Air-gap sulfide sensor with super-nernstian response in the low concentration range

An air-gap sulfide sensor is presented which operates on the basis of selective extraction of H₂S from an acidified sample into a small alkaline electrolyte film containing the dicyanoargentate (I) complex. This complex is partly decomposed during the measurement by the absorbed sulfide, and the potential of a silver sulfide-based indicator electrode which is in direct contact only with the electrolyte, then depends on the sulfide concentration of the sample. Because of the extraction and dissociation equilibria, the sensor responds in the low sulfide concentration range with a slope four times larger than that of a normal sulfide electrode. The lower limit of linearity is 10^?8 mol l^?1, because sulfide accumulates in the electrolyte film.