The sulfide microsensor for dissolved H2S is a Clark-type microsensor, and it is the first reliable microsensor for measuring the products of sulfate reduction. H2S diffusing through the silicone membrane at the sensor tip is deprotonated in the alkaline electrolyte. The response of the sensor relies on the oxidation of HS- to elemental sulfur on a platinum anode through a redox mediator [Fe(CN)6]3-. A platinum guard anode ensures low and stable zero-current.
The H2S microsensor is a useful tool in the investigation of sulfur cycles in sediments and biofilms. The microsensor is especially valuable for studying the influence of microbial sulfur metabolism on corrosion in pipelines.
For determining total [S2-], the pH of the investigated environment has to be determined because H2S is an acid:
[S2-tot] = [H2S]+[HS-]+[S2-]
pH micro gradients can be determined with a Unisense pH microelectrode.
References
Borum, J. et al. (2005) The potential role of plant oxygen and sulphide dynamics in die-off events of the tropical seagrass, Thalassia testudinum. Journal of Ecology 93: 148-158. PDF
Jeroschewski, P., Steuckart, C. and Kühl M (1996) An amperometric microsensor for the determination of H2S in aquatic environments. Anal. Chem. 68: 4351-4357.
