Detection of sulfite via the trapping and subsequent electrochemical detection of hydrogen sulfide

The electrochemical oxidation of N,N-diethylphenylene-1,4-diamine (DEPD) and its subsequent reaction with sulfide has been exploited as a means of quantifying the latter. Re-oxidation of the resulting adduct was found to lead to an increase in the oxidative current which scaled linearly with sulfide concentration over the range 30 muM to 516 muM, although it was found that the upper limit could be extended through simply increasing the concentration of the DEPD indicator. As such the detection range is within an analytically relevant region with the detection limit of 4 muM comparing favourably with other electrochemical techniques. The approach has been extended to the detection of sulfite; this has been shown to be a facile yet robust process with complete recovery observed in the reductive conversion of sulfite to sulfide.