Multi-electrode detection in voltammetryPart I. A versatile multi-channel voltammetric instrument
A multi-channel voltammetric instrument is described for use with arrays of micro-electrodes. The instrument can access up to 31 electrodes in voltammetric measurements either independently or in groups (2–31 electrodes per group) and works in a simple two electrode like cell model, employing only one current-to-voltage converter. Two digital-to-analog converters were employed to ensure wide flexibility of the potential applied to the array. The control of the instrument, the data acquisition and treatment procedures were automated using an addressable asynchronous interface and a microcomputer running software written in QuickBasic 4.5. An array, containing 31 microelectrodes, embodied in a polyester isolating block, was constructed and employed for evaluation of the instrument performance. Each microelectrode was made of a sub-array containing seven copper discs (55 µm diameter) covered with a mercury film. Two new procedures to obtain voltammetric signals, at a scan rate equivalent to 3.2 V s–1, are proposed. These procedures access each electrode of the array while they are kept at different potentials, producing voltammetric pseudo-curves similar to those obtained by normal- and differential-pulse voltammetry. Other conventional voltammetric techniques such as potential staircase sweep, differential-pulse and anodic stripping voltammetry were also evaluated for use with the instrument, showing that the dynamic range of the measurements can be improved by selecting the number of electrodes to be employed without decreasing the scan rate.