宽浓度范围水碘的碱性高锰酸钾氧化光度测定方法研究

Method for the determination of broad concentration range of iodide in drinking water by speetrophotometry with alkaline potassium permanganate oxidation

目的建立一种简单的光度比色法，测定饮用水中宽浓度范围碘化物。方法水中碘化物在碱性条件下经高锰酸钾氧化为碘酸盐，在酸性条件下用亚硝酸钠除去过量氧化剂并以氨基磺酸加尿素除去过量亚硝酸盐后，与碘化钾作用生成I2并与淀粉显色进行光度比色测定，测定体系中加适量本底微量碘及氯化钠，解决在水样含碘量〈100μg／L时碘-淀粉显色与水碘浓度不成线性比例的显色灵敏度问题。结果本方法标准曲线线性范围为0～1200μg／L（r=0．9998）；水碘检测限为4μg／L；对含碘量76．6、207．8、560．4μg／L水样各重复测定6次，相对标准偏差（RSD）均〈1％；8份不同含碘量水样加标回收率范围为97．0％（485．2／500．0）-102．5％（102．5／100．0）；试剂中加亚铁盐消除了水中6价铬（Cr^6＋）的干扰，加溴化钾及亚硝酸钠消除了水中溴酸盐（BrO3^-）的干扰，水中含0．2mg／L Cr^6＋、0．1mg／L BrO3^-不干扰测定。结论本方法操作简单，检测浓度范围宽，具有良好的精密度和准确度，适于应用。

Objective To establish a simple photometric method for the determination of broad concentration range of iodide in drinking water. Methods Iodide in water was oxidized with potassium permanganate in alkaline medium to generate iodate. After excessive oxidant was eliminated with nitrite sodium in acidic medium condition and excessive nitrite was eliminated with a mixture of aminosulfonic acid and urea, iodate was used to react with potassium iodide reagent to form I2 which further reacted with amylum to form color complex. The absorbance was determined by photometry. In determination reagent system suitable amount of iodide that acted as background and sodium chloride were added to solve the problem of the chromogenic sensitivity, i.e., when iodine concentration was 〈 100 μg/L in water sample the degree of iodine-starch complex color change could not be in linear proportion to the concentration of iodine in water. Results The linear range of the calibration curve of the new method for iodine was 0 - 1200 μg/L and the linear correlative coefficient was 0.9998. The delection limit for iodine was 4 μg/L. Results of 6 times repeated determination of water samples with iodine concentration of 76.6, 207.8, 560.4 μg/L showed that the relative standard deviations（RSD） were all under 1%. The recovery of standard addition for iodine added in 8 water samples of different iodide concentration levels was 97.0% （485.2/500.0） - 102.5% （102.5/100.0）. Interference of hexavalent chromium（Cr^6＋） in water was eliminated when treated with ferrous reagent. Interference of bromate （BrO3^-） in water was eliminated when treated with potassium bromide and nitrite sodium reagent. Zero point two mg/L Cr^6＋, 0.1 mg/L BrO3^- in water were noninterference. Conclusion This method can be easily performed with good precision and accuracy and has broad detection concentration range, which is suitable for measuring iodide in drinking water.