COMPARISON OF THE RETENTION OF ORGANIC-ACIDS ON ALKYL AND ALKYLAMIDE CHEMICALLY BONDED PHASES

Retention of pyridine and indole carboxylic acids was studied on alkylamide bonded phases under reversed-phase conditions at 35 degrees C. The alkylamide phases were synthesized by a two-step process, in which an initial amino phase was prepared under environmentally isolated conditions and subsequently reacted with alkanoyl chlorides. The retention measurements were carried out using acetonitrile-water eluent at different volume compositions and different pH values. For the comparative purposes analogous retention data were collected for conventional octyl phases bonded to various silicas. A comparison of the retention data measured on alkyl and alkylamide packings have demonstrated that the later, polymeric or monomeric, are better for separating pyridine and indole carboxylic acids, The comparative analysis of the chromatographic systems studied suggests that retention of these acidic solutes on alkylamide phases is governed by a mixed partition-displacement and ion-exchange mechanism.