2-(1,3,4-三氮唑偶氮)-5-二乙氨基酚的合成及其与钴显色反应的研究

Synthesis of 2- (1,3,4-Triazolylazo)-5-diethylamino Phenol and Its Color Reaction with Cobalt

合成了新显色剂２－（１，３，４－三氮唑偶氮）－５－二乙氨基酚（ＴＺＡＰＮ），分子式Ｃ１２Ｈ１６ Ｎ６Ｏ，分子量２６０．３１，熔点２０６℃，各级酸离解常数ｐＫａ１＝７．４，ｐＫａ２＝９．９，并研究了它的性质及其与钴显色反应的条件。在ｐＨ７的ＮＨ４Ａｃ介质中，试剂与钴形成络合比Ｃｏ２＋：Ｒ＝１：３的紫红色络合物，此络合物不被强酸分解，其它金属离子与试剂形成的有色络合物能被强酸分解．试剂的λmax＝４３０ｎｍ，钴络合物的λmax＝５４０ｎｍ，Δλ＝１１０ｎｍ，摩尔吸光系数ε＝６．２３×１０4，Ｃｏ２＋在０～０．４ｍｇ／Ｌ范围内遵守比尔定律，所拟方法具有较高的灵敏度与选择性，并直接测定了维生素Ｂ１２、某些合金中痕量钴，回收率为９９．７％～１００．３％，ＲＳＤ（ｎ＝６）为２．０％～２．４％，结果满意．

In this paper, the synthesis of new reagh 2- (1,3,4- triazolylazo) -5-diethylamino phenol (TZAPN), and the condition of spectrophotometric determinagtion of cobalt with this reagent are reported. The results from elemental analysis, UVspectrometric, IR spectroscopic and 1HNMR spectroscopic method show that its structure form is as followswith molecular formula of C12H16N6O, molecular weight of 260.31, mp 206, dissociation constants pKa17.4, pKa29.9. It isbrown crystalline powder and easy to be dissolved in polar solvent. The new reagent reacts with cobalt to form a stablepurple red complex (1: 3) in the pH range of 6.0-8.0 with =430um. However, the complex formed at pH 6-8could be changed into another species of stated absorptivity by addition of mineral acid (1+1). The apparent molarabsorptivity and maximum absorption are 6.23×10·mol-1· cm-1 and 540nm. Beer's law is obeyed in the range of0-0.4mg/L. Many canons and anions do not interfere with the determination of Co2+. The method is highly selective andsensitive, has been applied to the direct determination of trace cobalt in VB12, some alloys and waste water with satisfactoryresults. The recovery is 99.7%-100.3% with precision of 2.0%-2.4% RSD.