Determination of Organic Acids in Natural and Processed Foods by Isotacophoresis.

Abstract

A simple and rapid analytical method was developed by using isotachophoresis for simultaneous determination of organic acids including citric, tartaric, malic, fumaric, lactic, succinic, ascorbic, acetic, aspartic, glucuronic acids in fresh fruits and processed juices, and in carbonated and fermented drinks. The detection limits of this method are about 0.04 to 0.1 mg within the coefficient of variation of ca. 6%, and the entire analytical procedure can be accomplished within 30 min without any pretreatment of samples. Using this method, a leading electrolyte solution was prepared with 7 parts of 0.1% polyvinyl alcohol in 0.01 N HCl, buffered at pH 3.0 with β alanine, and 3 parts of methanol. A solution of 0.01 N n-caproic acid was used as the terminal electrolyte. There was a two stage migration procedure : the first stage in a 0.1 mm i.d. ×10 cm tube with 250 μA current for 10 min and the second stage in a 0.05 mm i.d. × 15 cm tube with 100 μA current for 10 min. The oven temperature was kept at 25°C. The nitrogen carrier gas was introduced at 0.25 Kg/cm2 pressure.