Preparation and Potentiometric Study of Ranitidine Hydrochloride Selective Electrodes and Applications

Ranitidine hydrochloride selective electrodes were constructed based on ranitidine tetraiodo bismuthate (III) ion pair in PVC matrix membrane. The used plasticizers were di-butylphthalate (DBPH), di-octylphtalate (DOPH), di-butylphosphate (DBP) and tri-butylphosphate (TBP). The electrodes based on DOPH, DBP and TBP gave the same linear response in between 10 -5 and 10 -1 M, while the one based on DBPH ranged between 0.5·10 -5 and 10 -1 M. The slopes of the calibration curves were in between 22.25 and 41.20 mV per decade with correlation coefficients in between 0.9951 and 0.9990. The best detection limit was 6.30·10 -6 M for the DOPH electrode. The interferences of various cations and drugs were studied using the separate solution method. The optimum pH and lifespan of the electrodes were also studied. Ranitidine is a H 2 -receptor antagonist drug prescribed for the treatment of duodenal ulcer. A survey of current literature reveals that liquid chromatography, capillary electrophoresis and spectrophotometric methods have been reported for the determination of ranitidine hydrochloride in human plasma and commercial formulations (1-7). Electrochemical methods have an important part in biological and pharmaceutical analysis due to their simplicity, quickness and accuracy when compared to other analytical methods (8-13). Ion-selective electrodes (ISE) have enough selectivity towards the active substance over pharmaceutical excipients and they can be used for their quantitative analysis in pharmaceutical preparations without prior separations. Few studies have been reported for ranitidine hydrochloride quantitative analysis in pharmaceutical formulations based on ion-selective membrane electrodes only. Ion-selective membrane electrodes for ranitidine hydrochloride have been constructed based on ranitidine- tetrakis-(3-chlorophenyl)borate,ranitidine-tetraphenyl- borate and ranitidine-phosphotungstate as electroactive compound (14-16). We report in this paper the construction of several ranitidine hydrochloride electrodes based on tetra- iodobismutate (III) as ionophore using various plasticizers. The properties of those electrodes, the effect of pH, and the selectivity coefficient were studied. Experimental part Materials and methods All potentiometric measurements were carried out using a Hanna 301 digital pH/millivoltmeter. A ranitidine selective electrode was used as indicating electrode in conjunction with a Radelkis OP-0830P calomel electrode (SCE) as reference electrode. All used chemicals were analytical grade. Bismuth (III) subnitrate, potassium iodide, tetrahydrofuran (THF), di- butylphthalate (DBPH), di-octylphtalate (DOPH), di- butylphosphate (DBP) and tri-butylphosphate (TBP) were commercially available (Fluka). Polyvinylchloride (PVC) of relatively high molecular weight was used. Ranitidine