Marek Studziński

Some aspects of TLC in homogenous magnetic fields.

This article consists of two parts. First part is a short review about the role of magnetic phenomena in natural environment, human surroundings, and his activities such as science, engineering, and medicine. The second part of the article presents a set of experiments, their results, and data obtained in a static homogenous magnetic field, generated by a pair of permanent magnets and outside it. Adsorption chromatographic systems were investigated: as chromatographed substances - polyaromatic hydrocarbon (PAH), as stationary phase - silica gel 60, as monocomponent mobile phases - n-hexane, n-heptane, n-octane, and benzene were used and binary mobile phases n-hydrocarbons - benzene. Magnetic field influences retention and efficiency of investigated chromatographic systems. Experimental data analysis (RF, N) allows us to propose some explanations of the differences between experiment results performed in induced magnetic field and outside it, and in consequence on the changes in the interfacial phenomena induced by field presence.

The effect of a magnetic field on the retention of polyaromatic hydrocarbons in planar chromatography

The effect of a magnetic field on the planar chromatographic retention of some PAH has been investigated. The horizontal chamber was placed between two neodymium magnets and chromatograms were developed in the magnetic field created. The effect of the magnetic field was tested for single-component and binary mobile phases containing n-alkanes and aromatic hydrocarbons. PAH were used as solutes. The results obtained showed that magnetic fields can affect the retention and shape of the chromatographic bands of the solutes investigated. The effect depends on the type of mobile phase, the properties of the adsorbent layer and the mode of development of the chromatogram (development distance).

Retention and Separation Changes of Ternary and Quaternary Alkaloids from Chelidonium majus L. by TLC Under the Influence of External Magnetic Field

Thin layer techniques proved their usefulness in the analysis of plant extract material. Thanks to their low operation costs, high sample throughput and possibility to gather chromatographic data for the whole sample in a single act, they allowed to find, and in some cases identify, active ingredients often hidden in sophisticated plant extract matrices. It was also proved that the presence of a magnetic field changes the retention of some substances, and moreover changes the separation efficiency of chromatographic systems. In the presented experiment, retention, efficiency and separation abilities of TLC chromatographic systems for mixtures of alkaloids under the influence of magnetic field depending on inductivity of the magnetic field, the saturation of chromatographic chamber and quantity of chromatographed substances were investigated. The results obtained were tested on real plant extracts that revealed the ability of chromatography in a magnetic field for separation of ternary and quaternary alkaloids from Chelidonium majus L. Our experiments proved that the presence of magnetic field induction lines perpendicular to the chromatographic plate plane can influence the width and retention of chromatographed substances, and can be considered as a tool for separation adjustment of plant extracts containing ternary and quaternary alkaloids.

Changes of 1,2,4-triazole retention and lipophilicity descriptor values in RP-TLC and MLC—TLC systems in the presence of an external magnetic field

As it was shown in earlier experiments, magnetic field can influence various processes taking part in nature. One of them might be the permeation of chemical compounds across biological membranes. An excellent tool for investigations on that subject is chromatography. Basing on retention measurements performed using reversed-phase thin-layer chromatography (RP-TLC) and micellar liquid chromatography—thin-layer chromatography (MLC—TLC), descriptors of lipophilicity were calculated for the group of 1,2,4-triazole derivatives. The experiments were performed in moderate (≈0.4 T) magnetic field and simultaneously outside it. The analysis of the obtained data showed that the presence of an external static magnetic field can alternate the obtained descriptor values which allows to assume that the ability of passive permeation of the investigated substances across cellular membrane also changes. The intensity of changes depends on the structure of the chromatographed substance and the lipophilicity measurement method.

Magneto-Thin-Layer Chromatography as a Tool for the Analysis of Plant Extracts

As it was presented in our previous works, applying external magnetic field during chromatogram development results in changes of retention of chromatographed solutes which can be used for adjustment of their chromatographic behavior, in order to optimize the separation. In this paper, we would like to present the influence of application of external magnetic field during chromatogram development on thin-layer chromatography (TLC) and high-performance thin-layer chromatography (HPTLC) plates on separation of ingredients of plant extracts, which are multicomponent mixtures and are very difficult to separate under conventional chromatographic conditions.

Thin-layer chromatography in moderate strength magnetic fields

Magnetic field can influence some processes taking part in the solid-liquid interphase area. An excellent tool for the investigation of this phenomenon is thin-layer chromatography. In this experiment, the influence of magnetic field parallel with chromatogram development direction on retention and system efficiency was investigated. The application of superconducting magnet allowed for generating the adjustable magnetic field up to about 2 T and allowed for investigation on dependence between inductivity of the field and retention changes of the chosen polyaromatic hydrocarbons. The obtained results show that the presence of magnetic field alternates the interactions among all components of a chromatographic system. Thus, in order to predict substance retention and system efficiency changes induced by the presence of the field, more parameters than the force acting on chromatographed molecule must be taken into account.

Planar Electrochromatography and thin-layer chromatography of tropane alkaloids from Datura innoxia Mill. extract in pseudo-reversed-phase systems

In the presented paper, the influence of the static electric field on retention, and in consequence separation, of tropane alkaloids present in Datura innoxia Mill. extract was demonstrated. Thin-layer electrochromatography (ETLC) on initially dry layers was used as the investigation method. The results obtained by ETLC were compared with the data obtained in thin-layer chromatography (TLC) analogous systems. Pseudo-reversed-phase systems (stationary phase — silica gel, mobile phase buffer at different pH and methanol mixture with different content of the methanol) were used. The presence of the electric field influences the retention parameters of the investigated compounds. The influence depends on the pH of the buffered mobile phase, composition of the mobile phase, and turn of the electric field lines in relation to the mobile phase migration direction. In the mobile phase, in which some of the alkaloids are in the ionic form, the significant differences between retention in cathode side and anode side were observed due to electrophoretic migration of the solutes, so direction of the electric field lines can be one of the systems’ optimization factor. The experiment proves that full separation of the investigated mixture ingredients is possible in ETLC only.

Comparison of TLC and Different Micro TLC Techniques in Analysis of Tropane Alkaloids and Their Derivatives Mixture from Datura Inoxia Mill. Extract

Planar chromatography is a very useful tool for analysis of wide range of different mixtures. Thanks to its possibility for rapid separation of large number of samples simultaneously, low solvent consumption and ability to analyse rough material allow to receive precise and reliable results in short time and low cost. Miniaturization of planar techniques brings a lot of advantages, such as shortening distance and time of chromatogram development, and further lowering of solvent consumption. Besides, it often allows to improve separation parameters and raise efficiency of chromatographic system. In this paper, ability of analysis of tropane alkaloids mixture from Datura Inoxia Mill. extract using conventional TLC technique with five micro TLC techniques (short distance TLC, HPTLC, UTLC, OPLC and ETLC) in maximally closed chromatographic conditions was compared in order to present abilities of micro TLC techniques in plant material analysis.

EFFECT OF ORGANIC MODIFIER ON THE LIPOPHILICITY OF ANTIPROLIFERATIVE ACTIVE 4-(5-AMINO-1,3,4-THIADIAZOL-2-YL/BENZENE-1,3-DIOLS BY REVERSED-PHASE OVERPRESSURED LAYER CHROMATOGRAPHY

The retention behavior of compounds of antiproliferative activity from the 4-(5-amino-1,3,4-thiadiazol-2-yl)benzene-1,3-diols group by OPLC was investigated. RP-18 stationary phase and five different organic modifiers were used. In the case of ethanol as an organic solvent the highest concentration of water in the eluent can be applied. On the base of the linear relationship between the retention and the concentration of organic solvent, various lipophilicity descriptors were determined. Moderate correlations between the chromatographic parameters and the calculated log P values according to the Villar approach were found. The RMw parameters were compared with the antiproliferative activity of compounds against human cancer cell T47D (breast cancer) to find QSAR equations. The best results for ethanol as the organic solvent were found.

Thin-layer chromatography of some derivatives of 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles in magnetic field

In this study, an investigation on the effect of the magnetic field on interphase phenomena influencing chromatographic separation was performed using thin-layer chromatography method. The presence of perpendicular to plane of the plate and the direction of chromatogram development magnetic field influences the interaction among all components of the chromatographic system. In consequence, the retention and efficiency of the investigated compounds in the given system should be altered. In this article, the effect of the field presence regarding retention mechanism, distance of development, and particle size of stationary phase for chosen derivatives of 2-(2,4-dihydroxyphenyl))-1,3,4-thiadiazoles is being investigated. The alteration of each abovementioned parameter affects the retention change caused by the field. It was also observed that the retention changes depend also on the structure of the studied compound, which may be a useful information for investigations on properties of newly synthesized compounds.