The cationic surfactants are primarily applied in fabric softeners, hair conditioners, and other hair preparations. Other applications of cationic surfactants include disinfectants and biocides, emulsifiers, wetting agents, and processing additives. Cationic surfactants usually have been determined by two-phase titration method [1] having the main disadvantage that the method cannot be applied to strongly colored or turbid samples. Another drawback of this method is the use of toxic organic chlorinated solvents. The use of ion-selective electrodes overcomes these limitations [2-3]. In this investigations a high sensitive liquid membrane type potentiometric sensor has been prepared, based on a new 1, 3-didecyl-2-methylimidazolium-tetraphenylborate as sensing ion-pair incorporated into the plasticized PVC-membrane and o-nitrophenyloctylether as plasticizer. The sensor exhibited positive linear nearly Nernstian response toward different cationic surfactants down to 10-6 mol L-1. The interfering effect of some selected inorganic and organic cations has been investigated too and expressed as potentiometric selectivity coefficients. The selectivity coefficients were determined by fitting of Nikolskii-Eisenman equation to the experimental data obtained by mixed solution method. The standard solution of sodium dodecylsulfate has been used as anionic titrant. The sensor was applied for potentiometric determination of cationic surfactants in pure and technical grade systems, and in some commercial products. The results were compared with those obtained with two-phase standard titration method

Chemistry