邻甲基苯基重氮氨基偶氮苯光度法测定镉

Spectrophotometric determination of cadmium with о-methylbenzenediazoaminoazobenzene

对分光光度法测定镉（Ⅱ）进行探讨。在非离子表面活性剂TritonX-100存在下及0.08mol/L的氨水介质中,新显色剂邻甲基苯基重氮氨基偶氮苯（о-MDAA）与镉发生灵敏的显色反应,生成络合比为2∶1的红色络合物,其最大吸收峰位于524 nm处。在25 mL显色溶液中,镉量在0-5μg之间符合比尔定律,其表观摩尔吸光系数为1.68×105L·mol^-1·cm^-1。在体系中加入柠檬酸三钠,试剂的选择性好,在大量铜离子存在下,不影响о-MDAA与镉的显色反应。方法用于铜合金及纯铜中镉的测定,相对标准偏差为1.02%-2.31%。

A spectrophotometric method for the determination of cadmium （Ⅱ） is described. The method is based on the color reaction between cadmium and a new chromogenic reagent o-methylbenzenediazo-aminoazobenzene （o-MDAA）. o-MDAA reacts with Cd（Ⅱ） to give a reddish complex with molar ratio of 2：1（R：Cd） in the 0.08 mol/L ammonia solution and in the presence of non-ionic surfactant TritonX-100. The maximum absorption wavelength of the complex is at 524 nm. Beer＇s law is obeyed in the concentration range of 0 to 5μg for Cd（Ⅱ） in 25 mL solution and the apparent molar absorptivity is found to be 1.68×105L·mol^-1·cm^-1. Selectivity of this method is improved by the addition of sodium citrate, and the color reaction isn＇t affected by a great deal of copper（Ⅱ） existed. The proposed method has been successfully applied to the determination of cadmium in copper alloy and pure copper samples, giving relative standard deviation （RSD） from 1.02% to 2.31%.