Collect. Czech. Chem. Commun. 1991, 56, 192-205

Rapid scanning voltammetry under steady-state conditions in a flow through thin layer cell with a microelectrode

Russel J. Taita, Alan M. Bonda, Barrie C. Finninb and Barry L. Reedb

a Department of Chemical and Analytical Sciences, Deakin University, Geelong, Victoria, 3217, Australia
b School of Pharmaceutics, Victorian College of Pharmacy, 381 Royal Pde, Parkville, Victoria, 3052, Australia


A microelectrode based detector system has been developed for measurement of steady state voltammetric curves in flowing solutions. Two microprocessors operating in parallel allow the direct transfer of collected data to a floppy diskette. Long term experiments can then be performed, with individual voltammograms being rapidly obtained, recorded and stored. The system can be used with scan rates up to 10 V s-1 and with 1 mV resolution over a potential range of 2.5 V. When a 10 μm diameter micro-disk platinum electrode serves as the working electrode, rapid scan voltammetry (scan rate 1 to 10 V s-1) can be undertaken under steady state conditions for reversible processes with a flow rate in the range of 1 to 3 ml min-1 as evidenced by the observation of sigmoidal rather than the peak shaped curves obtained with previously described rapid scan systems. That is, complete voltammograms can be obtained with minimal distortion due to uncompensated resistance and charging current which is not the case when conventionally sized electrodes are used or when microelectrodes are used at excessively high scan rates where linear diffusion terms become important. The working microelectrodes were developed to suit a conventional thin-layer cell design and therefore permit ready adaptation to existing flow through electrochemical detection systems. The detection limits for the determination of ferrocene in methanol at flow rates up to 3 ml min-1 were 10-6 mol dm-3 after background correction, and the response was found to be linear over the concentration range 10-3 to 10-6 mol dm-3. Three-dimensional methods of data treatment and contour plots can be used to interpret results obtained from steady state or near steady state voltammograms of incompletely resolved chromatograms as demonstrated with range of biologically important compounds.