EFFECT OF STATIONARY PHASE-STRUCTURE ON RETENTION AND SELECTIVITY OF RESTRICTED-ACCESS REVERSED-PHASE PACKING MATERIALS

Various restricted-access reversed-phase (RARP) packing materials. including alkyl-, alkyl ether- and alkylamide-type stationary phases, were compared with a commercially available peptide-bonded internal surface reversed-phase material and a shielded-type RARP material, Alkyl-type RARP materials were found to be more hydrophobic than ether or amide-type phases, which in turn were more hydrophobic than the materials commercially available at present. The contribution of polar as well as ionic groups in the stationary phase structure to retention selectivity was noted with some materials. The advantages of having a variety of RARP materials in terms of retention and selectivity were shown for separation of various drugs with a limited range of mobile phases.