Amperometric sulfur dioxide gas sensor with dimethyl sulfoxide as solvent for internal electrolyte solution

An amperometric sensor for atmospheric sulfur dioxide based on a classical three-electrode cell configuration equipped with a microporous Teflon membrane is presented. The measured current, directly associated with oxidation of SO2 on a gold electrode, is related to the SO2 level. Various electrolyte solutions, including aqueous H2SO4, HClO4, HClO4-H2SO4 mixtures and Li2SO4 and also solutions of H2SO4 and HClO4 in dimethyl sulfoxide (DMSO)-water solvent mixture, were tested, The high sensitivity, up to 45 nA ppm(-1) (0.9 mu A cm(-2) ppm(-1)) SO2, was achieved when the sensor was filled with 5 M H2SO4 in DMSO-H2O with an H2O:DMSO mode ratio of 2. The respective value for standard 5 M H2SO4 electrolyte solution was only 0.5 nA ppm(-1) SO2, The high sensitivity and advantages resulting from the use of an organic solvent (DMSO) are discussed.