镉是一种高毒而且具有蓄积性的重金属, 在环境中含量较低, 需要灵敏的监测技术进行测定。研究了双显色体系测定镉的方法, 对于Cd-邻二氮菲-溴酚蓝形成的三元络合体系, 首先用三氯甲烷萃取, 然后加入碳酸钠解析, 解析出来的溴酚蓝可与丁基罗丹明B形成染料离子对, 该离子对被甲苯萃取, 并用乙醇等色。在589nm测定溴酚蓝 -丁基罗丹明B等色染料离子对的吸光度, 该方法摩尔吸光系数可达到 4.08×10⁵L/(mol·cm), 在 6.0× 10^-8～ 3.1×10^-5mol/L范围内服从比尔定律, 样品标准加入回收率为 98.0%～101.8%, 相对标准偏差为3.2%, 利用该高灵敏度体系测定了三个化工废水样品的镉, 结果令人满意。

Cadmium is one of the heavy metals which have high toxicity and can be accumulated in bodies. Its content in environment is very low. In the determination of Cd, high sensitivity is required. A new detection method formed by two kinds of dye has been studied. Three components system of Cd-Phen-Bromophenol Blue(BPB) is first extracted by CHCl₃. Then the solution of Na₂CO₃ is added to destroy the three components system. Then Butylrhodamine B (BRB) is added to form dye ion pair with BPB. BPB-BRB ion pair is extracted by toluene. The absorbance is measured at 589 nm. The apparent molar absorptivity is 4. 08×10⁵ L/(mol·cm). Beers law is obeyed over the concentration range of 6. 0×10^-8 ～3. 1×10^-5 mol/L. The recovery rate is in the range of 98.0%～101.8%. RSD is 3.2%. The proposed method is applied to the determination of trace Cd in wastewater samples, and satisfactory results have been obtained.