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本文探讨了碘与淀粉的相互作用以及碘－淀粉显色体系的稳定性。结果表明：在碘量一定时，体系的吸光度随淀粉用量的增大而增大，最后趋向稳定；在淀粉量一定时，体系的吸光度随碘用量的增大而增大，最后亦趋向稳定。碘－淀粉显色体系很不稳定，吸光度随时间呈比较明显的下降趋势，但加入复合表面活性剂可以使显色体系的稳定性大大提高。在上述结果的基础上，我们建立了测定Ｖｃ的新方法，此法具有简单、快捷、试剂易得、灵敏度高以及对浑浊试液不必分离即可直接测定等优点。该法的灵敏度为０．２５μｇ／ｍｌ，对１μｇ／ｍｌ的Ｖｃ试液进行平行测定，１０次平行测定结果的相对标准偏差为８．８６％，加标回收率为９０．５％－９３．６％，用于番石榴汁饮料中Ｖｃ的测定，结果满意。
This article explores the interaction of iodine with starch and the stability of iodine-starch chromogenic systems. The results showed that when the iodine amount was constant, the absorbance of the system increased with the increase of the amount of starch and finally stabilized. When the amount of starch was constant, the absorbance of the system increased with the increase of the amount of iodine and finally stabilized. The iodine-starch color system is unstable, and the absorbance decreases obviously with time, but the addition of complex surfactants can greatly improve the stability of the color system. Based on the above results, we established a new method for the determination of Vc. This method has the advantages of simple, fast, easy reagent acquisition, high sensitivity and direct determination of turbid solution without separation. The sensitivity of the method was 0.25μg / ml. The relative standard deviation of the 10μg parallel assay was 8.86% with the recovery of 90.5% -93. 6% for the determination of Vc in guava juice beverage with satisfactory results.