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在十二烷基硫酸钠存在下，于ｐＨ４８～７４的缓冲溶液中，２＿〔２＿（６＿甲基苯并噻唑）偶氮〕＿５＿二乙氨基苯甲酸（６＿Ｍｅ＿ＢＴＡＥＢ）与Ｃｏ（Ⅱ）发生显色反应，形成稳定的蓝紫色络合物，其组成为ｎＣｏ（Ⅱ）∶ｎ６＿Ｍｅ＿ＢＴＡＥＢ＝１∶２，最大吸收波长为６５０ｎｍ，ε为１３８×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，Ｃｏ（Ⅱ）质量浓度在０～０３２ｍｇ／Ｌ时服从比尔定律。方法可直接用于维生素Ｂ１２和含钴分子筛中微量Ｃｏ（Ⅱ）的测定，结果与原子吸收法相符。对于ｗ（Ｃｏ）＝０．８２％的含钴分子筛测定８次，其ＲＳＤ为１３４％。
In the presence of sodium dodecyl sulfate at pH4 8 ~ 7 4 buffer solution, 2_ (2_ (6_ methyl benzothiazole) azo] _5_ diethylamino benzoic acid (6_Me_BTAEB) and Co ) To form a stable blue-violet complex with a composition of nCo (II): n6_Me_BTAEB = 1: 2, a maximum absorption wavelength of 650 nm and an ε of 1 38 × 10 5 L · mol -1 · cm -1 , Beer’s law is obeyed when the mass concentration of Co (Ⅱ) is 0-032 mg / L. The method can be applied to the determination of trace Co (Ⅱ) in vitamin B12 and cobalt-containing molecular sieves. The results are in good agreement with the atomic absorption spectrometry. For the w (Co) = 0.82% cobalt-containing molecular sieve measured 8 times, the RSD was 1.34%.