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

A potentiometric method is described for the determination of cetylpyridini um (CP) cation using a polyvinyl chloride powder (PVC) membrane sensor base d on CP-iodomercurate ion pair as an electroactive material. The sensor sho ws a linear response for CP ion over the concentration range of 2 x 10(-6)- 1 x 10(-3) M at 25 degreesC. The electrode posses a sub-Nernstian slope of 29.0 +/- 0.4 mV decade(-1), which has been thoroughly discussed. The electr ode shows a fast potential response of similar to 50 s, which is almost con stant over a pH range of 3.0-6.0. Selectivity coefficient data for some com mon ions show negligible interference, however, cetyltrimethylammonium brom ide (CTMAB) interferes significantly. An average recovery of 98.8% for CP w ith an average relative standard deviation (R.S.D.) of 1.2% has burn achiev ed. The determination of CPC in Ezafluor mouth wash gave result that compar e favorably with those obtained by the British Pharmacopoeia method. The CP electrode has been utilized as an end point indicator electrode in potenti ometric titration of some anions, and applied for the determination of anio nic surfactants in some commercial detergents and waste water. (C) 2000 Els evier Science B.V. All rights reserved.