研究了新显色剂 2 - (四氮唑偶氮 ) - 5 -二乙氨基苯甲酸 (简称 TTZDBA)与钴的显色反应 ,试剂与钴在 p H3 .5的 HAc- Na Ac缓冲溶液中形成稳定的紫红色配合物 ,其组成比为 Co2 + :TZDBA=1∶ 2 ,λmax=6 2 0 nm;试剂的 λmax为 5 0 0 nm,对比度 Δλ为 1 2 0 nm,配合物表观摩尔吸光系数为 ε=9.1 1× 1 0 4。Co2 +浓度在 0～ 0 .5 mg/L范围内符合比尔定律。配合物形成后在强酸溶液中能稳定存在 ,可消除大量金属离子的干扰 ,有良好的选择性。方法可以不经分离直接测定维生素 B12 和工业废水中的微量钴 ,结果令人满意 The color reaction of 2 - (tetrazolium) - 5 - diethylaminobenzoic acid (abbreviated as TTZDBA) with cobalt was studied. The reagent was reacted with cobalt in HAc - Na Ac buffer solution of p H3 .5 A stable purple complex is formed with the composition ratio of Co2 +: TZDBA = 1: 2 and λmax = 620 nm; the λmax of the reagent is 500 nm and the contrast Δλ is 120 nm, and the apparent molar ratio of the complex Absorbance coefficient ε = 9.1 1 × 10 4. Beer’s law is obeyed in the range of 0 ~ 0.5 mg / L for Co2 + concentration. After the formation of complex in strong acid solution can exist stably, can eliminate the interference of a large number of metal ions, with good selectivity. Method can be directly without determination of trace amounts of vitamin B12 and industrial wastewater cobalt, the results are satisfactory