Beata Polak

Application of a Horizontal DS Chamber to Planar Electrochromatography

A commercially available horizontal DS chamber has been applied to the planar electrochromatographic (PEC) separation of a dye mixture and of the enantiomers of dl-phenylalanine on non-polar stationary phases with ethanol—buffer or acetonitrile—buffer as mobile phases. The mobile phase was driven electroosmotically by applying a 50–250 V cm−1 field along a 10-cm RP18 TLC plate. Use of a counter-plate to the chromatographic plate enables elimination of problems associated with excessive delivery of mobile phase to the chromatographic adsorbent layer. Compared with conventional TLC separations the efficiency of electrochromatography was higher and the development time shorter.

Pressurized planar electrochromatographic separation of the enantiomers of tryptophan and valine

Pressurized planar electrochromatography (PPEC) with commercially available chiral plates has been used for separation of the enantiomers of tryptophan and valine. The effects on migration distance of polarization voltage, buffer pH and concentration, and the concentration of the organic component of the mobile phase have been investigated. Solute separation is compared for PPEC and conventional planar chromatography.

Pressurized planar electrochromatography.

Theoretical backgrounds, development, examples of separations, constructional details and principle of action of devices of pressurized planar electrochromatography (PPEC) are presented. Development of the mode is described in respect of operating variables (composition of the mobile phase, pressure exerted on adsorbent layer, mobile phase flow velocity, temperature of separating system, etc.) influencing separation efficiency (kinetic performance, repeatability, separation time). Advantages of PPEC such as high kinetic performance, short separation time and different separation selectivities, especially relative to conventional thin-layer chromatography, are described. Examples of two-dimensional separations are demonstrated to show high separation potential of the mode when combined with conventional thin-layer chromatography (TLC). The PPEC mode is in infancy stage of development, so its challenges are presented as well.

Lipophilicity of novel antitumour and analgesic active 8-aryl-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-dione derivatives determined by reversed-phase HPLC and computational methods

Eight novel antitumour and analgesic active 8-aryl-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-diones (1-8) have been obtained as a bioactive set of substances and their lipophilicity has been studied. The logk values of fifteen reference compounds and eight newly synthesised imidazotriazine-3,4-dione derivatives were determined by reversed-phase high performance liquid chromatography (RP-HPLC) using mixtures of methanol and water as mobile phases with different methanol concentrations. The relationships between logk values of a set of reference compounds (fifteen compounds) and investigated ones (eight compounds) and concentration of methanol was used for determination of the logkwater values by extrapolation. The partition coefficients (logP) values for reference compounds measured experimentally were taken from the literature. The calibration equation was then obtained for the standards of known lipophilicity (logPHPLC) and logkwater. In next step the partition coefficients of new synthesised solutes were calculated from the calibration equation. For the comparison purpose, additionally the partition coefficients (logPcalc.) of the examined imidazotriazine-3,4-diones were calculated by means of the Pallas 3.1.1.2. software. It was found that logkwater values as a lipophilicity measure of derivatives correlate well with partition coefficients measured experimentally (logPHPLC). Correlation between the logPHPLC and the logarithm of partition coefficient calculated by Pallas software (logPcalc.) is not so satisfactory as that for values determined experimentally. Furthermore, it has been found that the lipophilicity variation of investigated imidazotriazine-3,4-diones (1-8) correlates well with their acute toxicity expressed as log(1/LD50). The drug-likeness of all the bioactive 8-aryl-2,6,7,8-tetrahydroimidazo[2,1-c][1,2,4]triazine-3,4-diones was assessed on the basis of their structural properties by applying Lipniskis rule of five. The solutes have all four parameters important for the favourable pharmacokinetics in the human body that would make them likely orally active drugs in humans.

Computer-aided optimization of stepwise gradient profiles in thin-layer chromatography

SummaryTwo mixtures, one containing model coloured solutes and the other glycosides from the Digitalis species were separated by stepwise gradient thin-layer chromatography, the first in the system silica-toluene + ethyl acetate, the second in the system silica-ethyl acetate + methanol. The optimal gradient programs (i.e., for which maximal spread of spots along the plate is observed) were determined using a computer program reported in an earlier paper. Good separation and satisfactory agreement of predicted and experimental RF values were obtained; the non-aqueous system for the separation of lanatosides permits considerable shortening of elution time owing to the lower viscosity of ethyl acetate-methanol mixtures.

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

SummaryComplex 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.

Separation of amino acid 2,4-dinitrophenyl-5-l-valine amide diastereomeric derivatives with high-performance planar chromatography and pressurized planar electrochromatography

Separation of 2,4-dinitrophenyl-5-l-valine amide derivatives of some amino acids (leucine, isoleucine, valine, asparagine, cysteine, tryptophane) L and D-enantiomers with high-performance thin-layer chromatography (HPTLC) and pressurized planar electrochromatography (PPEC) is presented. The separation mechanism in the PPEC technique involves two effects (partition and electrophoresis) whereas HPTLC system employs only one (partition). The separation process in both modes was carried out with the HPTLC RP-18 plates. Influence of the aqueous-organic mobile phase composition (acetonitrile concentration, buffer type, its pH) on migration distance of the solute zones is investigated and compared for both techniques. The PPEC system turns out to be more sensitive to buffer type and pH than HPTLC one. Additionally, the electrophoretic effect is responsible for different separation selectivity in PPEC system in comparison to that in HPTLC one. The retention of DL-diastereoisomer derivatives of amino acids is stronger in comparison with its ll-antipodes for both separation techniques. The statistic evaluation of the migration distance in PPEC and TLC systems shows similar RSD.

The New TLC Method for Separation and Determination of Multicomponent Mixtures of Plant Extracts

The new mode of two-dimensional gradient thin layer chromatography (MGD-2D TLC) has been presented. Short distance development of sample in the first dimension leads to formation of the preconcentrated narrow zones. They are consecutively separated in the second dimension with the mobile phase gradient in several steps of development until the eluent reaches the further end of the chromatographic plate. The use of the above-mentioned technique allows isolating and then identifying the compounds of various polarity from the multicomponent mixture. The practical application of two-dimensional gradient thin layer chromatography has been performed for isolation of the two plant (Juniperus and Thymus) oils components as the examples of test mixtures. The experiments have been carried out with the use of silica gel plates as well as a normal phase condition. The results of solute separation with isocratic one-dimensional thin layer chromatography system have been compared with those of two-dimensional gradient system. It has been observed that application of the latter mode leads to almost triplicated number of zones in comparison with the former one. It is purposeful to apply the proposed mode to control the purity of the dominant component or components of the mixture.

Determination of the Lipophilicity of Some New Derivatives of Semicarbazide and 1,2,4-Triazol-5-one with Potential Antibacterial Activity

The chromatographic behavior of new derivatives of 1,2,4-triazol-5-one and semicarbazide was determined. The lipophilicity was confirmed by the use of a RP-TLC method. The partition coefficients were calculated by use of theoretical procedures. The correlation between theoretical and experimental lipophilicity was determined. All obtained compounds were tested for their antimicrobial activity. Graphical Abstract Determination of the Lipophilicity of Some New Derivatives of Semicarbazide and 1,2,4-Triazol-5-one with Potential Antibacterial Activity

Pressurized Planar Electrochromatography as a Supporting Tool for Qualitative Toxicological Chemical Analysis with Thin-Layer Chromatography and UV-VIS Spectrometry

ABSTRACT Pressurized planar electrochromatography (PPEC) was applied to support qualitative toxicological chemical analysis performed with thin-layer chromatography (TLC) and UV–Vis spectrometry. Based on retention/migration distance data of substances obtained in TLC and PPEC systems and database of their wavelength maxima of remission UV–Vis spectra as well, a combined fit factor was calculated for substance identification. The involvement of PPEC, TLC, and UV–Vis spectral data together in calculation of the combined fit factor lead to its lower values for substances, which were not identical with reference, in comparison with those when the combined fit factor was calculated using TLC and spectral data only. The results evidence that involvement of PPEC data in qualitative toxicological chemical analysis performed with TLC and UV–Vis spectrometry enhances reliability of it. GRAPHICAL ABSTRACT