5-Br-PADAP浊点萃取分光光度法测定水样中的痕量铜

Determination of trace Cu(Ⅱ) in river water by spectrophotometry after cloud point with 5-Br-PADAP

目的测定三明市沙溪河水中的痕量铜,有助于监测河水污染情况。方法在表面活性剂Triton X-114存在下,利用5-Br-PADAP{2-（5-bromo-2-pyridylazo）-5-diethylaminophenol}与Cu（Ⅱ）产生显色反应的性能,采用浊点萃取-分光光度法测定水样中的痕量铜。结果在pH=6.8的磷酸体系缓冲液中,Cu（Ⅱ）与5-Br-PADAP形成配合物,其最大吸收波长λmax=556 nm,ε=3.204×10^5L·mol-1.cm-1,检测限为0.011 2μg.mL-1,铜含量在0～0.4μg.mL-1范围内服从比尔定律,并探讨了影响浊点萃取的因素。结论该方法有较好的选择性,具有低毒、高效、安全、简便等特点,直接用于水样中痕量铜的测定,共存离子的干扰完全可以忽略不计,测定结果令人满意,6次重复测定相对标准偏差为1.01%。

Aim To determine trace Cu（ Ⅱ ） in water from Shaxi River, Sanming City, Fujian, China and help to monitor pollutants in the river. Methods The cloud point method was proposed to extract and preconcentrate Cu（ Ⅱ ） in the river water. At pH 6：8 phosphoric acid buffer solution, the analyte Cu（ Ⅱ ） is complexed with 5-Br-PADAP { 2-（5-bromo-2-pyridylazo）-5-diethylaminophenol}. Triton X-114 is added as a surfactant, in the presence of Triton X-114 the complex is soluble in water. The enriched analyte was determined by spectrophotometric methods. Results The maximum wavelength of absorption of the complex is 556 nm, e= 3. 204 × 10^5L·mo1^-1· cm^-1. The detection limit is 0. 011 2 μg· mL^-1. Analytical graphs are linear relation in the concentration range of 0～0.4 μg· mL^-1. Conclusion The method is sensitive, stable, simple, reproducible and relatively free from interference from co-existing species. It was successfully applied to the determination of Cu（ Ⅱ ） in every kinds of water samples. The analytical results of synthetic samples are satisfactory, with relative standard deviations of six determinations of 1.01%.