Construction and characteristics of polymer-membrane electrode for sulfate using epoxy matrix

Miniaturized polymer-membrane electrodes (PMEs) for sulfate were constructed by the use of epoxy resin matrix as a material of electrode membrane. The PME, which has the best characteristics among all constructed PMEs, consists of a silver paste coated copper wire as a center substrate and the coating layers of barium sulfate and epoxy matrix incorporating 45 wt% ion exchanger solution of nitrobenzene containing 10 - 2 M tris- (1,10-phenanthroline) -iron (II) sulfate. The coating layers were formed on the substrate according to the order above with the thickness of (0.2~0.3) mm at each layer, so that the electrode was moulded in stick shape having about 1 mm outer diameter. The response of the PME were Nernstian for (5X 10-5~1.5x 10-2)M activities of sulfate. The noise of the PME on electrode potential was within db 0.5 mV. The allowable concentration for inorganic monovalent anions as interferences, which give rise to 10% of error (= 3mV) on response potential, was(5.6X lO-5~1.05x 103)M when the sample contained 1.0x10-3M sulfate.