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报道了新试剂２－（５－硝基－２－吡啶偶氮）－５－二甲氨基苯胺（记作５－ＮＯ２－ＰＡＤ－ＭＡ）与钴（Ⅱ）的高灵敏显色反应．实验表明，在ｐＨ４．０～６．２ＨＡｃ－ＮａＡｃ缓冲介质中，试剂可与钴（Ⅱ）形成紫红色配合物，当用高氯酸酸化后配合物转换成一种蓝色稳定的双质子化型体，最大吸收峰位于６１３ｎｍ，摩尔吸光系数为１．１３×１０５Ｌ·ｍｏｌ－１·ｃｍ－１，钴（Ⅱ）浓度在０～３．６μｇ／１０ｍＬ范围内遵守比耳定律．所拟方法已成功地应用于ＶＢ１２针剂、分子筛样品中钴（Ⅱ）含量的测定
A highly sensitive chromogenic reaction of 2- (5-nitro-2-pyridylazo) -5-dimethylaminoaniline (denoted as 5-NO2-PAD-MA) with cobalt (Ⅱ) has been reported. Experiments show that in pH4.0 ~ 6.2HAc-NaAc buffer medium, the reagent can form a fuchsine complex with cobalt (II), and when acidified with perchloric acid, the complex is converted into a blue stable double protonated The maximum absorption peak was at 613 nm, the molar absorption coefficient was 1.13 × 105 L · mol-1 · cm-1, and the Beer’s law was obeyed in the range of 0 ~ 3.6 μg / 10 mL for cobalt (Ⅱ). The proposed method has been successfully applied to the determination of cobalt (Ⅱ) in VB12 injection and molecular sieve samples