流动注射分光光度法测定废水中砷

Flow injection spectrophotometric determination of arsenic in waste water

建立了测定砷（Ⅲ）的流动注射光度分析法。在0．5mol／L的硫酸介质中，溴酸钾的强氧化性将砷（Ⅲ）氧化成砷（Ⅴ），剩余的溴酸钾与碘化钾反应生成单质碘，利用碘与淀粉形成蓝色络合物，间接测定微量砷㈣。方法的线性范围为0．04～1．20μg／mL，检出限为6．2×10^-3μg／mL（3倍噪音）；除IO3，IO4，Cr2O7^2-等强氧化性阴离子外，其余阴离子以及大量常见阳离子对砷的测定没有干扰。对质量浓度为0．30gg／mL的As（Ⅲ）标准溶液连续进样11次测定，相对标准偏差为1．8％。该方法用于废水中砷的测定，加标回收率在98．7％～100．5％之间。

A new flow-injection spectrophotometric method has been developed for the determination of arsenic（Ⅲ）. After arsenic（Ⅲ）is oxidized to arsenic（Ⅴ）with strong oxidant like potassium bromate,the excessive potassium bromate in the system oxidizes continually potassium iodide to iodide,which forms a blue complex with starch. The complex can be used for determining arsenic indirectly in 0.5 mol/L sulfuric medium. The linear range for the determination is 0.04-1.20μg/mL,and the detection limit is 6.2 × 10^-3 μg/mL（3σ）. Other anions and large amounts of cations do not interfere in the determination of As（Ⅲ）except strong oxygenation properties of anions such as IO3^-,IO4^- and Cr2O7^2-. The relative standard deviation obtained is 1.8% for continual injection of 0.30 μg/mL As（Ⅲ）standard solution （n = 11）. The method has been applied to the determination of arsenic（Ⅲ）in waste water, and the relative standard deviation is between 98.7%-100.5%.