浊点萃取–火焰原子吸收光谱法分析水样中铬的存在形态

Determination of Chromium Species in Water by Cloud Point Extraction–Flame Atomic Absorption Spectrometry

将浊点萃取与火焰原子吸收光谱法联用对水样中铬的形态进行检测，在pH 7.7条件下，络合剂1-（2-吡啶偶氮）-2-萘酚（PAN）只与Cr（Ⅲ）络合而不与Cr（Ⅵ）反应，实现了环境水样品中Cr（Ⅲ）与Cr（Ⅵ）的分别测定。对影响浊点萃取效率的主要因素如酸度、试剂量、反应温度、时间等进行了研究，在最佳条件下，铬富集倍数为20倍。Cr（Ⅲ）的质量浓度在0.005~1.0 mg/L内与吸光度线性良好，线性相关系数r=0.9998。用该方法对0.30 mg/L的Cr（Ⅲ）标准溶液平行测定11次，测定结果的相对标准偏差为2.9%，检出限为5.74μg/L。将该法用于自来水、河水、三亚温泉水、工厂污水水中铬的形态分析并进行加标回收试验，回收率为90.0％～106.5%。该法富集倍数高、重现性好，测定结果准确可靠。

Cloud point extraction-flame atomic absorption spectrometry was developed to determine chromiun species in water samples. The proposed method was based on the complexation reaction of Cr（Ⅲ）with PAN at pH 7.7, then Cr（Ⅲ）and Cr（Ⅵ）could be detected respectively. Main factors affecting the complex formation and separation were researched,including acidity,amount of the chelating agent,equilibration temperature, time,and so on. Under the optimized conditions,the enrichment factors was 20. The concentration of Cr（Ⅲ）was linear with the absorbance in the range of 0.005-1.0 mg/L, the correlation coefficient was 0.999 8. The relative standard deviation of measurements results of 0.30 mg/L was 2.9%（n=11）. The detection limit of Cr（Ⅲ）was 5.74μg/L. The method was applied to the determination of Cr in tap water, river water and so on, the recoveries ranged from 90.0%to 106.5%. The method has high enrichment factor,good reproducibility and reliable accuracy.