在pH 4.0介质中,以二乙基二硫代氨基甲酸钠(DDTC)为螯合剂,铁与DDTC生成疏水性螯合物,加入Triton X-114表面活性剂用浊点萃取分离富集怀药中微量铁。表面活性剂相用0.01 mol·L-1盐酸溶液定容至0.6 mL后,所得溶液直接用火焰原子吸收光谱法进行测定。对影响浊点萃取的因素和共存离子的干扰进行了试验并予以优化。铁的检出限(3σ)为0.4 μg·L-1。应用此法测定了怀药(怀山药、怀地黄、怀牛膝、怀菊花)中铁的含量,用标准加入法进行方法的回收试验,测得回收率在90.7%~111.2%之间,测定值的相对标准偏差(n=6)在2.5%~4.5%之间。

Trace amount of Fe was separated and enriched from the sample solution buffered at pH 4.0 in the form of hydrophobic coordination complex with DDTC by cloud point extraction using Triton X-114 as surfactant.The surfactant phase was diluted and made up to 0.6 mL with 0.01 mol·L-1 HCl and the content of Fe was determined by FAAS. Influential factors to cloud point extraction, and interferences of co-existing ions were studied and optimized. Detection limit (3σ) of the method was found to be 0.4 μg·L-1. The proposed method was applied to the determination of Fe in samples of Huaiqing Chinese medicines (Huaiqing Chinese yam, radices rehmanniae, achyranthes and chrysanthemum), and values of recovery obtained by standard addition method were in the range of 90.7%-111.2% with RSD′s (n=6) in the range of 2.5%-4.5%.