显色剂2,5-二甲氧基-4-氯苯基重氮氨基偶氮苯的合成及其与镉显色反应的研究

STUDY OF THE SYNTHESIS OF A NEW CHROMOGENIC REAGENT 2,5-DIMETHOXY-4-CHLOROBENZENEDIAZOAMINOAZOBENZENE AND ITS COLOR REACTION WITH CADMIUM(Ⅱ)

摘要: 合成了显色剂2,5-二甲氧基-4-氯苯基重氮氨基偶氮苯(DMCDAA),并用元素分析和红外光谱分析证明其分子组成与结构.研究了该试剂与镉(Ⅱ)的显色反应条件.结果表明,在pH 11.5的硼砂-氢氧化钠缓冲溶液中,表面活性剂Triton X-100存在下,DMCDAA与镉(Ⅱ)形成稳定的组成比为2∶1的络合物,λmax=526 nm,ε526=2.1×105L·mol-1·cm-1.镉(Ⅱ)含量在0-20 μg/25 mL内符合比耳定律,回归系数为0.999 6.将方法用于铝合金中镉(Ⅱ)的测定,结果的RSD均小于2.5%,回收率在104%-106%之间.

Abstract: A new chromogenic reagent,2,5-dimethoxy-4-chlorobenzenediazoaminoazobenzene (DMOCDAA) was synthesized,and its molecular composition and structure were analyzed and verified by elementary analysis and IR-spectrometry.In a borate buffer of pH 11.5,and in the presence of Triton X-100,a stable complex with mole ratio (R∶Cd) of 2 to 1 was formed by the reaction of DMCDAA with Cd(Ⅱ),having its absorption maximum at 526 nm,and apparent molar absorptivity ε526of 2.1×105L·mol-1·cm-1.Beer′s law was kept in the range of 0-20 μg of Cd(Ⅱ) per 25 mL of solution.The linear regression equation was given as follows: A=0.012 1+0.074 3 C (r=0.999 6),where C denotes μg of Cd(Ⅱ) per 25 mL solution.This method has been used for the determination of cadmium in aluminum alloys,giving RSDs less than 2.5%,and recoveries in the range of 104%-106%.