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.