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

Abstract

The effect of the number of electrodes and their relative distribution on the gain of the signal-to-noise ratio (SNR) in a multiplexed voltammetric measurement was evaluated. A voltammetric multi-channel instrument was constructed capable of operating with up to 63 ultramicroelectrodes (mercury coated copper discs , diameter 55 µm). The gain in the SNR was investigated as 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. The results show that the detection limit for Pb(II) can be improved 5.1-fold by employing 63 electrodes. The overlapping effect of diffusion layers was also evaluated and the results allow the conclusion that, for multiplexed readings obtained at 100 per second, and when the distance between adjacent 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.