MODELING THE TWIN PLATINUM PROBE SCANNING ELECTRODE RESPONSE

The signal response of a twin platinum probe scanning reference electr ode, when scanned across a localized electrochemical event, has been m athematically modeled. The model suggests that the key parameters that affect the signal response are the charge-transfer resistance (R-ct) and double-layer capacitance (C-dl) of the platinum electrodes, the in put impedance of the measuring device (R-m), and the scan time across the event. The phenomenon of ''signal shadowing,'' i.e., the appearanc e of cathodic artefacts following real anodes and vice verse, has prev iously been explained as a geometrical effect of the probe configurati on. Results presented as part of this work, however, suggest that the major contribution to shadowing is derived from the electrical respons e of the measurement circuit. Optimization of the equipment parameters indicates that a more accurate and precise representation of local el ectrochemical activity can be obtained by increasing the R-m/R-ct rati o and/or scan speed. Model predictions of the probe response correlate d well with real scans performed across a simulated localized event.