Cetylpyridinium–iodomercurate PVC membrane ion selective electrode for the determination of cetylpyridinium cation in Ezafluor mouth wash and as a detector for some potentiometric titrations

A potentiometric method is described for the determination of cetylpyridinium (CP) cation using a polyvinyl chloride powder (PVC) membrane sensor based on CP–iodomercurate ion pair as an electroactive material. The sensor shows a linear response for CP ion over the concentration range of 2×10−6–1×10−3 M at 25°C. The electrode posses a sub-Nernstian slope of 29.0±0.4 mV decade−1, which has been thoroughly discussed.The electrode shows a fast potential response of ∼50 s, which is almost constant over a pH range of 3.0–6.0. Selectivity coefficient data for some common ions show negligible interference, however, cetyltrimethylammonium bromide (CTMAB) interferes significantly. An average recovery of 98.8% for CP with an average relative standard deviation (R.S.D.) of 1.2% has been achieved. The determination of CPC in Ezafluor mouth wash gave result that compare favorably with those obtained by the British Pharmacopoeia method. The CP electrode has been utilized as an end point indicator electrode in potentiometric titration of some anions, and applied for the determination of anionic surfactants in some commercial detergents and waste water.