Voltammetric e-tongue for the quantification of total polyphenol content in olive oils

This work presents the application of a voltammetric electronic tongue made from an array of polypyrrole modified screen printed electrodes in the qualitative and quantitative analysis of phenolic compounds found in virgin olive oils. Virgin olive oil samples in the form of emulsions were analyzed by sensors using cyclic voltammetry. The cyclic voltammograms show peaks related to redox processes related to polypyrrole and phenolic compounds presents in the emulsions. The obtained responses were pre-processed employing kernel method in order to extract significant information from the voltammetric signals. These coefficients were used as matrix input in multivariate data analysis. Additionally, the kernel coefficients were used in multivariate calibration method by partial least squares, which accomplished the quantification of total polyphenol content. Training and test sample results were compared with the ones obtained with the spectrophotometric method. High significant correlation coefficient of 0.9976 and 0.9884 was accomplished in calibration and prediction, in the range from 111.75 to 482.42 mg x kg(-1). Qualitative discrimination of different phenolic compounds found in olive oils was also evaluated by principal component analysis and partial least squares discriminant analysis when these are added in olive oil emulsions. (C) 2013 Elsevier Ltd. All rights reserved.