Ohkawa H
J Assoc Off Anal Chem. 1985 Jan-Feb;68(1):108-11.
A new quantitative gas chromatographic (GC) method has been developed for the determination of oxalic acid in foods. Solid sample is extracted with water (soluble oxalic acid) or 2N hydrochloric acid (total oxalic acid) at room temperature. An aliquot of sample extract is evaporated to dryness, and the oxalic acid in the residue is methylated with 7% hydrochloric acid-methanol. The reaction mixture is extracted with chloroform, and dimethyl oxalate is quantitated by GC. Recovery of oxalic acid added to liquid samples averaged 100.6%; recoveries from extracts of solid samples were 96.2-99.5 and 97.2-100.1% for water and hydrochloric acid extractions, respectively. Results are shown for determination of oxalic acid in spinach and beverages. The technique is simple, rapid, and accurate, and small samples may be used. The limit of determination is 20 micrograms.
已开发出一种新的定量气相色谱（GC）方法用于测定食品中的草酸。固体样品在室温下用水（可溶性草酸）或2N盐酸（总草酸）进行提取。取一份样品提取物蒸发至干，残留物中的草酸用7%盐酸-甲醇进行甲基化。反应混合物用氯仿萃取，草酸二甲酯通过气相色谱进行定量。添加到液体样品中的草酸回收率平均为100.6%；固体样品提取物用水和盐酸提取时的回收率分别为96.2 - 99.5%和97.2 - 100.1%。给出了菠菜和饮料中草酸测定的结果。该技术简单、快速且准确，可使用少量样品。测定限为20微克。
