Potentiometric determination of cetylpyridinium chloride using a new type of screen-printed ion selective electrodes.

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.

The potentiometric method based on surfactant ion-selective electrodes (SISEs) was broadly applied to ionic surfactants in solution due to the change in their activities, i.e., concentration in dilute solution, of both the counterions and ionic surfactants at the point of aggregation. The monomeric surfactant concentration can be determined by SISEs with almost no pretreatment, even if the sample solutions were colored or viscous. Ion-sensitive electrodes are usually used to investigate the dimerization, aggregation, and micelle formation of ionic surfactants in aqueous solution. By using SISEs, the binding isotherm of ionic surfactants bound to other materials such as polymers and biomolecules (DNA and proteins) can be calculated easily. According to the binding isotherms, the different binding and aggregation processes between ionic surfactants and other materials can be identified and characterized, which is important for understanding the interaction between ionic surfactants and polymers and/or biomolecules. Herein we present a comprehensive review of the literature devoted to SISEs used in the aggregation of surfactants in solution over the last two decades, looking back the developmental history of SISEs, reviewing the applications of SISEs in the studies of surfactant/surfactant mixtures, the adsorption of surfactants on polymers, including neutral polymers, polyelectrolytes, and biopolymers and the interactions between surfactants and lipid vesicles, etc., prospecting the new wave of SISEs.

Surfactant ion-selective electrodes: A promising approach to the study of the aggregation of ionic surfactants in solution

Experimental and theoretical study on cetylpyridinium dipicrylamide – A promising ion-exchanger for cetylpyridinium selective electrodes

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 × 10-3 - 1 × 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 × 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 µg/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 µg/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.

Raafat A. Farghali

Papers

Hexadecylpyridinium-phosphotungstate ion association in construction of a hexadecylpyridinium cation selective electrode