Influence of Two Cyclodextrin HP-derivatives on Retention and Migration Distance of Some Isomers in High- Performance Thin-Layer Chromatography and Pressurized Planar Electrochromatography Systems with Non-polar Adsorbents

Abstract

Separation of several isomer groups, i.e. diastereomers such as quinine and quinidine, cinchonine and cinchonidine, R,S-1-(1-naphthyl)-ethanol, R,S-1-(2-naphthyl)-ethanol, and R,S-1,1’- binaphthyl-2,2’-diamine racemates by means of high-performance thin layer chromatography (HPTLC) as well as pressurized planar electrochromatography (PPEC) techniques and carried out with the use of HPTLC RP-2, HPTLC RP-8 and HPTLC RP-18W plates as well as the acetonitrile - buffer mobile phase with hydroxypropyl-β-cyclodextrin (HP- β-CD) or hydroxypropyl-γ-cyclodextrin (HP-γ- CD) as additives in the mobile phase is presented. The influence of such variables as HP-β-CD concentration in the mobile phase, type of the used adsorbent and dimension of cyclodextrin interior (HP-β-CD and HP-γ-CD) on the migration distance of the solute zones is investigated. It has been observed that an increase in the HP-β-CD concentration brings about an opposite effect in the compared techniques and retention of the solutes diminishes in HPTLC, whereas the migration distances of the majority of isomers decrease in PPEC. The type of applied HP-cyclodextrin has a stronger effect on the separation selectivity of compounds in the PPEC system in comparison with the HPTLC system. Since the isomer differentiation mechanism in the PPEC technique is possible due to the two effects (partition and electrophoresis), whereas the HPTLC system employs only partition, changes in the separation selectivity of solutes in both investigated systems are expected and the former system turns out to be better at distinguishing between enantiomers in the R,S-1-(1-naphthyl)-ethanol and R,S-1-(2-naphthyl)-ethanol mixtures in comparison with the HPTLC-system.