H2S microsensor

dissolved & atmospheric hydrogen sulfide


The Unisense hydrogen sulfide (H2S) microsensor is an excellent research tool for high quality sulfide measurements.

The microsensor can be made with tip sizes of only 2-3 µm allowing for non-destructive measurements of H2S at high spatial resolution in numerous applications. The response time can be less than 3 seconds and the H2S microsensor has an insignificant H2S consumption giving you fast and accurate H2S measurements.

In combination with the Unisense pH micro-electrode, the Unisense H2S microsensor can also measure total sulfides.

The Unisense oxygen microsensor has been used by the world’s leading scientists for decades and is cited in over hundreds of papers in journals such as Nature and Science.


  • Measurement tip size as small as 2 µm
  • Extremely fast T90 response times of less than 3 seconds
  • Suitable for a wide range of applications from biogeochemistry to biomedical


detailed information

PageLines-UnisenseOX-MR.jpgThe Unisense H2S microsensor is a miniaturized amperometric sensor with an internal reference, a sensing and a guard anode. The anodes are polarized against an internal reference. Driven by the external partial pressure, H2S from the environment penetrates through the sensor tip membrane into the alkaline electrolyte, where the HS ions formed are oxidized immediately by ferricyanide, producing sulfur and ferrocyanide.

The sensor signal is generated by re-oxidation of ferrocyanide at the anode in the tip of the sensor (Jeroschewski et al. 1996). The resulting sensor signal is in the pA range and is measured by a high quality picoammeter e.g. the Unisense Microsensor Multimeter. The internal guard electrode is polarized to scavenge H2S and facilitates  a constant ratio of ferri- to ferrocyanide in the electrolyte, thus minimizing the zero-current.

To calculate total sulfide concentrations, it is also required to measure the pH in the sample.


tip diameter sizes
  • H2S-10: 8-12 µm
  • H2S-25: 20-30 µm
  • H2S-50: 40-60 µm
  • H2S-100: 90-110 µm
  • H2S-500: 400-600 µm
  • H2S-MR: 400-600 µm
  • H2S-N: 1.1 mm
  • H2S-NP: 1.6 mm – needle sensor for piercing
  • H2S-Eddy: 15-25 µm





Jeroschewski,P. et al (1996), An Amperometric Microsensor for the Determination of H2S in Aquatic Environments, Anal Chem, 4351 – 4357, vol. 68

Stachowitsch,M. et al (2007), Oxygen depletion and benthic mortalities: the first in situ experimental approach to documenting an elusive phenomenon, Limnology and Oceanography: Methods, 344 – 352, vol. 5

Mohanakrishnan,J. et al (2008), Nitrite effectively inhibits sulfide and methane production in a laboratory scale sewer reactor, Water Research, 3961 – 3971, vol. 42


manual & docs

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