Interpretation of Indian orthodox tea using multi-sensing impedometric technique.

Twelve different orthodox Indian tea samples were collected from tea growing and processing sites of Kangra (Valley), India. The percentage of major chemical constituents responsible for the tea quality has been determined by HPLC and UV-vis spectrophotometer. Impedance response using Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC), Polyaniline (PANI) (emraldine salt) and Poly Pyrrole (PPY) working electrodes in tea infusions in the frequency range of 1 Hz to 100 kHz has been measured for 30 days on each tea sample. The impedance response of these working electrodes along with the determined chemical concentrations was subjected to Principal Component Analysis (PCA). It was possible to map the antioxidant levels in these tea samples with few exceptions from the score plot of PCA.

Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.

In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes.