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-3-methylimidazolium bromide. The trapped analyte was back extracted using 350 mu L of nitric acid solution (2 mol L-1) and was determined by electrothermal atomic absorption spectrometry. Total chromium was determined by oxidizing Cr-III to Cr-VI using KMnO4 in acidic media. Under the optimum conditions, the method exhibited a linear dynamic range of 0.01-0.50 mu g L-1 with an enhancement factor of 112 and a detection limit of 0.003 mu g L-1 for CrVI. The coefficient of variation (n = 6) at 0.3 mu g L-1 concentration level of Cr-VI was 3.2%.