A direct and selective electrochemical hydrogen sulfide sensor

Highlights: • Amperometric measurement of hydrogen sulfide (H₂S) is challenging due to electrode poisoning with solid sulfur byproduct. • Concomitant electrode passivation reduces H₂S sensitivity and results in performance variability with use. • Surface conditioning procedure on a glassy carbon electrode (GCE) evades passivation-related performance variability. • Use of electropolymerized film improves electrode's selectively for H₂S and performance in biological media. -- Abstract: Continuous, in situ detection of hydrogen sulfide (H₂S) in biological milieu is made possible with electrochemical methods, but direct amperometry is constrained by the generation of elemental sulfur as an oxidative byproduct. Deposition of a sulfur layer passivates the working electrode, reducing sensitivity and causing performance variability. Herein, we report on the use of a surface preconditioning procedure to deposit elemental sulfur on a glassy carbon electrode prior to measurement and evaluate performance with common analytical metrics. The lack of traditional anti-poisoning techniques (e.g. redox mediators, cleaning pulses) also allowed for facile surface modification with electropolymerized films. For the first time, a series of electropolymerized films were characterized for their H₂S permselective behavior against common biological interferents. Highly selective, film-modified electrodes were then evaluated for their anti-biofouling ability in simulated wound fluid. The final optimized electrode was capable of measuring H₂S with a low detection limit (i.e., <100 nM) and ∼80% of its initial sensitivity in proteinaceous media.