Construction of an iopanoic acid ion-selective electrode and its application to pharmaceutical analysis

Abstract

An iopanoate-selective electrode with a liquid membrane consisting of a tetraoctylammonium–iopanoate ion pair dissolved in p-nitrocumene is described. The electrode exhibits a rapid and slightly sub-Nernstian response (53 mV decade^–1) to iopanoate concentrations ranging from 5 × 10^–5 to 5 × 10^–3 mol l^–1 at pH 12 (0.01 mol l^–1 NaOH). No serious interference from common ions and tablet excipients was found and the electrode was used for the direct assay of iopanoic acid tablets by means of the calibration graph technique. The results compared favourably with those given by the United States Pharmacopeia (USP) XXII titrimetric method which requires extraction of the drug with hot alcohol. The electrode was also used to study the complexation of iopanoate to β-cyclodextrin.