Selenium Speciation in Rice Samples by Magnetic Ionic Liquid-Based Up-and-Down-Shaker-Assisted Dispersive Liquid-Liquid Microextraction Coupled to Graphite Furnace Atomic Absorption Spectrometry

A novel and sensitive magnetic ionic liquid-based up-and-down-shaker-assisted dispersive liquid-liquid microextraction (MIL-UDSA-DLLME) was developed for the graphite furnace atomic absorption spectrometric measurement of inorganic selenium speciation from various rice matrixes. In the first microextraction step, the magnetic ionic liquid (1-butyl-3-methylimidazolium tetrachloroferrate, [C4mim][FeCl4]) was selected to extract the complex of Se(IV) and 2,3-diaminonaphthalene from aqueous solution by the assistance of up-and-down-shaker vortex agitator. After the microextraction step, the magnetic ionic liquid containing target analytes was collected at the bottom of the tube by applying an external magnetic field around the test tube. Under the optimized conditions, the method present has low detection limit (0.018 μg L−1), wide linear dynamic range (0.03–10 μg L−1), and good repeatability (<3.0%, n = 10) for Se(IV). The proposed methodology was applied for separation and preconcentration of inorganic selenium in standard reference materials including GBW10010 rice, GBW10043 Liaoning rice, and GBW10045 Hunan rice with satisfactory results. The developed methodology was also successfully used for the speciation of Se(IV) and Se(VI) in different rice samples with the relative recoveries within the acceptable range of 94.9–104.8% for the addition recovery tests.