title: PVC matrix membrane sensor for potentiometric determination of cetylpyridinium chloride.
abstract: 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 degrees 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 micrograms/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 micrograms/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.
authors.affiliation: Microanalytical Laboratory, Applied Organic Chemistry Department, National Research Center, Dokki, Cairo, Egypt.
authors.forename: G A
authors.initials: GA
authors.lastname: Mostafa
mesh_terms: D002594:Cetylpyridinium / Q000032:analysis*; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D008567:Membranes, Artificial; D009067:Mouthwashes / Q000032:analysis; D010968:Plasticizers; D011143:Polyvinyl Chloride; D011199:Potentiometry; D013501:Surface-Active Agents / Q000032:analysis*
chemical_list: D007202:Indicators and Reagents; D008567:Membranes, Artificial; D009067:Mouthwashes; D010968:Plasticizers; D013501:Surface-Active Agents; D011143:Polyvinyl Chloride; D002594:Cetylpyridinium