5-NO_2-PACA分光光度法测定微量铜

Determination of Trace Copper by Spectrophotometry Method With 5-NO_2-PACA

研究了新显色剂-2-(5-硝基-4-4-2-吡啶偶氮)-1,8-二羟基萘-3,6二磺酸(5-NO2-PACA)分光光度法测定Cu(Ⅱ)的条件,在pH=8.0的NH3-NH4C l缓冲介质中Cu(Ⅱ)与该试剂形成摩尔比为1∶2的紫红色稳定配合物,其最大吸收波长为645 nm,表观摩尔吸光系数为1.43×105L.mol-1.cm-1,Cu(Ⅱ)浓度在0～10 ug/25 mL范围内符合朗伯-比尔定律,并对30多种共存离子对其的影响研究结果表明,常见离子不干扰测定,该方法有较好的选择性,用于奶粉中微量铜的测定,结果满意。

A new spectrophotometric method for the determination of Cu （ Ⅱ ） was developed according to the stud- ies on the conditions of color reaction of a new reagent 2-（5-nitro-2-pyridylazo） -1,8-dihydroxynaphthalene-3,6-dis- ulfonic acid （5-NO2-PACA） with Cu （ Ⅱ ）, which formed a stable fuchsia complex whith mole ratio of 1 ： 2 for Cu （ Ⅱ ） to 5-NO2-PACA in the buffer midium of NH3-NH4C1 pH8.0. The apparent molar absorptivity is 1.43 × 10^3 L · mol^-1 · cm^-1 at the maximum absorption warelength of 645nm. beer＇s law is obeyed in the concentration range of Cu（ Ⅱ ）over 0-10ug/25mL, The results from the investigation on the influence of more than 30 kinds of the coexit ions indicated that most common ions did not interfere in the determination. The method is obvious of good selectivity, was satisfactory used for the determination of trace palladium in milk powder samples with result.