Using various metal phthalocyanine mixed with graphite for selective electrodes of electronic tongue to classify several types of hot drink

Abstract

Metal phthalocyanine (MPc) is a metal organic compound which can be formed with several metal atoms at the center. Although MPc has semiconductor property, in order to fabricate the selective electrode for cyclic voltammetry (CV) measurement, the other material with high electrical conductive materials is required to mix in order to achieve sufficient electrochemical current. In this work, graphite powder with particle size less than 20 μm from Sigma-Aldrich Pte. Ltd. was mixed with several MPc powders including cobalt, iron, zinc and manganese phthalocyanine powders in the ratio of 20:1 by weight, respectively. The mixture powder was grinded together to achieve the uniform mixing with some powder size. In order to fabricate the selective working electrodes, the mixture was fill into a hollow Teflon rod with inner copper rod at the other end. During CV measurement, the electrodes indicated the anodic and cathodic peaks at various voltage depending on the type of metal atom of MPc therefore these modified graphite electrodes are suitable to be utilized as a selective probe for electronic tongue system. To demonstrate the classification ability of this electrode array, a variety of hot drink was used including three types of coffee, cocoa and chocolate malt. The hot drink was prepared with boil water and cooled it down to 30 °C before performing the CV measurement by five electrodes. With principle analysis, the extracted feature can separate each data group of five hot drinks and even can distinguish three types of the coffee. Thus, these graphite modified electrodes can be utilized in an electronic tongue application with low cost and high stability.