Emerging analytical tools for the detection of the third gasotransmitter H₂S, a comprehensive review

Hydrogen sulfide (H₂S) is currently considered among the endogenously produced gaseous molecules that exert various signaling effects in mammalian species. It is the third physiological gasotransmitter discovered so far after NO and CO. H₂S was originally ranked among the toxic gases at elevated levels to humans. Currently, it is well-known that, in the cardiovascular system, H₂S exerts several cardioprotective effects including vasodilation, antioxidant regulation, inhibition of inflammation, and activation of anti-apoptosis. With an increasing interest in monitoring H₂S, the development of analysis methods should now follow.

This review stages special emphasis on the several analytical technologies used for its determination including spectroscopic, chromatographic, and electrochemical methods. Advantages and limitations with regards to the application of each technique are highlighted with special emphasis on its employment for H₂S in vivo measurement i.e., biofluids, tissues.

Fluorescence methods applied for H₂S measurement offer an attractive non-invasive and promising approach in addition to its selectivity, however they cannot be considered as H2S-specific probes. On the other hand, colorimetric assays are among the most common methods used for in vitro H₂S detection, albeit their employment in vivo H₂S measurement has not yet been possible . Separation techniques such as gas or liquid chromatography offer higher selectivity compared to direct spectrophotometric or fluorescence methods especially for suitable for endpoint H₂S measurements i.e. plasma or tissue samples. Despite all the developed analytical procedures used for H₂S determination, the need for highly selective, much work should be devoted to resolve all the pitfalls of the current methods.