Electrochemically initiated 1,4-nucleophilic substitutions: A general strategy for the analytical detection of hydrogen sulfide

The reaction of electrochemically generated quinoid derivatives with sulfid e has been investigated as a method of detecting the latter. Five structura lly and functionally diverse precursor compounds (catechol, dopamine. hydro quinone. p-aminophenol and N,N-dimethylphenylene-1,4-diamine) were assessed as potential electrochemical indicators for aqueous sulfide. Each derivati ve is capable of forming a quinoid intermediate upon oxidation and all were found to respond to increasing concentrations of sulfide in pH 4 buffer (t ypically over a range extending from 10-300 muM sulfide). A number of strat egies for relating the observed electrochemical signal to the concentration of sulfide are presented. The relative merits of each system are discussed and their analytical parameters (linear range, detection limits, redo?: po tentials etc.) tabulated for ease of comparison.