Abstract:

The effects of temperature and amount of added HCl 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 watersoluble oxalate was extracted using water at different temperatures, and total oxalate was extracted using different amounts of 0.5 mol/L HCl solution. The centrifugation supernatant of extracts were supernatant 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 HCl 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.

Key words: vegetable, oxalate, extraction, ion chromatography