Lidocaine-selective membrane electrodes and their applications in pharmaceutical analysis

Abstract

The construction of either liquid membrane and PVC matrix-type lidocaine ion-selective membrane electrodes and their use in the potentiometric determination of lidocaine in pharmaceutical preparations are described. The ion-pair complex of the lidocaine cation with dipicrylamine is easily extracted into 1,2-dichloroethane or nitrobenzene and the extracts are used as liquid ion-exchange membranes. A better electrode was obtained by using the ion-pair complex of the lidocaine cation with dinonylnaphthalenesulphonic acid embedded in a PVC matrix as the ion-exchange membrane. The calibration graph for the liquid-membrane electrode (nitrobenzene as solvent) shows a near-Nernstian response towards the lidocaine cation over the concentration range 10^–1–10^–4 M, and that for the PVC matrix membrane electrode is linear in the range 10^–1–3.2 × 10^–5 M. Both electrodes were successfully applied to the potentiometric determination of lidocaine in pharmaceutical preparations.