Nitrate-sensitive corroding metal electrode

Abstract

The electrode potential of Devarda's alloy in phosphate solutions buffered at pH = 12 containing different amounts of nitrate ions has been measured. A proportional relation between the electrode potential and the concentration of nitrate ions [NO 3 −] is observed when [NO 3 −] is less than 40 mg 1 −1. When [NO 3 −] is larger than 200 mg 1 −1, log[NO 3 −] is linearly related to the electrode potential, with a slope of about 120 mV decade −1 up to [NO 3 −]=10 000 mg 1 −1. The presence of chloride sulfate and perchlorate ions has almost no effect on the above relations. The sensitivity and selectivity of the above metal electrode exceed those of nitrate-ion-selective electrodes. Since the electrical impedance of the corroding metal/solution interface is much lower than that of other methods, the potential measurement should be easier.