NITRATE-SELECTIVE ELECTRODE WITH A CRYSTALLINE MEMBRANE

Several types of nitrate-selective electrodes (NO3--SE) have been repo rted [1-4]. The first were those with liquid membranes [2] comprised o f an organic phase with an ion exchanger that was separated from the a nalyte by a semipermeable membrane or filter. Further attempts were ma de to fabricate NO3--SE based on ion exchangers incorporated into grap hite pastes [5, 6]. Film electrodes employing a polyvinylchloride (PVC ) matrix have been most widely used. The characteristics of NO3--SE ba sed on tetradecylammonium nitrate [4, 7] are known over a wide range o f [HNO3] and [KNO3] (10(-4)-6.2 M). These electrodes are highly select ive in HNO3 solutions containing other acids. Modem film electrodes ha ve a solid contact [8] that significantly improves their operational c haracteristics. Recently NO3--SE based on triallyloctylammonium and tr iallyldodecylammonium bromides in addition to quaternary phosphonium s alts have been proposed [9, 10]. Various compositions of acrylonitrile -butadiene polymers [9] or plastified PVCs [10] have been used as the membrane matrix. Developing solid ion-sensitive membranes is an import ant factor in fabricating new types of NO3--SE. Electrodes with membra nes of nitrone nitrate precipitated on a filter [11] and of phosphate glasses and organic silver salts [12, 13] have been proposed. In the p resent article, a completely solid membrane for an NO3--SE that is bas ed on silver diethyldithiocarbamate and chalcogenides is proposed.