Mobile Phase Effects in the Reversed-Phase Liquid Chromatographic Separation of Coenzyme Q Homologs

The isocratic separation of five coenzyme Q homologs (CoQ6 to CoQ10) by non-aqueous reversed-phase liquid chromatography was investigated. Seven different binary mobile phases were examined in order to determine which produced optimal resolution between the first two homologs in a given analysis time. Only small variations (1.42 to 1.45) in α, the group selectivity for the homologous series, were noted for the mobile phases that utilized acetonitrile as weak solvent when the retention of CoQ10 was held constant. Larger variations were noted in plate counts among the various mobile phases and this factor, rather than selectivity, determined the optimal mobile phase. When the capacity factor (k′) of CoQ10 was fixed at 5, a methyl t-butyl ethenacetonitrile mobile phase gave the best resolution of those tested. All five coenzyme Q homologs could be baseline resolved in less than 3 min on a 250-mm C18 column (k′ of CoQ10 equal to 1.1) with a mobile phase containing greater proportions of methyl t-butyl ether.