Potentiometric determination of penicillins with ion-selective electrodes.

Quaternary ammonium, phosphonium and arsonium membrane electrodes sensitive to benzylpenicillin, ampicillin and oxacillin have been investigated. The order of merit of electrode performance is cetyltrioctylammonium > cetyltrioctylphosphonium > cetyltrioctylarsonium. The electrodes are suggested for use in rapid determination of penicillin drugs by direct potentiometry.