镉(Ⅱ)-碘化钾-吖啶橙缔合体系光度法测定痕量镉

Spectrophotometric determination of trace cadmium with cadmium(Ⅱ)-potassium iodide-acridine orange association system

在pH3.6 NaAc-HAc缓冲溶液中,Cd2＋与过量的KI和吖啶橙（AO）反应生成稳定的离子缔合物[AO]2[CdI4],体系吸光度明显增强,建立了分光光度法测定痕量镉的新方法。试验了酸度、试剂用量、表面活性剂、温度和时间的影响,确定了最佳测定条件。最大吸收峰位于484 nm,线性范围为0~0.4μg/mL,表观摩尔吸光系数为1.66×105L.mol-1.cm-1,检出限为6.82μg/L。大量的常见离子不干扰测定,MnO4-、Pb2＋、Fe3＋和Hg2＋的干扰可采用抗坏血酸-巯基棉分离去除。方法用于测定河水中镉,结果与原子吸收光谱法一致。相对标准偏差为1.7%~2.0%（n=5）,回收率为98%~100%。

A new spectrophotometric method was developed for the determination of trace cadmium.The method was based on the reaction of Cd2＋ with excess KI and acridine orange（AO）,which forms a stable ion-association complex 2 in NaAc-HAc buffer solution at pH 3.6,resulting in a great enhancement of absorbance in the maximum absorption peak at 484 nm.The optimal conditions including acidity,reagents dosage,surfactant,temperature and time were studied.The linear range was 0-0.4 μg/mL.The apparent molar absorptivity was 1.66×105 L·mol-1·cm-1 and the detection limit was 6.82 μg/L.A great deal of coexistent ions didn＇t interfere with the determination.The interferences of MnO4-,Pb2＋,Fe3＋ and Hg2＋ could be separated by ascorbic acid-thiohydroxy cotton fiber.The method was applied to the determination of cadmium in river water samples.The results well agreed with those obtained using atomic absorption spectrometry（AAS）.The relative standard deviations of 5 determinations were 1.7 %-2.0 % and recoveries were 98 %-100 %.