Sol-gel method for the matrix of chloride-selective membranes doped with tridodecylmethylammonium chloride

An organic-inorganic hybrid sol-gel matrix was used as host for tridodecylmethylammonium chloride (TDMAC), which is an ionophore for chloride. The sol-gel precursor was 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 those 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 stable baseline potential, The response slope toward chloride was approximately 55 mV/decade between 10(-4) and 5 x 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.