5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯吸光光度法测定微量镍的研究

ABSORPTIOPHOTOMETRIC DETERMINATION OF MICRO AMOUNTS OF NICKEL WITH 5-(5-CHLORO-2-PYRIDYLAZO)-2,4-DIAMINOTOLUENE

在SDS存在下 ,于 pH 5 .5～ 6.5水溶液中 ,5 (5 氯 2 吡啶偶氮 ) 2 ,4 二氨基甲苯 (5 Cl PADAT)与镍 (Ⅱ )形成稳定的紫红色配合物 ,其最大吸收波长位于 5 4 5nm处 ,表观摩尔吸光系数为 1.0 2× 10 5L·mol- 1·cm- 1,配合物中镍与试剂的组成比为 1∶2 ,镍浓度在 0～ 4 μg/ 10ml范围内服从比耳定律。在硫脲、氟化铵和焦磷酸钠存在下 ,方法具有良好的选择性 ,用于镁合金、矿样和钢样中微量镍的测定 。

In this paper, the optimum conditions of the color reaction of 5 (5 chloro 2 pyridylazo) 2,4 diaminotoluene (5 Cl PADAT) with Ni(Ⅱ) are reported. It is shown that 5 Cl PADAT reacts with Ni(Ⅱ) ion to form a stable purple colored (mole ratio 1∶2) complex in an HOAc NaOAc medium of pH 5.5～6.5. The absorption maxima of the complex is at 545nm in the presence of SDS. Its apparent molar absorptivity is 1.02×10 5L·mol -1 ·cm -1 . Beer′s law is obeyed in the concentration range of 0～4μg/10ml of Ni(Ⅱ). The selectivity of the reaction is improved by the addition of thiourea, NH 4F and Na 4P 2O 7 as masking agents. The proposed method has been applied to the determination of nickel in magnesium alloys, ores and steel with satisfactory results.