Preparation and Potentiometric Study of Ranitidine Hydrochloride Selective Electrodes and Applications

Ranitidine hydrochloride selective electrodes were constructed based on ranitidine tetraiodo bismuthate (III) Electrochemical methods have an important part in biological and pharmaceutical analysis due to their simplicity, quickness and accuracy when compared to other analytical methods 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 ranitidinetetrakis-(3-chlorophenyl)borate,ranitidine-tetraphenylborate and ranitidine-phosphotungstate as electroactive compound [14] We report in this paper the construction of several ranitidine hydrochloride electrodes based on tetraiodobismutate (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), dibutylphthalate (DBPH), di-octylphtalate (DOPH), dibutylphosphate (DBP) and tri-butylphosphate (TBP) were commercially available (Fluka). Polyvinylchloride (PVC) of relatively high molecular weight was used. Ranitidine * email: [email protected] hydrochloride reference substance was purchased from Dar Al Dawa-Jordan. All pharmaceutical formulations were purchased from a local pharmaceutical company. There were prepared 10 -1 M stock solutions for each of the following substances: NH 4 Cl, NaCl, CaCl 2 , MgCl 2 , AlCl 3 , chlorpheniramine maleate, nizatidine, famotidine, vitamin B 1 and citric acid. Dilute solutions were prepared by subsequent dilution of those stock solutions. Potassium tetraiodobismutate (III) solution was prepared by mixing a potassium iodide solution with bismuth (III) subnitrate solution in hydrochloric acid medium For the synthesis of the ion pair complex, 0.1 g ranitidine hydrochloride was dissolved in 100 mL water, the pH was adjusted to 1.0 with 2 M hydrochloric acid and lastly the potassium tetraiodobismutate (III) solution was added in small portions with stirring. The resulting precipitate, ranitidine-tetraiodobismutate (III), was separated using a G4 filtering crucible; it was then washed with saturated solution of the precipitate and dried at 60°C. Construction of the electrode Several membrane compositions were investigated by varying the ratio of PVC, plasticizer, and the membrane active material A mixture was prepared by dissolving 1 mg of ranitidinetetraiodobismutate (III), 31 mg of PVC and 68.0 mg of plasticizer in 3 mL of tetrahydrofuran. The mixture was poured into a 30 mm diameter glass ring placed on a glass plate, and allowed to evaporate for 24 h at room temperature. The membrane obtained as 0.25-0.35 mm thick film was removed from the glass plate, and a 10 mm diameter disk was cut out and fixed to the end of a 100 mm long PVC tube by using a PVC/THF solution. The Ag/ AgCl electrode and 10 -3 M ranitidine hydrochloride solution were used as reference electrode and internal filling solution for the electrode, respectively