新显色剂2,4,4′-三硝基苯基重氮氨基偶氮苯光度法测定微量镉

Spectrophotometric Determination of Micro Amount of Cadmium(Ⅱ) by a New Reagent 2,4,4′-Trinitrobenzenediazoaminoazobenzene

研究了新显色剂2,4,4′-三硝基苯基重氮氨基偶氮苯(简称TNBDAA)与Cd(Ⅱ)的显色反应。结果表明,在Triton X-100存在下,在pH 7.75-8.75的缓冲范围内,Cd(Ⅱ)与试剂形成摩尔比1∶2的红色配合物,最大吸收波长位于546 nm处,表观摩尔吸光系数为1.38×105L/(mol.cm),镉的浓度在0-0.7μg/mL范围内服从比耳定律。所拟方法操作简便,灵敏度高,选择性好,用于废水中微量镉的直接测定,结果满意。

The colour reaction of a new reagent 2,4,4＇-trinitrobenzenediazoaminoazobenzene （TNBDAA） with cadmium （Ⅱ） was studied. In the presence of Triton X-100, Cd（Ⅱ）reacts with TNBDAA to form a red complex with a molar ratio of 1：2 in a medium of pH 7.75 - 8.75. Its apparent molar absorptivity is 1.38 × 10^5 L ·mol^-1·cm^-1 at 546 nm. Beer＇s law is obeyed in the concentration range of 0 - 0.7 μg/mL for Cd（Ⅱ）. The method has been applied to the determination of cadmium directly in waste water with satisfactory results.