Kinetics and equilibria of tea infusion—Part 12. Equilibrium and kinetic study of mineral ion extraction from black Assam Bukial and green Chun Mee teas

The rates of infusion into distilled water of caffeine and of Cl−, H2PO4−, SO42−, C2O42−, K+ and Mg2+ ions have been measured at 80 °C, using both black orthodox Bukial and green Chun Mee tea leafs in the size range 1.70–2.00 mm. The analytical techniques employed were HPLC and ion chromatography. The total moles of positive charge extracted per litre of infusion were several times as large as the moles of negative charge of all the anions analysed, pointing to large concentrations of organic anions including polyphenolates. The kinetic data were fitted to first order plots. From the resultant rate constants the diffusion coefficients of the various species within the tea leafs were calculated and compared with the corresponding diffusion coefficients in pure water at 80 °C. The hindrance factors in the leafs were all of the order of 102.