Fundamental studies in reversed-phase liquid-solid extraction of basic drugs; II: Hydrogen bonding effects

Anomalies in the elution order of the beta-blockers atenolol and propranolol on reversed-phase liquid-solid extraction cartridges have been studied. The hydrogen bond acceptor properties of the polar ring substituent in atenolol was found to result in greater retention than would be expected from the reversed-phase or cation-exchange mechanisms alone. This hydrogen bonding interaction could be attenuated by inclusion of a strong hydrogen bond acceptor in the eluent or more successfully by increasing the eluent water content. The conclusions from this work have been used to explain previously reported anomalies in the solid-phase extraction of polar basic drugs.