5-(5-氟-2-吡啶偶氮)-2,4-二氨基甲苯与钴显色反应的研究及应用

研究了新合成试剂5-(5-氟-2-吡啶偶氮)-2,4-二氨基甲苯(5-F-PADAT)与钴(Ⅱ)的显色反应。实验表明,在pH4.7~9.0范围内,钴与试剂形成紫红色配合物,其最大吸收波长位于506 nm。该配合物在无机酸作用下,可转化为另一具有较高吸收特性的质子化型体,最大吸收波长红移到565 nm,适宜的酸浓度范围分别为:0.24~3.6 mol/L HClO4、0.16~3.84 mol/L H2SO4、0.48~2.4 mol/L HCl、0.64~3.84 mol/L H3PO4。配合物表观摩尔吸光系数ε565=9.1×104L.mol-1.cm-1,钴(Ⅱ)质量浓度在0~0.5μg/mL内符合比尔定律。所拟方法已应用于维生素B12针剂中微量钴的测定。

Study on the color reaction of 5-(5-fluoro-2-pyridylazo)-2,4-diaminotoluene with cobalt and its application

A new method for the spectrophotometric determination of cobalt( Ⅱ) has been developed. In a pH 4.7～9.0 medium, 5-(5-fluoro-2-pyridylazo)-2, 4-diaminotoluene (5-F-PADAT) reacts with cobalt(Ⅱ) to form a violet-red complex exhibiting an maximum absorption at 506 nm. The complex can be changed into another species showing an maximum absorption at 565 ran with addition of mineral acid. This species possesses a higher absorption characteristic . The optimal concentrations of HClO_4, H_2 S0_4, HC1 and H_3 PO_4 are found to be 0.24～3.6 mol/L, 0.16～3.84 vasAIL, 0.48～2.4 mol/L and 0. 64～3. 84 mol/L respectively. The apparent molar absorptivity is e% = 9.1×10~4 L·mol~(-1)·cm~(-1). The Beer's law is obeyed in the range of 0～0.5 μg/mL. This method has the advantages of high sensitivity and selectivity, and has been successfully applied to the determination of cobalt in vitamin B_(12) with satisfactory results.