新试剂2-(5-碘-2-吡啶偶氮)-5-二甲氨基苯胺 分光光度法测定矿石中的钴

对新试剂2-(5-碘-2-吡啶偶氮)-5-二甲氨基苯胺(5-I-PADMA)与钴(Ⅱ)的显色反应进行试验。结果表明,在pH为4.2~9.2时,钴(Ⅱ)与试剂形成1∶2红紫色配合物,配合物有两个吸收峰,分别位于554 nm和602 nm处;钴配合物形成后非常稳定,当以无机酸酸化,由于质子化作用,配合物转化成另一种具有较高吸收特性绿蓝色稳定的双质子化型体,其吸收峰分别红移至568 nm和614 nm,适宜的酸浓度范围分别为:0.3~7.0 mol/L盐酸、0.3~6.0 mol/L高氯酸、0.3~4.2 mol/L硫酸和0.7~7.3 mol/L磷酸。配合物表观摩尔吸光系数6ε14 nm为1.21×105L/(mol.cm)。钴含量在0~0.5μg/mL内遵循比尔定律。方法简便,快速,且具有良好的选择性,已成功地应用于矿样中微量钴的测定,结果满意。

Spectrophotometric Determination of Cobalt in Ores with a New Regent 2-(5-Iodine-2-Pyridylazo)-5-Dimethylaminoaniline

High sensitive color reaction of a new reagent of 2-(5-iodine-2-pyridylazo)-5-dimethylaminoaniline(5-I-PADMA) with cobalt(Ⅱ) has been studied.In pH 4.2~9.2 medium,5-I-PADMA reacts with cobalt(Ⅱ) to form a violet-red complex exhibiting two absorption peaks at 554 nm and 602 nm respectively.This complex can be changed into another stable blue-green diproton species after acidification with mineral acids,and the two absorption peaks shift to 568 nm and 614 nm respectively.This species possesses a higher absorption characteristic.The optimal acidification conditions were found to be 0.3~7.0 mol/L HCl,0.3~6.0 mol/L HClO4,0.3~4.2 mol/L H2SO4 and 0.7~7.3 mol/L H3PO4,respectively.The apparent molar absorptivity ε614 nm is 1.21×105 L /(mol· cm).Beer′s law is obeyed in the range of 0~0.5 μg/mL for Co.The method provides high sensitivity,high selectivity and less interference.The method has been successfully applied to the determination of cobalt in ores with satisfactory results.