离子对萃取原子吸收光谱法测定微量Cr(Ⅲ)和Cr(Ⅵ)的研究

ION-PAIR EXTRACTION ATOMIC ABSORPTION SPECTROPHOTOMETRY FOR DETERMINATION OF TRACE CHROMIUM(Ⅲ)AND CHROMIUM (Ⅵ) BYTRI-N-BUTYLPHOSPHATE SYSTEM

本文研究了[TBP-Cr(Ⅵ)3-TBP]·Cl_2离子对的形成和萃取的条件,建立了一种新的高灵敏度测定微量Cr(Ⅲ)和Cr(Ⅵ)的分析方法,并利用反萃取和离子特性反应进一步验证了[TBP-Cr(Ⅵ)_2-TBP]·Cl_2离子对的存在。方法应用于地表水中微量Cr(Ⅵ)和Cr(Ⅲ)的测定,获得了满意的结果。

A ensitive arid accurate method for the determination of Cr(Ⅲ) as well as Cr(Ⅵ) was proposed. Sample was mixed with 2mL of 6.0mol·L^(-1) HCl then extracted with 2.0mL of Tri-n-butylphophate for 2 min The organic phase was analyzed by flame atomic absorption spectropliotometry for Cr(Ⅵ). The presence of Cr(Ⅲ), with its concentration up to 500-fold to Cr(Ⅵ), does not affect the result. Another equal portion of the sample was oxdized with 0.5mL KMnO_4(0.25%)at 100℃ for 5 min in 0.36mol·L^(-1) H_2SO_4 solution,then it was treated with both 2.0 mL of 90% CO(NH_2)_2 and 1% NaNO_2 solution.The total Cr was analyzed and the original Cr(Ⅲ) amount was obtained by difference. For Cr in 0—0.25 Ppm range, the working curves are linear, and the coefficient of variation for 0.20ppm Cr of standard solution is 1.0%(n=12).The 3σ limit for Cr(Ⅵ)is 0.012 ppm, and the sensitivity for 1% absorption due to Cr(Ⅵ) is 0.05 ppm in the TBP solution.