Poly(vinyl chloride) matrix membrane electrodes for the selective determination of buformin

Abstract

Two poly(vinyl chloride) matrix membrane buformin-selective electrodes have been developed, for the direct determination of the buformin cation in aqueous solutions. These membrane electrodes are based on the use of ion-association complexes of the buformin hydrochloride cation with either tetraphenylborate (I) or 5-nitrobarbiturate (II) counter ions as ion-exchange sites. These electrodes show good selectivity for buformin hydrochloride over wide pH ranges (pH 4–9.5 for electrode I and pH 4–10 for electrode II) in the presence of some inorganic as well as organic cations. The two electrode systems exhibit a fast, stable Nernstian response in the ranges 10^–1–10^–4 mol l^–1 and 10^–1–10^–5 mol l^–1 for I and II, respectively. The direct potentiometric determinations of buformin hydrochloride in aqueous solutions using electrodes I and II at concentration levels as low as 38.7 or 5.2 µg ml^–1, respectively, were found to be accurate. The membranes withstood storage for up to 3 months in the dry state.