Analytical Sciences

Abstract − Analytical Sciences, 16(2), 139 (2000).

Enhanced Separation and Elution of Catechins in HPLC UsingMixed-Solvents of Water, Acetonitrile and Ethyl Acetateas the Mobile Phase
Midori KUMAMOTO,* Tamiyoshi SONDA,* Kazumi TAKEDOMI,* and Masaaki TABATA**
*Department of Food and Nutrition, Faculty of Home Science, Nishikyushu University, Kanzaki-machi, Saga 842-8585, Japan
**Department of Chemistry, Faculty of Science and Engineering, Saga University,1 Honjo-machi, Saga 840-8502, Japan
We conducted a study for the separation of four catechins ((-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechingallate (ECG) and (-)-epigallocatechin gallate (EGCG)) in tea by HPLC with an electrochemical detector atdifferent temperatures (25 - 50กร). Various solvent compositions of mixed solvents of water, acetonitrile (AN) and ethylacetate (EA) were used as eluting solvents. The compositions of the solvents were as follows: water, 90 - 70% (v/v); AN,10 - 30% (v/v); EA, 0 - 5% (v/v). The binary mixtures of water (90 - 70% (v/v)) and AN (10 - 30% (v/v)) were not ableto separate the peaks of EC and EGCG under all of the different solvent compositions. However, ternary mixed-solventscontaining a small amount of EA (3 - 5% (v/v)) with water (85 - 83% (v/v)) and AN (12% (v/v)) separated four catechinssufficiently, especially the peaks of EC and EGCG, within a 10 min elution time at 40กร. The effect of the solventcomposition is discussed in terms of the ET N and DII,I values, solvent structure and extraction constants of catechins intoEA. The formation of a pseudo stationary phase in which ODS is partly covered by EA is proposed for the enhancedseparation of EC and EGCG in the presence of EA. Catechins in three kinds of tea were determined under an optimumcondition.