Abstract: A new capillary electrophoretic method for the rapid and direct separation of seven organic acids in beverages was developed, with poly(1-vinyl-3-butylimidazolium bromide) as the reliable background electrolyte modifier to reverse the direction of anode electroosmotic flow (EOF) severely. Several factors that affected the separation efficiency were investigated in detail. The optimal running buffer consisted of 125 mmol/L sodium dihydrogen phosphate (pH 6.5) and 0.01 g/L poly(1-vinyl-3-butylimidazolium bromide). Highly efficient separation (105000 to 636000 plates/m) was achieved within 4 min and standard deviations of the migration times (n=3) were lower than 0.0213 min under optimal conditions. The limits of detection （S/N=3） ranged from 0.001 to 0.05 g/L. The present method was applied to determine a beverage sample (Mirinda) for sodium citrate, benzoic acid and sorbic acid with concentration of 2.64, 0.10 and 0.08 g/L, respectively. The recoveries of the three analytes in the sample were 100.3%, 100.7% and 131.7%, respectively. The method is simple, rapid, inexpensive, and can be applied to determine organic acids as additives in beverages.

Key words: anode electroosmotic flow, beverage, organic acids, polymeric ionic liquid, capillary electrophoresis (CE)