NITRATE-SELECTIVE ELECTRODE WITH A CRYSTALLINE MEMBRANE

Several types of nitrate-selective electrodes (NO3--SE) have been reported [1-4]. The first were those with liquid membranes [2] comprised of an organic phase with an ion exchanger that was separated from the analyte by a semipermeable membrane or filter. Further attempts were made to fabricate NO3--SE based on ion exchangers incorporated into graphite pastes [5, 6]. Film electrodes employing a polyvinylchloride (PVC) matrix have been most widely used. The characteristics of NO3--SE based on tetradecylammonium nitrate [4, 7] are known over a wide range of [HNO3] and [KNO3] (10(-4)-6.2 M). These electrodes are highly selective in HNO3 solutions containing other acids. Modem film electrodes have a solid contact [8] that significantly improves their operational characteristics. Recently NO3--SE based on triallyloctylammonium and triallyldodecylammonium bromides in addition to quaternary phosphonium salts 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 important factor in fabricating new types of NO3--SE. Electrodes with membranes of nitrone nitrate precipitated on a filter [11] and of phosphate glasses and organic silver salts [12, 13] have been proposed. In the present article, a completely solid membrane for an NO3--SE that is based on silver diethyldithiocarbamate and chalcogenides is proposed.