用维多利亚蓝BO作显色剂光度法测定微量碘

PHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF IODIDE WITH VICTORIA BLUE BO

在盐酸溶液中，且在溴水的存在下，试样溶液中的碘化物离子转化为IO3^-，加入甲酸钠溶液除去多余的溴后加入过量碘化物（以KI形式加入）使与IO3^-反应释出I2且与过量I^-离子络合形成I3^-。在pH2左右的磷酸-磷酸二氢钠缓冲溶液中并在非离子表面活性剂OP存在下，I3^-络阴离子与维多利亚蓝BO（VB-BO）反应生成呈艳蓝色的离子缔舍物，吸收峰在580nm波长处。表观摩尔吸光系数为1．84×10^5L·mol^-1·cm^-1碘化物浓度在0～0．5mg·L^-1范围内遵守比耳定律。应用此法测定食盐中微量碘，试验结果的RSD均小于2％，回收率在98．7%至100．6%之间。

In a hydrochloric acid medium, and in the presence of bromine water, iodide in the sample solution was transformed into IO3^-. After removal of excess bromine by adding sodium formate solution, more iodide （in form of KI） was added to react with IO3^- to liberate iodine which was complexed with excess iodide to form I3^-. In a NaH2PO4-H3PO4 buffer medium of pH around 2, and in the presence of non-ionic surfactant OP, an association complex between I3^- and victoria blue BO （VB-BO） was formed which showed a gorgeous blue color. The absorption of the colored complex was measured at its absorption maxima of 580 nm, where the apparent molar absorptivity was found to be 1.84×10^5L·mol^-1·cm^-1. Beer＇s law was obeyed in the range of 0 to 0. 5 mg · L^-1 of iodide. The proposed method has been applied to the analysis of table salt samples, giving RSD＇ s less than 2%, and recoveries in the range from 98. 7% to 100. 6%.