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)

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 0-20μg/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。

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 ： CA） of 2 to 1 was formed by the reaction of DMCDAA with CA（ Ⅱ ）, having its absorption maximum at 526 nm, and apparent molar absorptivity ε526 of 2. 1 × 10^5 L · mol^-1 · cm^-1. Beer＇ s law was kept in the range of 0-20μg of CA（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 CA（ 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%.