酸性络蓝K褪色光度法测定食盐中微量碘

PHOTOMETRIC DETERMINATION OF IODINE IN TABLE SALT BY A COLOUR FADING REACTION

在硫酸介质中 ,碘酸根对酸性络蓝 K具有褪色作用 ,且褪色的程度与碘酸根存在量有关 ,从而建立了光度法测定碘的新方法。方法最大吸收波长为 52 4 nm,表观摩尔吸光系数为 2 .1 9×1 0 4 L·mol-1·cm-1,碘的浓度在 0～ 60 μg/2 5ml范围内符合比耳定律。方法简单、快速、准确、选择性好、灵敏度高 ,用于测定碘食盐中的碘含量 。

It is found that in a H 2SO 4 medium, acid chrome blue K (abbreviated as ACBK) is oxidized by iodate, leading to the color fading of the dye. The fading of the color intensity of ACBK is found to be directly proportional to the amount of iodate present. Based on these facts, a photometric method for the determination of iodate in table salt is proposed. The decrease in absorbance (Δ A ) is measured at the wavelength of 524nm, which is the absorption maxima of ACBK, and the apparent molar absorptivity obtained at this wavelength is 2.19×10 4L·mol -1 ·cm -1 . Linear relationship between Δ A and the concentrations of iodate is found to be in the range of 0~60μg/25ml (as I 2).