several Spanish and Middle East crude oils were differentiated by simple statistical parameters. The effect of environmental weathering on the samples has also been investigated. An Arabian light crude oil was still identifiable after four months' simulated marine weathering.
General applications of fused silica capillary column (FSCC) chromatography to the analysis of non‐priority pollutant organics in environmental samples
Authors: Hunt G. T. , Hoyt M. P. 
Published: May 2005

AbstractFurther applications of fused silica capillary columns (FSCC) to the analysis of environmental samples are presented. The chromatographic behavior (RT, RRT) of organic compounds of environmental significance not listed as Consent Decree Priority Pollutants is investigated on an SE‐54 FSCC. Retention indices (RRT) and mass spectral response factors (RF) are presented for a total of 28 compounds including a number of chloro‐ and nitro‐substituted anilines, alkylpyridines, and alkylquinoline derivatives. The direct application of the FSCC/MS interface to the analysis of these compounds in actual environmental samples is presented, including vent emissions from a fungicide manufacturing process, and contaminated soil and water samples from two metropolitan Boston construction sites.
Capiliary columns with immobilized stationary phases. Part 5: Determination of column bleeding; re‐silylation
Authors: Grob K. , Grob G. 
Published: May 2005

AbstractThe bleeding of apolar high temperature columns may well be the critical factor limiting their applicability for GC/MS‐coupling, and for high temperature analyses. Therefore, a bleeding determination procedure has been designed as a basis for a systematic approach to the production of low‐bleed columns. Re‐silylation is a traditional method of reducing column bleeding. Increased efficiency of re‐silylation becomes feasible with immoblized coatings. Experience gained so far shows that resilylation of immoblized coatings may indeed result in the expected strongly reduced bleed rates and in improved overall column quality. Re‐silylation may also contribute to column washing by enhancing the solubility of adsorbed contaminants.
Chromatographic performance of deuterated solvents in reversed phase micro high performance liquid chromatography
Authors: Jinno K. 
Published: May 2005

AbstractThe chromatographic performance of the deuterated solvents, CD3OD and D2O, has been investigated in reversed‐phase micro high performance liquid chromatography. The chromatographic performance of CD3OD is only slightly superior to that of CH3OH. However, the performance of D2 is significantly superior to that of H2O, separation of aromatics being improved by about 30%. D2 is a particularly powerful solvent for the separation iof deuterated and non‐deuterated compounds.
A simple procedure for evaluating the heterogeneity parameter and the ratio of molecular sizes of solute and solvent by using HPLC data
Authors: Dawidowicz A. , Jaroniec M. 
Published: May 2005

AbstractBased on the relationship defining the dependence of the capacity ratio upon the composition of the mobile phase, a simple numerical procedure is proposed for evaluating the heterogeneity parameter and the ratio of molecular sizes of solute and solvent. This procedure is examined by using HPLC data for pesticides chromatographed in isooctane/dichloromethane eluent on Lichrosorb at 291 K.
Effect of viscosity on stationary phase stability in capillary column gas chromatography
Authors: Wright B. W. , Peaden P. A. , Lee M. L. 
Published: May 2005

AbstractWith recent advances in column technology it is now possible to prepare highly efficient, very inert, and thermally stable capillary columns coated with nonpolar polysiloxane stationary phases. Unfortunately, the same degree of success has not been achieved for some of the more polar polysiloxane phases. A parameter that has been studied little in the past in relation to stationary phase film stability is the viscosity of the stationary phase. In this paper the efficiency and stability of coated columns are correlated to the viscosity of the phase. Due to their structure, the viscosity of the phenyl‐containing polysiloxanes change rapidly with temperature and hence, thin‐film coatings are not stable at elevated temperatures. By using high viscosity phenyl‐containing methylphenylpolysiloxanes which were recently synthesized, efficient and stable columns have been prepared.
Determination of cyclosporin A in blood and plasma by column switching‐HPLC after rapid sample preparation
Authors: Nussbaumer K. , Niederberger W. , Keller H. P. 
Published: May 2005

AbstractA method for the determination of cyclosporin A in human whole blood and plasma is described which uses liquid chromatography with step gradient elution and a column switching technique. The chromatographic conditions chosen allow simple and rapid sample preparation, so that a result can be obtained within one hour. Blood and plasma are deproteinized with diluted methanol and an aliquot of the clear supernatant is directly injected. The detection limit for cyclosporin A is about 20 ng/ml starting from a 0.5 ml sample. The method is sensitive enough for monitoring the drug in the therapeutic range.
The use of chemically bonded stationary phases in thin‐layer chromatography‐a survey
Authors: Th. Brinkman U. A. , de Vries G. 
Published: May 2005

AbstractAn overview is given of the literature publisned in the field of thin‐layer chromatography on chemically bonded phases. Aspects which merit further attention are: quantitative analysis, organic solvent selection, stationary phase characteristics, surface modification of precoated silica plates, ion‐pair chromatography and correlation of thin‐layer and column chromatographic data.