Sandwich Chamber Research Articles

Application of a modified high-performance thin-layer chromatographic-densitometric technique to evaluate tobacco smoke exposure of multiple sclerosis patients

Multiple sclerosis (MS) is a serious, one of the most common disorders of the nervous system and is still uncharted course and etiology. Modern medicine characterized MS as a disease of multifactorial, complex pathogenesis. The studies were designed to test some new dependencies and determine exposure to selected environmental factors, including passive and active smoking using separation techniques in biological materials sampled noninvasively. The aim of this research was to determine by high-performance thin-layer chromatography (HPTLC) with densito metry major nicotine metabolites in urine samples taken from people with multiple sclerosis in earlier described conditions, but using new version of sandwich chamber, allowing to achieve better separation results. Urine samples (28) were collected noninvasively from patients with multiple sclerosis living in the region of Upper Silesia, Poland. The control samples (21) came from healthy people — family and friends of people with MS. Including active and pa...

Thin-layer chromatographic chambers with small and zero gas volume

Since in traditional thin-layer chromatography (TLC) variants only volatile mobile phases are used, the separation process in the standard conditions can be reproducibly implemented only in closed chambers, given that the type of a chamber and the development technique have substantial influence on the obtained results. In the literature, unfortunately, insufficient attention has been paid to the analysis of the role of TLC chambers in the chromatographic process as well as to the analysis of these chambers design.In this review article, the history of appearance and development of S-chambers (sandwich chambers) of different types, as well as the features of the development process in the different variants of chambers of this type, are examined.The authors hope that this work will be of common interest and will promote the further development of this significant area of planar chromatography.

A new instrument for automated multiple development in thin-layer chromatography

A new AMD instrument made in our laboratory is described in this paper. The main advantages of the instrument are very low cost both of construction and in use. Compared with ascending development in conventional instruments, a laboratory-made horizontal sandwich chamber is used for development, and, with the help of a series of special accessories, no obvious mobile phase remains in the distributor after each step; this saves a large amount of solvent. All the components of the instrument are easy to obtain, so the average worker in a chemical laboratory could construct all the instrument except the control unit. An application of the instrument is described; the results obtained were satisfactory.

Densitometric Comparison of the Performance of Stahl‐Type and Sandwich‐Type Planar Chromatographic Chambers

Over the years, conventional Stahl‐type thin‐layer chromatography (TLC) chambers (i.e., N‐chambers) have attracted criticism for more than one reason. For example, practitioners have questioned the value of the time‐consuming procedure of saturating these chambers with mobile‐phase vapor, and those who focus on the theory of planar chromatography, have complained that the well‐known stepwise diminishing of the rate of capillary flow of the mobile phase in the ascending mode makes computational optimization of solute retention more difficult and less accurate than it could be at constant flow. Everybody also readily agrees that mobile phase consumption is much higher in N‐chambers than in sandwich chambers (S‐chambers). The economic superiority of S‐chambers cannot, however, be regarded as a decisive factor when it comes to making a choice of the TLC equipment, because physicochemical aspects of the chromatographic process are more important. In the work discussed in this paper, we compared the N‐type and S‐type chambers in terms of mobile phase flow rate, the R F values obtained, and the densitometrically established concentration profiles of the test analytes. For this comparison, we selected several phenyl‐substituted alcohols and acids, low‐activity adsorbents (cellulose powder and chromatographic paper), and low‐polarity solvents (n‐octane and decalin) as the components of the chromatographic systems investigated. The overall conclusion from the results obtained is that the physicochemical performance of the S‐chamber is comparable with that of the N‐chamber, and the only indisputable superiority of the S‐chamber is the more economical use of the mobile phases.

STRATEGY OF PREPARATIVE SEPARATION OF ORGANIC COMPOUNDS BY THIN-LAYER CHROMATOGRAPHIC METHODS

ABSTRACT The preparative layer chromatography discussed in this review has been presented to facilitate the choice of the most effective, selective, cheap, and simplest method for separation and isolation of small quantities of some mixture components. Therefore, apart from very effective forced-flow development methods, the possibilities and applications of very simple sandwich chambers ES and DS are discussed. Both forced-flow and continuous planar chromatography development may be considered as quasi column preparative chromatography, carried out on smaller scale. Numerous application examples are also cited in this paper.

Cascade multiplication of a 26-GeV electron shower in a lead plate-emulsion sandwich chamber

The electron-photon shower development in a lead plate-emulsion sandwich chamber with a total effective lead thickness of 3.5 radiation units was studied for an electron energy of 26 GeV. The experimental electron multiplication coefficient (Pexp=19.4±1.4) agrees with a theoretical value (Pcalcd=20.4) calculated with corrections for the particle scattering and absorption.

Improvement of separation in zonal preparative thin-layer chromatography by gradient elution

Complex extracts of the plants Azulan and Hemorigen were separated by zonal micropreparative thin-layer chromatography in sandwich chambers of the ES and DS type which permitted zonal application of large volumes of sample, without auxiliary equipment. Application from the edge of the layer, in the frontal chromatography mode, markedly improved the separation efficiency and capacity owing to displacement effects which narrow the initially broad zones. Further improvement of separation efficiency and purity of fractions, revealed by densitometry, was observed using stepwise gradient elution. This was confirmed by extraction of some of the separated fractions from the layer and rechromatography; the composition of these fractions were generally simpler than for the corresponding isocratic chromatograms.

Comparison of selectivity of silica and Florisil in the separation of natural pyranocoumarins

Natural pyranocoumarin standards were separated using thin layers of Florisil (magnesium silicate) or silica and a sandwich chamber. Binary and ternary solvents containing a polar modifier (diisopropyl ether, ethyl acetate, acetonitrile or 2-propanol) as a mobile phase were used. Based on the relationship between R M values and the concentration of polar in the eluent, the optimum conditions were chosen for the separation of the isomers (samidin and isosamidin or cis- and trans-khellactone) and pyranocoumarin components of plant extracts from teh fruits of Libanotis species. The correlation of retention parameters for silica and Florisil showed individual differences in selectivity.

Modification of a horizontal sandwich chamber for thin-layer chromatography

Modification of a horizontal sandwich chamber for thin-layer chromatography

Computer simulation and optimization of preparative thin-layer chromatography under conditions of isocratic and stepwise gradient elution

An equilibrium sandwich chamber for continuous thin-layer chromatography was used to study overloaded systems. Mixtures of two or three dyes were used as the model samples, and wide starting zones were formed (volume-overloaded systems). The movement of the zones was recorded during continuous elution. The effect of sample volume and the mode of development (isocratic or gradient) on the maximum separation yield was investigated. A computer program was developed for the calculation of the final RF values for the front and rear edges of the bands.

Gradient thin-layer chromatography of plant extracts

A modified Niederwieser chamber for stepwise gradient elution, consisting of a PTFE capillary to store the series of eluents and a horizontal glass sandwich chamber with a glass distributor was used for the chromatographic separation of complex plant extracts (Seboren, Hemorigen and Pectosol) used in therapy. Densitograms demonstrate markedly improved separations of the extracts in comparison to isocratic elution.

Stepwise gradient development in thin-layer chromatography : IV. Miniaturized generators for continuous and stepwise gradients

A miniaturized generator of continuous gradients for equilibrium sandwich chambers with a glass distributor is described. The gradient profile is controlled by the initial concentration of the weaker eluent and its initial volume and by the composition and rate of delivery of the stronger eluent. Stepwise gradients are generated by delivery of eluents of increasing concentration of the stronger solvent from reservoirs in accordance with the gradient programme. Comparison of densitograms of thin-layer chromatograms from isocratic and gradient elution (continuous or stepwise) showed the considerable improvement in separation under gradient elution conditions.

Migration off Zones off Test Dyes in Preparative Thin-Layer Chromatography: Stepwise Gradient Elution

Abstract Migration and separation of zones of four test dyes were recorded and compared for isocratic elution and five-step gradient elution in a sandwich chamber with a glass distributer. The maximal load capacity for full separation of all components of the sample was several times larger for stepwise gradient elution.

A Microcomputer Program for the Calculation of RFValues of Solutes in Stepwise Gradient Thin-Layer Chromatography

Abstract A microcomputer program (in BASIC, e.g., for SPECTRUM ZX+) is proposed for the calculation of final RF values obtained under conditions of stepwise gradient. After introduction of RF values of sample components obtained for several isocratic runs, the microcomputer calculates the RF values for any gradient program. Good agreement of calculated and experimental RF values was obtained. The stepwise gradient development was carried out using a sandwich chamber with a glass distributor; the eluent fractions according to a chosen stepwise program were introduced directly under the distributor with a micropipette.

Gradient thin-layer chromatography of coumarins and furocoumarins

Extracts of four umbelliferous plants containing coumarins and furocoumarins were chromatographed in sandwich chambers with a glass distributor. best separations were obtained for stepwise gradient elution in the concentration range of 2.5 to 15% ethyl acetate in chloroform. Seven eluent fractions with increasing ethyl acetate concentrations were introduced directly under the distributor of the sandwich chamber.

Stepwise gradient development in thin-layer chromatography : II. Two-dimensional gradients for complex mixtures

A modified technique of two-dimensional thin-layer chromatography using an equilibrium sandwich chamber with a glass distributer is described. The sample is introduced from the edge of the layer as a rectangular zone 1.5 cm long and developed using a stepwise gradient of eluent composition. After preconcentration of the rectangular spots in the second direction, the chromatogram is divided into four zones, each being developed in the second direction using eluents of solvent strengths suitable for the individual fractions. In the first stage the sample capacity is significantly increased and the separation of components having large differences in capacity factors is possible, being enhanced by strong displacement effects occurring under gradient conditions; in the second stage the preconcentration of the zones and adaptation of the solvent strength to the individual groups of solutes ensures the distribution of the components over the whole plate area. Owing to the greatly increased sample size, trace components can also be isolated from complex samples such as plant extracts.

On-line extraction and preconcentration of solid samples in equilibrium sandwich chambers for thin-layer chromatography : Analysis of ink from ball-point pens

On-line extraction and preconcentration of solid samples in equilibrium sandwich chambers for thin-layer chromatography : Analysis of ink from ball-point pens

Stepwise gradient development in thin-layer chromatography : I. Optimization of gradient program

The application of an equilibrium sandwich chamber with a glass distributer for stepwise gradient development in thin-layer chromatography is described. Six to ten fractions of the eluent having increasing concentrations of a polar modifier are programmed graphically and introduced directly under the distributer with a micropipette. A comparison of the gradient profile with the obtained chromatogram permits adjustment of the gradient program in order to improve the positions of the spots on the chromatogram. The technique is relatively simple and permits the use of multicomponent gradients; it is especially suitable for the separation of complex samples, e.g., plant extracts, including zonal micropreparative separation. It is possible to improve the spot separation in a fragment of the plate without changing the positions of the remaining well separated spots.

A Simple Device for Gradient Elution in Equilibrium Sandwich Chambers for Continuous Thin-Layer Chromatography

Abstract The separation efficiency of various thin-layer chromatographic techniques was investigated using a horizontal sandwich tank for continuous elution with a glass distributer. Complex extract of camomile flowers (Azulane) was used as the test mixture and the number of separated spots as the measure of efficiency. Best results were obtained when gradient elution with chloroform-ethyl acetate mixtures was applied, A simple miniaturized device without mechanical mixer was employed, the spontaneous mixing being enhanced by gravitational flow of the components and their association on the molecular level.

Formation and migration of zones in overloaded preparative liquid-solid chromatography

An equilibrium sandwich chamber for continuous thinlayer chromatography was used to study overloaded systems of the heptane + methylene chloride-silica type. Mixtures of two or three dyes were used as the model samples. Wide starting zones were formed using a glass distributor (frontal chromatography stage), then the movement of the zones was recorded during continuous elution. The effect of sample concentration and volume on the maximum separation yield was investigated. Band compression effects are illustrated for samples dissolved in solvents having a low eluent strength. Satisfactory analogy was found to separations in preparative column chromatography. Good separation yield was obtained for frontal + elution TLC: depending on the differences in the RF values of the components, 6–16 mg samples were completely separated on 0.5×100×75 mm layers containing ca. 1 g of silica.