A novel iTongue for Indian black tea discrimination

A novel impedance-Tongue (iTongue) based on multi-electrode Electrochemical Impedance Spectroscopy is proposed for discrimination of Indian black tea. Impedance response of platinum, gold, silver, glassy carbon, polyaniline and polypyrrole working electrodes in tea infusions for a sinusoidal excitation in the frequency range of 1 Hz to 100 kHz has been measured. Also, the percentage of major chemical constituents responsible for the tea quality has been determined by HPLC and UV–vis spectrophotometer. Frequency specific impedance response of these working electrodes along with the determined chemical concentrations was subjected to Principal Component Analysis to confirm the discriminability of the proposed iTongue. The correlations between the frequency specific impedance response of working electrodes and the chemical concentrations which depend on sample variability, such as harvest interval, manufacturing process and brand type have been established. These correlations were further used for dimensionality reduction and discriminability enhancement. The results show that the frequency specific responses of working electrodes play a key role in discrimination of Indian black tea which can be enhanced by combination of working electrodes and their frequency specific responses.