Determination of Caffeic Acid and Gallic Acid in Tea Samples by Capillary Electrophoresis with Bi-directional Electrostacking

A bi-directional electrostacking combining with capillary electrophoresis method was proposed to analyze organic acid ions in tea samples.Salt bridges were replaced by porous cores to separate running buffer and electrode solution,and the bi-directional electrostacking setup was improved to be integrative.The analytical procedure was controlled by a computer.The experimental parameters,including electrostacking time,applied voltage and sample volume,etc.were investigated.Under the optimal condition,the enrichment factors of caffeic acid and gallic acid were 24 and 20,respectively.The limits of detection were 0.4 mg/L and 0.2 mg/L,respectively.The calibration curves were linear in the range of 1.2-800 mg/L for caffeic acid and 0.8-800 mg/L for gallic acid.The method was used in the determination of caffeic acid and gallic acid in tea samples with recoveries of 99%-109%.