Room temperature ionic liquid-based dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometry for the speciation of chromium(III) and chromium(VI)

Abstract

A simple method for the speciation of chromium(III)/chromium(VI) by flame atomic absorption spectrometry (FAAS) after room temperature ionic liquid (1-octyl-3-methylimidazolium hexafluorophosophate, [C8MIM][PF6])-based dispersive liquid–liquid microextraction (DLLME) was developed. Chromium(VI) and total chromium (Cr(VI) and Cr(III)) could be extracted by [C8MIM][PF6] at the pH value of 5.0 and 6.5, respectively. The Cr(III) content was calculated by subtracting Cr(VI) from the total chromium. The main factors of DLLME were investigated. Under the optimized conditions, the detection limits (3σ) for Cr(III) and Cr(VI) were 1.00μgL−1 and 0.41μgL−1. The relative standard deviations (RSDs) for Cr(III) and Cr(VI) were 3.3% and 4.0% (n=5, c=80.00μgL−1), respectively. The calibration curve exhibited linearity over the concentration range of 5.00–200μgL−1 and 3.00–800μgL−1 for Cr(III) and Cr(VI). The proposed method was validated by the speciation of Cr(III)/Cr(VI) in certified reference materials for environmental water sample and real samples with satisfactory results.