蔬菜中不同形态草酸的提取测定

Extraction and Determination of Different Forms of Oxalate in Vegetables

采用离子色谱法研究不同温度和盐酸加入量对菠菜、苋菜、芫荽、韭菜4种蔬菜水溶性草酸和总草酸提取测定的影响。水溶性草酸用不同温度的水溶液提取,总草酸用不同量的0.5mol/LHCl浸提,离心稀释过滤后上机测定。菠菜和苋菜的水溶性草酸随提取温度的升高而增大,总草酸含量在0.5～2ml0.5mol/LHCl范围内随盐酸加入量的增加而增大;而芫荽和韭菜的水溶性草酸和总草酸含量随提取温度和盐酸加入量的变化不大。采用2ml0.5mol/LHCl浸提总草酸,用沸水浴20min浸提水溶性草酸,适用于不同类型蔬菜样品草酸的提取测定。4种蔬菜中草酸的加标回收率在95.5%～103.5%之间,水溶性草酸和总草酸含量顺序均为菠菜>苋菜>韭菜>芫荽。该方法具有操作简便、干扰小、灵敏、回收率高等特点,适用于蔬菜不同形态草酸的提取测定。

The effects of temperature and amount of added HC1 on the extraction of water-soluble oxalate and total oxalate from four vegetables （spinach, amaranth, coriander and Chinese chive） were investigated by ion chromatographic method. The water- soluble oxalate was extracted using water at different temperatures, and total oxalate was extracted using different amounts of 0.5 mol/L HC1 solution. The centrifugation supernatant of extracts were supematant diluted and filtrated well enough prior to ion chromatographic detection of oxalate. The water-soluble oxalate contents of spinach and amaranth increased with the increase of temperature, and their total oxalate contents increased with the increase of addition amount of 0.5 mol/L HCl in the range of 0.5 -- 2 ml. While no significant changes in both the two forms of oxalate in Chinese chive and coriander were found when temperature and HC1 addition amount were changed. The best extraction efficiency was obtained when total and water-soluble oxalates were extracted using 2 ml of 0.5 mol/L HCl and boiled water for 20 min respectively. The recoveries of water-soluble and total oxalate in the four vegetables were between 95.5 % and 103.5 %, and the contents of total and water-soluble oxalates both decreased in the following order： spinach 〉 amaranth 〉 Chinese chive 〉 coriander. This method is easy to operate, with little interference as well as high sensitivity and recovery and therefore is applicable to the determination of different forms of oxalate in various vegetables.