Stephen Nigel Davies

Electrochemical detection of sulphide: a novel dual flow cell

Abstract A novel application of a dual flow electrochemical cell to the detection of hydrogen sulphide is presented. The sensor employs the electrochemically initiated reaction of N , N- dimethylphenylene-1,4-diamine (DMPD) with sulphide as the main analytical signal. The redox indicator is passed through one channel while sulphide effluent is flowed through the other with the streams separated by the use of a gas-permeable membrane. Preliminary results have shown that the sensor responds linearly to sulphide over the range 20–103 μM with the signal profile and response time capable of modulation through variation in the flow rates of the two streams.

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

The reaction of electrochemically generated quinoid derivatives with sulfide has been investigated as a method of detecting the latter. Five structurally and functionally diverse precursor compounds (catechol, dopamine. hydroquinone. p-aminophenol and N,N-dimethylphenylene-1,4-diamine) were assessed as potential electrochemical indicators for aqueous sulfide. Each derivative is capable of forming a quinoid intermediate upon oxidation and all were found to respond to increasing concentrations of sulfide in pH 4 buffer (typically over a range extending from 10-300 muM sulfide). A number of strategies 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?: potentials etc.) tabulated for ease of comparison.

Electrochemically Initiated Reactions of Diphenylamineswith Sulfide: Application to the Voltammetric Detectionof Hydrogen Sulfide

The electrochemical behavior of three diphenylamine derivatives in the presence of sulfide and sulfhydryl thiols (RSH) in aqueous solution on a glassy carbon electrode has been investigated. All three are shown to exhibit modified voltammetric profiles upon the addition of low concentrations of sulfide, which may provide alternative routes for the detection of this important analyte. The various strategies within which they can be employed have been identified and a brief comparison of their analytical utility (limit of detection, linear range, selectivity etc.) compiled. The reaction of sulfide with 4,4-diaminodiphenylamine is shown to be particularly promising with a number of options through which sulfide levels could be identified. Evidence for the electrochemical formation of the sulfur heterocycle, thionine, is presented and the potential advantages of such reactions highlighted.