在1.0 mol·L-1乙酸介质中,银(Ⅰ)对过硫酸钾氧化罗丹明B的褪色反应具有强的催化作用,砷(Ⅴ)对上述指示反应具有灵敏的阻抑作用,从而建立了一种阻抑动力学光度法测定砷的方法.对酸介质的种类和酸度、试剂用量、反应温度、反应时间、稳定时间和共存离子的干扰等进行了试验并予以优化.试验结果表明:在554 nm最大吸收波长处,砷(Ⅴ)的质量浓度在80 μg·L-1以内,lg(A0/A)与砷的质量浓度呈线性关系,检出限(3S/N)为1.23×10-6g·L-1.方法用于环境水中痕量砷(Ⅴ)的测定,测得方法的回收率在95.5%~102.8%之间,测定值的相对标准偏差(n=9)在0.9%~3.9%之间.

It was found that in 1.0 mol·L-1 acetic aicd medium,the redox reaticon between rhodamine B and potassium persulfate was strongly catalyzed by Ag(Ⅰ) ion,leading to an enhancement of fading of color of the rhodamine B.This indicator reaction was inhibited by the presence of As(Ⅴ) ion. Influential factors,including the kinds and concentration of acid medium,amount of reagent,temperature and time of reaction,time of stability,and interferences of coexisting ions were studied.Linear relationship between values of lg(A0/A)and concentration of As(Ⅴ) ion was obtained within 80 μg·L-1 when measured at the absorption maximum of 554 nm.Detection limit (3S/N) of the method found was 1.23×10-6g·L-1.The proposed method was used in the determination of As(Ⅴ) ion in environmental water sample,giving values of recovery ranged from 95.5% to 102.8%,and values of RSD′s (n=9) in the range of 0.9%~3.9%.