2-(2，4-咪唑偶氮)-5-二甲氨基苯甲酸分光光度法测定钴

Spectrophotometric determination of cobalt with 2-(2,4-imidazolylazo)-5-dimethylamino-benzoic acid

研究了新显色剂2-(2,4-咪唑偶氮)-5-二甲氨基苯甲酸(IZDBA)的合成及与钴的显色反应条件。2-氨基咪唑硫酸盐采用亚硝酸盐重氮化后,与间-二甲氨基苯甲酸偶联形成IZD- BA。在pH 8.0的NH_3.H_2O—NH_4Cl缓冲溶液中,IZDBA与Co^(2+)形成组成比为2:1的稳定紫色络合物,其最大吸收波长为610 nm,表观摩尔吸光系数为4.15×10~4L·mol^(-1)·cm^(-1),Co^(2+)质量浓度在0～0.8 mg/L范围内遵守比尔定律。方法具有较好的选择性和灵敏度,可以不经分离直接测定合成工业废水中微量钴,RSD(n=6)为2.2%,加标平均回收率为104.5%。

The synthesis of a new reagent 2-（2,4-imidazolylazo）-5-dimethylamino-benzoic acid （IZDBA）and its color reaction with Co^2＋ were studied. It was found that the reagent reacted with cobalt （Ⅱ）to form a stable purple complex（2 ： 1 by mole）in the buffer solution of NH3·H2O-NH4Cl at pH 8.0. The maximum absorption wavelength and apparent molar absorptivity were found as 610 nm and 4. 15×10^4L·mol^-1·cm^-1,respectively. Beer＇s law was obeyed in the range of 0-0. 8 mg/L for Co^2＋. The method has been used for the direct determination of cobalt in synthetic waste water with the RSD of 2.2%6（n=6） and the recovery of 104.5%（n=6）.