The Application of On-line Microdialysis with High Performance Liquid Chromatography for Determining Catechins in Tea and Tea Drinks

THOMAS CHING-CHERNG YANG* AND CHIA-CHEN CHANG

Department of Chemistry, National Kaohsiung Normal University, Kaohsiung 802, Taiwan (R.O.C.)

(Received: December 26, 2002; Accepted: March 25, 2003)

   A microdialysis on-line coupled to a reversed-phase liquid chromatography was investigated and applied for analyzing catechins in tea and tea drinks. Catechins in drink samples were diffused into the perfusate through a hollow fiber membrane and then on-line injected into the HPLC system. Catechins were separated with a C8 reversed column by gradient eluting using an acetonitrile/ phosphate buffer solution at pH 4.0, and monitored by a UV diode-array detector. Factors affecting the dialysis efficiency such as the conditions in perfusate and in the sample solution were evaluated. The proposed method provided a simple procedure for isolating catechins from tea and tea drink samples. The application was illustrated by the analysis of epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate in tea drinks.

Key words: HPLC, microdialysis, epicatechin, epicatechin gallate, epigallocatechin, epigallocatechin gallate, tea