| Popis: |
Anodic voltammetric detection of sulfhydryl compounds, represented here by cysteine, at Pt electrodes in acidic media occurs concomitantly with anodic generation of surface oxide. It is speculated that the adsorbed hydroxyl species (PtOH), proposed to be the intermediate product in formation of the inert oxide (PtO), is the source of O-atoms transferred to the stilfonic acid produced by oxidation of the sulfhydryl moiety. However, as a consequence of this electrocatalytic response mechanism, application of the traditional three-step waveform for pulsed amperometric detection (PAD) of sulfhydryl compounds is accompanied by a large background signal resulting from PtO formation. To diminish the background signal, the traditional three-step PAD waveform has been modified by insertion of a brief (100 ms) anodization step prior to the detection step to activate the Pt surface by generation of PtOH with minimal conversion to PtO. The subsequent negative step from the activation potential to the detection potential {Eoet < permits the PtOH to be harvested in the detection |
