In-situ measurement of the dissolved S2− in seafloor diffuse flow system: sensor preparation and calibration

Abstract

The preparation approach and calibration result of an improved type of ion selective electrode (ISE), which is used to measure the total dissolved S2−, are introduced in this paper. The improved Ag/Ag2S electrode uses silver wire as the substrate, which is surrounded by electric polymer containing superfine silver powder. After the stabilization of the epoxy-resin, Ag2S layer was formed by chemical reaction with 0.2 mol/L (NH4)2S solution for 5 min. With Ag/AgCl as reference electrode, the Ag/Ag2S electrode can be used to measure dissolved S2−. The correlation between the measured potentials and the logarithm of dissolved S2− is found to be linear, within range of the concentration of dissolved S2− from 10−2∼10−7 mol/L. The slope of the regression line between measured potential and logarithm of dissolved S2− is about −27.7, which agrees well with the theoretical Nernst value −29.6. Furthermore, the performance of the improved Ag/Ag2S electrode, such as the response time, sensitivity and stability, greatly outweighs the conventional Ag/Ag2S electrode.