Objective:Rapid determination of sulfur dioxide residues in Angelica dahurica. Methods:Chromogenic reaction of heat volatilization and phthalic two formaldehyde in hydrochloric acid medium ultraviolet visible spectrophotometric method. The sulfite in the sample is converted into sulfur dioxide by hydrochloric acid,heated and volatilized,diffused into the internal reaction tube, and reacts with o-phthalaldehyde and ammonium acetate solution to generate purple substance. Result:the product of purple reaction under the optimum conditions has strong UV-VIS absorption at 420nm wavelength,and the absorbance is proportional to the amount of sodium sulfite. A standard curve equation between absorbance and sulfite content was established. The linear correlation coeffi-cient of the equation was 0. 9935,and the linear relationship was good. Conclusion:This method is simple,rapid,less reagent and can provide reference for the determination of sulfur dioxide residue in Angelica dahurica.%采用盐酸介质中热挥发扩散-邻苯二甲醛显色反应-紫外-可见分光光度法测定白芷中二氧化硫残留量.样品中的亚硫酸盐被盐酸转化为二氧化硫,受热挥发,扩散至内反应管,与邻苯二甲醛、乙酸铵溶液反应生成的紫色物质.最佳测定条件下的紫色反应产物在420nm波长下具有较强的紫外-可见吸收,且吸光度与亚硫酸钠加入量成正比.据此建立吸光度与亚硫酸盐含量的标准曲线方程,方程线性相关系数r为0.9935,线性关系较好.该法简便、快速、试剂用量少、不受样品基质干扰,可为白芷二氧化硫残留量的测定提供参考.
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