在pH 8.0缓冲溶液中,以8-羟基喹啉为螯合剂,镁、锌和铜均与8-羟基喹啉生成螯合物,加入Triton X-100表面活性剂用浊点萃取分离富集菠菜样品中镁、锌和铜。分取部分表面活性剂相用乙醇定容至25 mL,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等进行了试验并予以优化。镁、锌和铜的检出限(3s/k)依次为0.057,0.064,0.032 mg·L-1。应用此法测定了大叶菠菜和小叶菠菜中3种元素的含量,在两种样品中用标准加入法进行方法的回收试验,测得镁的回收率在93.3%~100.5%之间;锌的回收率在91.7%~97.9%之间;铜的回收率在94.0%~107.1%之间。

Trace amount of Mg(Ⅱ), Zn(Ⅱ) and Cu(Ⅱ) were separated and enriched from the sample solution buffered at pH 8.0 in the form of coordination complexes with 8-oxine by cloud point extraction using Triton X-100 as surfactant. An aliquot of the surfactant phase was diluted and made up to 25 mL with methanol and the contents of Mg, Zn and Cu were determined by FAAS. Factors influential to cloud point extraction, and interferences of co-existing ions were studied. Detection limits (3s/k) of the method were found to be 0.057 mg·L-1 for Mg, 0.064 mg·L-1 for Zn and 0.032 mg·L-1 for Cu. The proposed method was applied to the determination of the 3 elements in samples of big-leaf spinach and small-leaf spinach, and values of recovery obtained by standard addition method were found in the ranges of 93.3%-100.5% for Mg, 91.7%-97.9% for Zn, and 94.0%-107.1% for Cu.