微乳相萃取分离富集-原子吸收光谱法分析铬形态

Speciation Determination of Chromium by Atomic Absorption Spectrometry with Separation of Microemulsion Extraction

建立了一种微乳相萃取分离-石英双缝管原子捕集火焰原子吸收光谱法(STAT-FAAS)分析环境水样中铬形态的新方法。该方法中,Cr(Ⅲ)与8-羟基喹啉反应形成的疏水性配合物,经萃取进入微乳相,Cr(Ⅵ)留在水溶液中,从而实现Cr(Ⅲ)与Cr(Ⅵ)的相互分离。Cr(Ⅵ)含量的测定通过过氧化氢溶液将Cr(Ⅵ)还原为Cr(Ⅲ),按同样方法分析。实验对微乳相萃取的主要影响因素进行了优化。结果表明,经优化后实验条件为:平衡温度80℃,平衡时间10min,溶液酸度pH=9.0,NH3-NH4Cl缓冲溶液用量2.0mL,8-HQ用量0.05mmol;TritonX-100微乳液组成:m(TritonX-100):m(正戊醇):m(正己烷):m(水)=3.0:15:1.5:4.0。在此条件下,萃取的富集倍数达到25倍(50mL起初样品溶液/2mL最终测定液),线性范围为2.5～500μg/L,检出限为0.62μg/L,相对标准偏差(RSD)为3.8%(n=10,c=10μg/L)。本方法已成功地应用于电镀废水中铬形态分析。

A novel method has been developed for the speciation of chromium in environmental water samples based on microemulsion extraction separation and preconcentration,and determination by double-slotted quartz tube atom trap-flame atomic absorption spectrometry （STAT-FAAS）.In this method,Cr （Ⅲ） reacts with 8-hydroxyquinoline（8-HQ） yielding a hydrophobic complex,which then is extracted in the microemulsion phase,whereas Cr（Ⅵ） remained in aqueous phase.Thus,separation of Cr（Ⅲ） and Cr（Ⅵ） could be realized.Total chromium was determined after the reduction of Cr（Ⅵ） to Cr（Ⅲ） by using hydrogen peroxide as the reducing reagent.The main factors affecting the separation of Cr（Ⅲ） and Cr（Ⅵ） were optimized.The optimum conditions of the experiment are as follows,equilibration temperature and time are 80 ℃ and 10 min respectively,the pH of the system is 9.0,amounts of NH3-NH4 Cl buffer and 8-HQ are 2.0 mL and 0.05 mmol,respectively,and microemulsion is made of mixture of Triton X-100,n-pentanol,n-hexane and water at mass ratio of 3.0：15.0：1.5：4.0.Under the optimized conditions,the preconcentration system permitted an enrichment factor of 25 for chromium from the initial 50 mL sample solution to the final 2 mL concentrated solution;the linear concentration range was 2.5 ～ 500 μg/L for chromium.The limit of detection was 0.62 μg/L,and the relative standard deviation（n=10） was 3.8% for 10 μg/L Cr（Ⅲ） solution.The proposed procedure has been applied to the speciation of chromium in electroplating wastewater samples successfully.