Simultaneous Determination of Pigments in Tea by Ultra-Performance Convergence Chromatography (UPC2)

Color is the most intuitive feature of different tea infusions. The accurate measurement of pigments is one of the important means for tea quality and bioactive appraisal. In this study, a stable, rapid, and environmental friendly method was developed for the simultaneous determination of seven pigments (alpha-carotene, beta-carotene, chlorophyll a, chlorophyll b, violaxanthin, lutein, and neoxanthin) by ultra-performance convergence chromatography coupled with photodiode array detector (UPC2-PDA). Carbon dioxide was employed as the primary mobile phase, instead of traditional organic solvents. The impacts of the chromatographic column, co-solvent, injection volume, pressure, and temperature on the separation of target pigments were evaluated systematically. Linear correlations were obtained (R-2>0.999). The accuracy of the method defined as the mean recovery was in the range from 70.1% to 101.2%. Assay precisions of the method at 0.5, 1.0, and 5.0 mu g g(-1) concentrations were all less than 4.8%. The proposed method was successfully used for the determination of the target pigments in tea with different degrees of fermentation.