Hydrophilic Interaction Planar Chromatography of Geometrical Isomers of Selected Co(Iii) Complexes

Abstract

The retention behavior of fourteen geometrically isomeric Co(III) complexes: three pairs of neutral facial-meridional (fac-mer) isomers, one pair of cis-trans isomeric complexes of neutral type, and three pairs of cationic cis-trans isomers have been investigated on thin-layer of silica gel. The effect of the composition of the mobile phases consisting of different ratios of water, methanol, and sodium chloride on retention of the complexes has been explored. In the broad range of mobile phase compositions, a successful separation of geometrical isomers was obtained. A retention order of isomeric complexes consistent with the mobile phase composition was found. The best resolution of isomers was achieved by using solvent systems containing 10 % water. On the basis of the results obtained, possible separation mechanisms were considered. Hydrophilic-interaction chromatography was assumed to be the mechanism determining separation in the case of mobile phases containing small amounts of both water and salt.