Extraction and Ion Chromatographic Determination of Free and Combined Oxalic Acids in Vegetables

Abstract

Determinations of calcium oxalate in vegetables were carried out by extraction and ion chromatography of free and total oxalic acids. The free oxalic acid was extracted from the vegetables by immersion for 20min in boiling water. The total oxalic acid was extracted by immersion for one night in 0.1M HCl. The concentration of oxalic acid in the extracts was determined by ion chromatography. The amount of combined oxalic acid was calculated from the difference between the amount of the total oxalic acid and that of the free one; the content of calcium oxalate was also calculated. The contents of the free oxalic acid and calcium oxalate in several vegetables determined by the present method are presented.