H₂S Microsensor

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Detect H₂S in your sample

The H₂S microsensor is a reliable tool for studying H₂S production and oxidation in a wide range of applications. Tip size can be made as small as 10 µm for high spatial resolution of H₂S microprofiles. This combined with a fast response time of down to <10 seconds makes the H₂S microsensor a high-quality instrument for H₂S investigations.

The H₂S microsensor can be applied in a broad variety of research fields where non-destructive, fast and accurate measurements are required. The H₂S microsensor is designed for research applications within:

• Environmental sciences
• Biomedical sciences
• Biotechnology
• Microbiology
• Biogeochemistry

Microsensor technology:

Unisense offers two types of H₂S microsensors with different characteristics. Both types are miniaturized amperometric sensors with internal reference and a sensing anode. The anode is polarized against an internal reference. Driven by the external partial pressure, H₂S from the environment penetrates through the sensor tip membrane into the electrolyte where the H₂S is ultimately oxidised by the anode. This generates a current in the pA range which is measured by a high quality picoammeter e.g. the Unisense Microsensor Multimeter.

In the type I sensor (Sulf-xxx) the signal is generated by oxidation of H₂S directly on the anode in the tip of the sensor. The type I sensor is sensitive to hydrogen and should not be used in environments with high hydrogen concentrations. However, the type I sensor has a higher signal to noise ratio, has a longer warranty and expected lifetime than the type II sensor and is not sensitive to light.

The type II (H₂S-xxx) sensor is a customized sensor for samples containing H₂. In the type II sensor (H₂S-xxx) the H₂S, that enters through the membrane in the tip, is converted to HS- ions in the alkaline electrolyte. This is immediately oxidized 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 internal guard electrode facilitates a constant ratio of ferri- to ferrocyanide in the electrolyte, thus minimizing the zero-current. The ferri-/ferrocyanide complex is light sensitive and the sensors are painted black to minimize light interference.
Type II H₂S-xxx is made against a 10% customization fee compared to the equivalent SULF-xxx.

The type I sensor should be chosen in most environments because of higher signal to noise ratio and longer expected lifetime. If hydrogen is present in significant concentrations type II should be used.

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

Reference:

Jeroschewski, P., C. Steuckart, and M. Kühl. 1996. An amperometric microsensor for the determination of H2S in aquatic environments. Anal. Chem. 68: 4351–4357.

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