| Abstract
| - The voltammetric response of a 10% (by weight) N,N‘-diphenyl-p-phenylenediamine (DPPD) and 90% (by weight)carbon and binder screen-printed electrode has beenexamined in aqueous media over a range of pH usingcyclic voltammetry both in the presence and in theabsence of sulfide. In the absence, the screen-printedelectrode undergoes an initial oxidative process on thesurface of the solid organic particles to form an insolublelayer of the corresponding cation radical salt, DPPD•+X-,where X- is an anion present in the solution. The chargetransfer is thought to occur at the three-phase boundarybetween solid DPPD, carbon, and the aqueous solution.At higher potentials, a second oxidative wave is observedthat is attributed to the oxidation of the bulk DPPD withintercalation of the anion species present to form a solidphase of DPPD•+X-. The two voltammetric processes werefound to stabilize after repetitive scanning, after whichtime, sulfide was added to the solution. The voltammetricresponse was found to respond to sulfide by showing adecrease in both the oxidative and reductive waves, whichcan be attributed to the sulfide effectively blocking thethree-phase boundary. The response was found to beindependent of the electrode used and at pH 4 produceda linear range from 20 to 165 μM, and a limit of detectionof 7.5 μM for sulfide detection was achieved.
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