Plastic membrane electrode for the potentiometric determination of pethidine hydrochloride in pharmaceutical preparations

A novel poly(vinyl chloride) membrane electrode with dibutyl phthalate as p lasticizer based on the pethidine-tetraphenylborate ion-association complex as ion-exchange site for the determination of pethidine hydrochloride in i njections and tablets was developed. A linear response for 1 x 10(-5) to 1 x 10(-2) mol/L drug with a slope of 51.77 mV\decade was established. The op timum pH range was 2-8. The lower detection limit was 2.18 x 10(-6) mol/L. There were negligible interferences from a number of inorganic and organic cations and some common drug excipients. The electrode proposed had been su ccessfully applied to determine pethidine hydrochloride in tablets and inje ctions. The results correlated well with those obtained by the United State s Pharmacopoeia standard procedure.