Magnetic Nanoparticles Coated with Ionic Liquid as a Sorbent for Solid Phase Extraction of Chromium(VI) Prior to Its Determination by Electrothermal Atomic Absorption Spectrometry

A simple, sensitive and reliable method for the separation, preconcentration and determination of ultra trace amounts of chromium species has been developed. Chromium(VI) in aqueous sample was reacted with 9-phenyl-2,3,7-trihydroxy-6-fluorone to produce a chelate at pH of 5.0 and extracted onto the magnetic nanoparticles coated with the ionic liquid 1-hexadecyl-3methylimidazolium bromide. The trapped analyte was back extracted using 350 μL of nitric acid solution (2 mol L) and was determined by electrothermal atomic absorption spectrometry. Total chromium was determined by oxidizing Cr to Cr using KMnO4 in acidic media. Under the optimum conditions, the method exhibited a linear dynamic range of 0.01-0.50 μg L with an enhancement factor of 112 and a detection limit of 0.003 μg L for Cr. The coefficient of variation (n = 6) at 0.3 μg L concentration level of Cr was 3.2%.