碘-罗丹明B-OP体系分光光度法测定水中溶解氧

Spectrophotometric determination of dissolved oxygen in water through iodine-rhodamine B-OP system

基于I3^-与罗丹明B在OP存在下结合成电中性的离子缔合物在360nm波长处有最大吸收，提出了水样中溶解氧的光度法测定。于待测水样中加入硫酸锰及碱性碘化钾溶液，水中溶解氧与之形成Mn3O3沉淀，加入浓硫酸使与Mn2O3沉淀反应而析出单质碘，在酸性条件下析出的碘与罗丹明B溶液在360nm波长处有最大吸收，以碘酸钾为基准物，时水样中溶解氧含量进行分光光度法测定。溶解氧浓度在0．0027～0．686mg／L范围内符合比尔定律，表观摩尔吸光系数为4．012×10^4L·cm^-1·mol^-1，方法的捡出限为0．0010mg／L。此法对不同来源的水样中溶解氧含量进行测定，所得结果与碘量法及溶解氧测定仪所测得的结果相符合。

Based on the reaction between iodine and rhodamine B which produced a ion-association complex with its absorption maximum at the wavelength of 360 nm, a photometric determination of dissolved oxygen in water was proposed. Dissolved oxygen in the sample was precipitated by adding MnSO4 in an alkaline medium to form Mn2O3 from which oxygen was liberated upon addition of H2SO4, and reacted with the free I2 liberated by the reaction of KI with H2SO4. The absorbance of ion-association complex was measured photometrically at 360 nm. The content of dissolved oxygen was found from the standard curve drawn by using KIO3 Standard solution as reference. Beer＇s law was kept in the range of 0. 002 7-0. 686 mg/L dissolved oxygen. The apparent molar absorption coefficient was 4.012×10^4L·cm^-1· mol^-1.The detection limit was 0.001 0 mg/L. In analyzing different water samples, results obtained by this method were in consistency with the results obtained by iodometry and by the dissolved-oxygen determinator.