COMPARISON OF DIRECT-CURRENT, DERIVATIVE DIRECT-CURRENT, PULSE AND SQUARE-WAVE VOLTAMMETRY AT SINGLE DISC, ASSEMBLY AND COMPOSITE CARBON ELECTRODES - STRIPPING VOLTAMMETRY AT THIN-FILM MERCURY MICROELECTRODES WITH FIELD-BASED INSTRUMENTATION

A comparative investigation of normal and stripping forms of voltammet ry was undertaken at single and random array microdisc, macrodisc and composite carbon electrodes using dc, derivative dc, square-wave and d ifferential-pulse waveforms, Studies on the reduction of [Fe(CN)(6)](3 -) in 0.05 M KNO3 revealed that the dc waveform with derivative readou t is superior to the use of square-wave or differential-pulse waveform s at both single disc and random array carbon fibre electrodes, Analyt ical superiority to that obtained at a conventional glassy carbon macr odisc electrode was also observed. The detection limit for the determi nation of [Fe(CN)(6)](3-) was 4 x 10(-6) M at the carbon fibre random array microdisc electrode and 6 x 10(-6) M when using a single disc mi croelectrode (scan rate = 200 mV s(-1)), For the determination of Pb a nd Cd in 0.1 M HCl by stripping voltammetry, the ideal combination of high sensitivity (greater than or equal to 1 ppb detection limit), avo idance of the need to remove oxygen or utilise solution stirring or el ectrode rotation could be achieved at mercury-plated thin film single disc or random array microelectrodes or composite electrodes. Furtherm ore, under these thin film conditions, the analytical performance of e ach of these three electrode types improved with respect to signal-to- background current ratio as the scan rate increased. Consequently, sho rt potential scanning times as well as optimum sensitivity are achieve d with scan rates in the 1-50 V s(-1) range. All of the results obtain ed demonstrate that highly sensitive field-based voltammetric analysis may be accomplished using the combination of an inherently simple two -electrode battery operated instrument, the de waveform and random arr ay or single carbon fibre microdisc working electrodes, An interface w hich enables voltammetric studies to be undertaken with a battery oper ated personal computer is described for this purpose.