In recent years, electronic tongues have appeared as an excellent alternative to traditional analysis methods for product and process control in the food and agriculture industries. These systems combine electrochemical techniques such as potentiommetry or voltammetry with multivariate analysis tools in order to classify samples or quantify their physicochemical properties. Their main advantage in comparison with traditional methods is that they permit the implementation of fast, low-cost measurements avoiding the pre-processing of the samples and the need of qualified operators to carry out the analyses. Their operation is based on the use of cross-sensitive sensors, which permit the measurement of samples when there is interference between the different compounds.

In the present thesis an electronic tongue system based on voltammetry and impedance spectroscopy was developed. The designed system consists of a PC software application and Electronic Measurement Equipment able to carry out cyclic and pulse voltammetry measurements on up to 10 working electrodes. Impedance spectroscopy measurements in the range of frequencies from 1 Hz to 200 kHz can also be performed. The Electronic Measurement Equipment includes a potentiostat which enables the implementation of voltammetry and impedance spectroscopy tests in three electrodes mode. The software application permits configuration of the measurements, storage and pre-processing of the collected data and generation of the files needed to carry out the multivariate analysis.

The system has been electrically tested and excellent accuracy and precision levels for voltammetry and acceptable levels for impedance spectroscopy were obtained. Besides, validation tests were carried out for cyclic and pulse voltammetry. The results of these tests show that the designed system was able to reproduce the measurements carried out with commercial equipment (Autolab), and to classify different fruit juice samples. 

Finally, the voltammetric electronic tongue was applied in two experiments related to food and agriculture. Firstly, antioxidant solutions (ascorbic, citric and malic acids) were measured with seven noble and non-noble metal electrodes using cyclic and pulse voltammetry. Principal Components Analysis (PCA) and Partial Least Squares regression (PLS) were used to analyse the data and to generate the prediction models. The results obtained demonstrate that it is possible to precisely quantify the concentration of the three acids both in simple and binary solutions. It was also observed that the prediction models generated in electronic tongue configuration (combination of the seven electrodes) were as good as the models obtained with any of the individual electrodes.

In a second experiment, the ability of the system to detect glyphosate, a herbicide widely used in agriculture, was evaluated. Pulse voltammetry was applied to an electronic tongue made of eight metallic electrodes to measure solutions with different concentration levels of glyphosate, and the corresponding predictive models were generated with PLS. In this case, copper and cobalt electrodes showed better results than the combination of the eight electrodes. In order to improve the resolution of the measurements at low concentration levels, new tests were carried out with these two metals in a rotating disk electrode (RDE) configuration. The results obtained showed that the application of the pulse voltammetry to rotating disk electrodes allows the generation of robust and reliable prediction model for the quantification of glyphosate at concentration levels as low as 10-5M.

The ability of the voltammetric electronic tongue system to quantify different compounds in simple solutions and mixtures was demonstrated. In view of the good results, new experiments have been started with the objective of quantifying the physicochemical properties of foodstuffs and other complex matrices such as wastewater.