Multi-electrode detection in voltammetry - Part 3. Effects of array configuration Hadamard multiplexed voltammetric technique

The effect of the number of electrodes and their relative distribution on t he gain of the signal-to-noise ratio (SNR) in a multiplexed voltammetric me asurement was evaluated. A voltammetric multi-channel instrument was constr ucted capable of operating with up to 63 ultramicroelectrodes (mercury coat ed copper discs , diameter 55 mu m). The gain in the SNR was investigated a s a function of the number of electrodes (15, 31 and 63) in the array. For each array a design matrix was employed for the multiplexed measurements. T he results show that the detection limit for Pb(II) can be improved 5.1-fol d by employing 63 electrodes. The overlapping effect of diffusion layers wa s also evaluated and the results allow the conclusion that, for multiplexed readings obtained at 100 per second, and when the distance between adjacen t electrodes is less than 20 times their diameter, the radial component is disturbed, causing a reduction in the faradaic current. On the other hand, by keeping the distance greater than this limit, the multiplex gain can be fully achieved with a substantial reduction in data acquisition time.