Multi-electrode detection in voltammetryPart 2.† Evaluation of a Hadamard multiplexed voltammetric technique

Abstract

A multiplex approach has been evaluated to obtain individual voltammetric signals coming from an array of independent microelectrodes. The multiplex design employs S matrices and the Hadamard transform to recover the signals for each electrode. Two pulse like voltammetric techniques, resembling the conventional normal pulse and differential pulse techniques, have been employed to generate the multiplexed currents. An array of 31 microelectrodes has been employed and the signal-to-noise ratio (S/N) obtained for the measurements presented a gain that is close to the 2.78 value predicted by the multiplex design. However, the reduction in the time interval spent for data acquisition was not 16, as predicted but 3 times. The increase in the data acquisition time for the multiplexed reading is a consequence of the pulse techniques employed. These techniques cause depletion of the electroactive specimen near the electrode surface. To overcome this problem a resting potential of 100 ms and a false multiplexed pre-scan must be employed. The gain in the S/N obtained allows for a three times enhancement in the detection limit for PbII determination when compared to the same non-multiplexed technique.