Sol-Gel Method for the Matrix of Chloride-Selective Membranes Doped with Tridodecylmethylammonium Chloride

An organic-inorganic hybrid sol-gel matrix was used as for tridodecylmethylammonium chloride (TDMAC), which is an ionopbore for chloride. The sol-gel precursor prepared by the reaction of (3-isocyanopropyl)triethoxysilane with 1,4-butanediol. On mixing with TDMAC, the sol-state precursor slowly gelled, to give a TDMAC-containing membrane. The performances of the sol-gel membrane-based electrodes were compared to of TDMAC-based poly(vinyl chloride) (PVC) membrane electrodes. Membranes with an optimum ratio of TDMAC:sol-gel precursor (0.1:3 by weight) showed very baseline potential. The response slope toward chloride was approximately 55 mV/decade between 10^-4 5 × 10^-1 M Cl^- at room temperature. Moreover, selectivity toward chloride over salicylate and other lipophilic anions was improved, deviating from the Hofmeister selectivity pattern which is observed in most dissociated charged carrier-based potentiometric membrane sensors. The selectivity coefficients measured by the separate solution method in 0.01 M MES buffer, pH 5.5, were log k_Cl,sal^pot = 0.6, log k_Cl,citrate^pot = -1.6, and log k_Cl,acetate^pot = -0.6.