Thiocyanate ion selective coated-wire electrode using a rapid-cure type epoxy resin adhesive as the sensing membrane

Abstract

Coated-wire membrane electrodes for thiocyanate ion were developed by using commercial epoxy resin adhesive (rapid-cure type) as the sensing material membrane. The electrode structure is as follows. Electrode(1): silver/epoxy resin adhesive (epoxy resin: curing agent=1:1) membrane. Electrode(2): silver/silver iodide-polyvinylchloride type adhesive (AgI:90%) membrane/epoxy resin adhesive membrane. Electrode(3): silver/silver iodide (containing 0.5% potassium iodide)-polyvinylchloride adhesive membrane/epoxy resin adhesive membrane. It was found that the three electrodes showed the Nernstian response to thiocyanate at ion concentrations from 10^-4 M to 10^-1 M in 10^-1 M disodium hydrogenphosphate. The variation of pH has no effect on the electrode potential over the range of pH 4 to 10 at thiocyanate ion concentrations from 10^-3 M to 10^-1 M. The order of the selectivity coefficients (K_ij) for electrode (2) is as follows: Cl^-_??_ClO₄^->I^->NO₃^-_??_S^2-_??_Br^-_??_CN^-_??_ClO₃^->CH₃COO^-_??_CO₃^2-_??_BF₄^-_??_Fe(CN)₆^4-_??_S₂O₃^2-_??_CrO₄^2-_??_C₂O₄^2-_??_SO₄^2-Selectivity coefficients of the three electrodes for the anions investigated were less than 0.5.