Vortex-Assisted Ionic Liquid-Based Liquid-Phase Microextraction: A Simple, Low Cost, and Environmentally Friendly Method for Speciation of Antimony in Water

A sensitive method is proposed to determine antimony species using vortex-assisted ionic liquid-based liquid-phase microextraction and digital imaging colorimetry. Sb^III forms a ternary complex with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol, ascorbic acid, and iodide in an acid medium. The acceptor phase consists of the ionic liquid 1-butyl-3-methylimidazole hexafluorophosphate, dispersed in the aqueous solution with a vortex stirrer. After centrifugation, Sb^III was determined directly in the rich phase. Sb^V can also be measured by converting to reduced species. The method presented a limit of detection of 1.4 and 4.2 μg L^-1 and an enrichment factor of 360. The precision (relative standard deviation) of the method is 7.0%. The procedure was applied to the speciation of antimony in river water and mineral water samples. Some results were compared with those obtained by electrothermal atomic absorption spectrometry (ET AAS). The method is an attractive alternative for determining antimony species, considering the aspects of green analytical chemistry.

Keywords:
liquid phase extraction; antimony; digital image colorimetry; speciation