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本文报道了高灵敏度高选择性测镉新试剂——2-氯-4-硝基苯基重氮氨基偶氮苯的合成、纯化及结构鉴定。研究了该试剂在不同表面活性剂存在下的酸性离解行为及其与镉(Ⅱ)的显色反应。实验结果表明,在Triton x-100存在下,于pH7.80的磷酸二氢钾-氢氧化钠缓冲介质中。镉(Ⅱ)可与该试剂形成稳定的红色配合物,其最大吸收波长位于505mm处,摩尔吸光系数为1.57×10~5L·mol~(-1)·cm~(-1)镉量在0～12μg/25mL范围内符合比尔定律。在所拟测定条件下,方法选择性甚佳,只有Ag~+、Hg~(2+)、Cu~(2+)离子产生干扰,可通过加入适当的掩蔽剂予以消除。方法可不经分离直接用于环境水样、工业废水及铝合金标样中痕量镉(Ⅱ)的测定,结果满意。
This paper reports the synthesis, purification and structural identification of 2-chloro-4-nitrophenyldiazoaminoazobenzene, a new reagent for high sensitivity and selectivity of cadmium detection. The acidic dissociation behavior of the reagent in the presence of different surfactants and its color reaction with cadmium (Ⅱ) were studied. The experimental results show that in the presence of Triton X-100 in potassium dihydrogen phosphate-sodium hydroxide buffer at pH 7.80. Cadmium (Ⅱ) can form a stable red complex with this reagent. The maximum absorption wavelength is at 505mm and the molar absorptivity is 1.57 × 10-5L · mol -1 ~ 12μg / 25mL within the scope of Bill’s law. Under the conditions of the proposed method, the selectivity of the method is very good, only Ag ~ +, Hg ~ (2 +), Cu ~ (2+) ions interfere and can be eliminated by adding appropriate masking agents. The method can be directly applied to the determination of trace cadmium (Ⅱ) in environmental water samples, industrial wastewater and aluminum alloy standard samples without separation, with satisfactory results.