Abstract

Magnetic dispersive microsolid phase extraction (MDMSPE) was coupled with dispersive liquid–liquid microextraction (DLLME) for the separation and preconcentration of arsenic(V) and arsenic(III) prior to graphite furnace atomic absorption spectrometry detection. In the first step, magnetic ZnFe₂O₄ nanotubes were employed for adsorbing arsenic(V). The adsorbent was separated from the aqueous phase by the use of an external magnetic field. Next, arsenic(III) in the upper aqueous phase from MDMSPE was enriched by DLLME. Samples were prepared with artificial gastric juice to avoid inter-conversion of the determined species. The parameters affecting the separation and preconcentration of the determined species were optimized. The detection limits of this protocol were determined to be 1.3 and 2.0 pg mL⁻¹ for arsenic(III) and arsenic(V) with relative standard deviations of 4.5% and 5.6% for a concentration of 1.0 ng mL⁻¹ (n = 9). The enrichment factors were equal to 175-fold for arsenic(III) and 163-fold for arsenic(V). The developed protocol was employed for the determination of arsenic(III) and arsenic(V) in dairy products without preoxidation or prereduction. The recoveries of spiked samples were from 90.8% to 105%. A milk powder certified reference material was analyzed by this approach and the measured results were in good agreement with the certified value.

摘要

磁分散微固相萃取 (MDMSPE) 与分散液-液微萃取 (DLLME) 相结合，用于在石墨炉原子吸收光谱检测之前分离和预浓缩砷 (V) 和砷 (III)。第一步，磁性ZnFe ₂ O ₄纳米管用于吸附砷（V）。通过使用外部磁场将吸附剂与水相分离。接下来，来自 MDMSPE 的上层水相中的砷 (III) 被 DLLME 富集。用人工胃液制备样品以避免所确定物种的相互转化。优化了影响确定物质分离和预浓缩的参数。对于砷 (III) 和砷 (V) ，该方案的检测限确定为 1.3 和 2.0 pg mL ^{- 1}，相对标准偏差为 4.5% 和 5.6%，浓度为 1.0 ng mL ^{- 1}（n = 9）。砷 (III) 的富集因子等于 175 倍，砷 (V) 的富集因子是 163 倍。所开发的方案用于测定乳制品中的砷 (III) 和砷 (V)，无需预氧化或预还原。加标样品的回收率为 90.8% 至 105%。采用该方法对某奶粉有证标准物质进行分析，测定结果与标准值吻合较好。