Determination of Oxalic Acid in Vegetable Juices by Flow Injection Analysis using Roots of Barley Seedlings

Abstract

The concentration of oxalic acid in vegetable juices was determined in a flow injection system by using roots of barley seedlings as an immobilized oxalate oxidase reactor. In the pretreatment of the extracted vegetable juices, ascorbic acid was eliminated by the acetone powder of cucumber. Hydrogen peroxide produced from the decomposition of oxalic acid was reacted with the ABTS (2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) reagent and peroxidase. The oxidized ABTS was monitored spectrophotometrically at 405nm. The precision (coefficient of variation) was 3.1% at oxalic acid concentration of 0.2 mg/m/ level by 10 successive injections. The calibration curve of oxalic acid in this system gave the relative coefficient of 0.998. When this system was applied to some vegetable juices, the measured values agreed well with those obtained by the HPLC method.