Design of an electronic system and its application to electronic tongues using variable amplitude pulse voltammetry and impedance spectroscopy

Abstract

Electronic equipment (IDM-1) especially designed for the application of voltammetric and impedometric electronic tongues is described. For impedance spectroscopy the equipment permits the generation of sinusoidal signals with a frequency in the range of 1Hz to 1MHz and programmable amplitude up to 1 Vpp. For voltammetry the IDM-1 equipment generates a sequence of up to 32 pulses with an amplitude that can be configured for each of the pulses in the range [−0.5; +0.5V]. Voltammetric studies were performed using a total of eight working electrodes (i.e. Au, Pt, Ir, Rh, Ag, Cu, Ni, and Co) which were housed in a stainless steel cylinder used at the same time as both the body of the electronic tongue system and the counter/reference electrode. The width of the pulses can also be configured with a maximum value of 40ms. The system consists of a software application that runs on a PC and electronic equipment. In order to test the capabilities of the designed system, impedometric and voltammetric measurements were carried out on five different commercial cola drinks (brands I–V). Three different waveforms were used in the voltammetric study (i.e. staircase, ascendant SAPV and descendant SAPV). The voltammetric response and the impedance phase and module values obtained were processed using PCA. A remarkable discrimination between all cola drinks was seen using the descendant waveform and a group of metal electrodes (Ni, Co, Cu, Ag). In contrast, impedance spectroscopy technique discriminated one brand (brand I) from the others.