Hydrogen sulfide (H<sub>2</sub>S) is an endogenously-produced, gaseous signaling molecule with integral functions in the neurological, cardiovascular, gastrointestinal, and endocrine systems. The use of hydrogen sulfide as a therapeutic has been hindered by dispute over what concentrations are physiologically relevant or required. Real-time, continuous sensing is currently restricted to indirect, redox mediator-based electrochemical methods as direct oxidation of hydrogen sulfide produces insoluble elemental sulfur that rapidly passivates the working electrode surface. To investigate the possibility of electrochemically regenerating the electrode, the impact of the applied potential on the rate of passivation and elemental composition of the sulfur layer were studied on a glassy carbon electrode. Increasing anodic potential showed a drastic decrease in the amount of passivating sulfur, that may be attributed to electrooxidation of adsorbed sulfur to water-soluble sulfate ions. To exploit this favorable phenomenon, the use of triple pulse amperometry (TPA) was investigated, where by surface regeneration and measurement pulses cycled continuously for real-time sensing. In this manner, hydrogen sulfide was oxidized directly without undesirable sulfur passivation. Sensors operated under TPA retained similar sensitivity, response time, and detection limit for six consecutive calibration cycles. In contrast, the use of constant potential amperometry resulted in significant sensitivity drift that negatively impacted the linear range and accuracy of the sensor. The calibration linear dynamic range achieved with TPA covered the most commonly reported biological concentrations of 1-100 µM with adequate sensitivity (&gt;20 nA/µM). This self-regenerating approach should enable improved monitoring of hydrogen sulfide concentrations related to therapeutics and other biological outputs.

Direct electrochemical sensing of hydrogen sulfide

253rd National Meeting (2017)

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