A Rapid Dialysis Method for Analysis of Stevioside and Rebaudioside A in Foods

A rapid dialysis method for the analysis of stevioside (SS) and rebaudioside A (RS) in foods was developed. Minced samples (10 g) were packed into 30 cm net length dialysis tubing with 30% methanol to increase the dialysis efficiency. The dialysis tubing was put in a 100 mL centrifuge tube, and the total fluid volume was made up to 100 mL with 30% methanol. Dialysis was done with shaking while heating at 50℃. The dialysis times were reduced from 48-72 hr in the conventional method to 2 hr under these conditions. The dialysate was loaded on a C18 solid- phase extraction cartridge, and the cartridge was washed with 40% methanol. SS and RS were eluted from the cartridge with 80% methanol, and separated by reversed-phase HPLC. Recovery yields (%)of SS and RS, spiked at 0.02 g/kg in various foods, were 83.0-105.1% and the relative standard deviations were mostly less than 5%.