Simultaneous HPLC Determination of Gallic Acid,Catechins and Alkaloids in Tea

Using HPLC, an analytical method was developed to simultaneously determine the contents of gallic acid (GA) , 8catechins (i.e., GC, EGC, C, EGCG, EC, GCG, ECG and CG) and 3alkaloids (i.e., theobromine, theophylline and caffeine) in tea.Separation of the 12 chemicals on two chromatographic columns (Zorbax SB-C18 and TSKgel ODS-100Z) were investigated. The chromatographic conditions applied were the result from optimizations of the elution mode, pH of the mobile phase, column temperature and flow rate.They included:maintaining TSKgel ODS-100 Z column at 40℃, using 2‰ formic acid-water solution (mobile phase A) and methanol (mobile phase B) with the gradient elution mode of 83% A (0min) →75% A (5min) →73% A (7min) →58% A (16min) →83% A (18min) at the flow rate of 1.0mL·min-1, and detecting at the wavelength of 280 nm.Methodological evaluation and application on 6tea samples were subsequently conducted for verification.The correlation coefficients of the resulting linear equations for all of the components were greater than 0.9990, RSDs%of accuracy of the retention time and peak area lower than 0.105% and 4.076%, respectively, and the recovery rates from 97.767% to 104.766%.It appeared that the newly developed analytical method could yield linear relationships on data, as well as desirable precision, recovery and separability on the measurements for accurate and simultaneous determinations of gallic acid, catechins and alkaloids in tea.