High-Performance Liquid Chromatographic Determination of Free Sugars in Green Tea

Studies on the Free Sugars of Green Tea Part I

Abstract

A high-performance liquid chromatographic (HPLC) method for determining free sugars (glucose, fructose, sucrose, raffinose and stachyose) in green tea was investigated. A used column was Shodex Ionpak S-801, and a mobile phase was water. A refractive index detector was used for the detection of free sugars. Column temperature of 60°C and flow rate of the mobile phase of 0.5ml/min gave the best result for the separation of 5 free sugars, and xylitol was found to be the best compound for an internal standard. The preparation of free sugars from green tea was as follows; Four mg of xylitol was added to about 300mg of green tea, and its free sugars were extracted with 50ml of hot water for 15min in boiling water. The solution was passed through columns of Amberlite IRA-45 (15ml) ion exchange resin. The columns were washed with 100ml of water. The elute was concentrated to about 5ml and filtered through 0.45μm filter. This method will ensure the determination of free sugars in green tea with 1.80-11.51% of coefficients of varience and 99.2-102.1% of recovery.