2-[2′-(5-硝基-吡啶)-偶氮]-1,8-二羟基萘-3,6-二磺酸与镍显色反应的研究与应用

Study on color reaction of nickel with 2-[2′-(5-nitro-pyridylazo)]-1,8-dihydroxynaphthalene-3,6-disulfonic acid and its application

研究了新显色剂2-[2’-（5-硝基-吡啶）-偶氮]-1，8-二羟基萘-3，6-二磺酸（简称为5-NO2-PACA）的合成路线和方法，并应用光度法对其与Ni抖的显色反应进行了研究。以5-硝基-2-氨基吡啶为原料制备5-硝基-2-氨基吡啶重氮酸盐中间体，再与变色酸偶联合成了5-NO2-PACA。在pH11．5的NH3·H2O—NH4Cl缓冲介质中Ni^2＋与该试剂在室温下很快形成摩尔比为1：1的蓝色稳定络合物，其最大吸收波长为635nm，表观摩尔吸光系数为1．00×10^5L·mol^-1·cm^-1，Ni^2＋浓度在0～500／mL范围内符合比尔定律，常见离子不干扰测定，该方法用于测定环境水样中微量镍，相对标准偏差为2．6％～3．2％（n=6）。

A new sensitive chromogenic reagent, 2-[2＇-（5-nitro-pyridylazo） ]-1,8- dihydroxynaphtha- lene-3,6-disulfonic acid （5-NO2-PACA）, has been synthesized and used in the spectrophotometric determination of nickel. 5-nitro-2-aminopyridine is used as a crude mterial to prepare a intermediate 5-nitro-2-aminopyridine diazotate, which couples with chromotropic acid to give 5-NO2-PACA. In the buffer solution of NH3 ·H2O-NH4Cl at pHll. 5, 5-NO2-PACA can react with nickel （Ⅱ） immediately at room temperature to form a stable blue complex with mole ratio of 1： 1. The apparent molar absorptivity （ε） is 1.00× 10^5 L ·mol^-1 ·cm^-1 at the maximum absorption wavelength of 635nm. Beer＇s law is obeyed over the nickel concentration range 0-500μg/L. Common foreign ions do not interfere. The proposed method has been applied to the determination of nickel in environmental water samples with RSDs of 2.6 %- 3.2 %.