Abstract − Analytical Sciences, 17(9), 1043 (2001).
PVC Matrix Membrane Sensor for Potentiometric Determination of Cetylpyridinium Chloride
Gamal A. E. MOSTAFA
Microanalytical Laboratory, Applied Organic Chemistry Department, National Research Center, Dokki, Cairo, Egypt
A novel cetylpyridinium chloride-selective membrane sensor consisting of cetylpyridinium-ferric thiocyanate ion pairs dispersed in a PVC matrix placticized with dioctylphthalate is described. The electrode shows a stable, near-Nernstian response for 1 x 10-3 - 1 x 10-6 mol l-1 cetylpyridinium chloride (CPC) at 25°C over the pH range 1 - 6 with a cationic slope of 57.5 ± 0.4. The lower detection limit is 8 x 10-7 mol l-1 and the response time is 30 - 60 s. Selectivity coefficients for CPC relative to a number of interfering substances were investigated. There is negligible interference from many cations, anions and pharmaceutical excipients; however, cetyltrimethylammonim bromide (CTMAB) interfered significantly. The determination of 0.5 - 350 ug/ml of CPC in aqueous solutions shows an average recovery of 98.5% and a mean relative standard deviation of 1.6% at 56.0 ug/ml. The direct determination of CPC in Ezafluor mouthwash gave results that compare favorably with those obtained by the British Pharmacopoeia method. Precipitation titrations involving CPC as titrant are monitored with a CP sensor. The CP electrode has been utilized as an end point indicator electrode for the determination of anionic surfactants in some commercial detergents.
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