Electronic tongue formed by sensors and biosensors containing phthalocyanines as electron mediators. Application to the analysis of red grapes

An electronic tongue formed by voltammetric sensors and biosensors containing phthalocyanines has been developed and used to analyze grapes of different varieties. The sensors are prepared using the carbon paste technique and have been chemically modified with different metallophthalocyanines. In turn, biosensors consist of carbon paste electrodes modified with phthalocyanines combined with tyrosinase or glucose oxidase. The response of the individual sensors towards model solutions of glucose and catechol have demonstrated that the voltammetric responses depend on the nature of the phthalocyanine, evidencing the important role of the electron mediator in the performance of the sensors. The capability of the system to discriminate grapes according to their sugar and their polyphenolic content has been evidenced using Principal Component Analysis. It has been demonstrated that the proposed array of sensors combines the advantages of classical phthalocyanine based sensors - that provide global information about the sample -, with the specificity of the enzyme substrate reaction typical of biosensors. For this reason, the selectivity of the multisensor system and its capability of discrimination is clearly improved when biosensors containing glucose oxidase or tyrosinase are included in the array.