Rapid Analysis of Eight Kinds of Catechins in Green Tea Beverage Using an Isocratic Elution Method by HPLC-UV on a Triacontyl Bonded Silica Gel Column

The main compound of green tea beverage behind astringency is a group of polyphenols called catechins. Catechins are considered to be a powerful antioxidant, and by protecting against gene mutation, it is also thought to slow down the aging process and prevent the formation of cancer cells. The rapid analysis of eight kinds of catechins {GC: (-)-gallocatechin; EGC: (-)-epigallocatechin; C: (+)-catechin; EC: (-)-epicatechin; EGCg: (-)-epigallocatechin gallate; GCg: (-)-gallocatechin gallate; ECg: (-)-epicatechin gallate; Cg: (-)-catechin gallate} in green tea beverage by high-performance liquid chromatography (HPLC) with an ultraviolet detector (UV) on a triacontyl bonded silica-gel column has been developed. In addition, a solution of acetonitrile - ethyl acetate - water (10 : 2 : 88, v/v) mixture containing 20mM phosphate was employed as the mobile phase for HPLC separation. This analytical method provides high linearity of the calibration curve as well as both repeatability and reproducibility. The correlation coefficient of the working curve of calibration were estimated to be from 0.9929 to 0.9997 for eight kinds of catechins in the concentration range from 10 mg L−1 to 100 mg L−1. The limits of detection (LOD) calculated on 3σ at 10 mg L−1 were 2.80 mg L−1 for GC, 1.82 mg L−1 for EGC, 0.70 mg L−1 for C, 2.80 mg L−1 for EC, 2.66 mg L−1 for EGCg, 1.81 mg L−1 for GCg, 1.16 mg L−1 for ECg, and 2.75 mg L−1 for Cg. The limits of quantification (LOQ) calculated on 10σ at 10 mg L−1 were 9.33 mg L−1 for GC, 6.07 mg L−1 for EGC, 2.32 mg L−1 for C, 9.34 mg L−1 for EC, 8.86 mg L−1 for EGCg, 6.05 mg L−1 for GCg, 3.88 mg L−1 for ECg, and 9.15 mg L−1 for Cg. Good results, the recoveries were from 87.9% to 99.2% and the relative standard deviations (RSD) were from 2.2% to 4.8%, were obtained in recovery tests by using green tea beverage. This proposed method could be successfully applied to the determination of eight kinds of catechins in green tea beverage.