Vortex-assisted liquid-liquid microextraction and indirect spectrophotometric determination of chromium(vi)

A novel, simple, sensitive and selective method for the indirect spectrophotometric determination of chromium(vi) was developed on the basis of vortex-assisted liquid-liquid microextraction (VALLME) of an ion association pair formed between the triiodide anion (I₃ ^-) and cationic dye Astrazone Brilliant Red 4G (ABR). The indirect spectrophotometric determination of chromium(vi) was based on the redox-reaction of Cr(vi) with iodide and formed I₃ ^-. The triiodide anion was determined spectrophotometrically at 530 nm following VALLME of an ion association pair with ABR. The calibration plot was linear in the range 0.050-4.2 μg L^-1 (R ² = 0.998), and limit of detection (LOD) was 0.015 μg L^-1 for Cr(vi). The suggested procedure was successfully applied for the determination Cr(vi) in water samples (RSD 3.3-5.7%, recovery 97.7-102.8% when determining ultratrace levels Cr(vi) at 0.55-5.77 μg L^-1), the accuracy of the method was assessed through a comparison with reference methods and certified reference materials.