Effect of the silica support of bonded reversed-phase columns on chromatography of some antibiotic compounds

Abstract

Chromatographic behavior of three types of antibiotics was investigated on bonded C 18 and polymeric reversed-phase columns. With penicillins with carboxylic acid functions only, retention and separations on the two types of columns were similar. β-Lactam antibiotics with basic functions did not give as sharp peaks on the C 18 column unless a silanol blocking agent, tetramethyl ammonium chloride (TMA) was added. In 0.01 M orthophosphoric acid-acetonitrile, tetracyclines were separated on the polymeric reversed-phase columns, but not on the C 18 columns. With addition of TMA, results on C 18 and polymeric reversed-phase columns were nearly identical. Addition of an ion pair also improved separations on the C 18 columns, but not as much as TMA. Interaction with the silica support of C 18 columns was used to separate tylosin from interferences in extracts of biological materials. The results demonstrate the importance of interactions with the silica support in chromatography of basic antibiotics on C 18 packings. These interactions can be either beneficial or detrimental to separations, depending on the conditions used.