Authors:Adam Chomicki, Tadeusz H. Dzido, Ewa Materna-Witkowska and Anna Klimek-Turek
Thin-layer chromatography (TLC) and pressurized planar electrochromatography (PPEC) of amino acids in normal-phase system is presented. The results have been obtained for various normal-phase high-performance thin-layer chromatography (HPTLC) and PPEC systems with the mobile phase that comprised acetonitrile in the concentration ranges 40–90% and 20–90%, respectively, and HPTLC silica gel 60 F254s plates from Merck. The data obtained show differences in separation selectivity between HPTLC and PPEC systems. The respective separation selectivities have been obtained for HPTLC and PPEC systems with the mobile phase buffer pH in the range 2.6–9.0. The retention of amino acids in HPTLC systems has demonstrated minor dependence on buffer pH, while, in analogous PPEC systems, migration distances of the solutes have shown considerable changes. The differences of separation selectivity in HPTLC and PPEC systems are interpreted in terms of solute partition in the former and solute partition and electrophoresis in the latter.
Authors:Aneta Hałka-Grysińska, Radosław Ł. Gwarda, Krzysztof Pawełek, Tomasz Baj and Tadeusz H. Dzido
Satisfactory separation of a test mixture of 19 dyes with a general elution problem was obtained by reversed-phase stepwise gradient thin-layer chromatography with single void volume of the mobile phase. An effect of the supplementary mobile phase flux to the surface of the adsorbent layer, observed previously, was eliminated. This improves the flow profile of the mobile phase and the shape of spots, and increases the repeatability of the results within the same plate and between studies. The experimental values of the relative zone/spot position, Rpg, showed good correlation with the results predicted by the computing calculation.