Speciation and determination of chromium by ultrasound-assisted deep eutectic solvent liquid–liquid microextraction followed by flame atomic absorption spectrometry

Abstract

In the present study, an ultrasound-assisted deep eutectic solvent liquid–liquid microextraction (UA-DES-LLME) technique was developed for selective speciation, extraction, and preconcentration of chromium species followed by quantitation by flame atomic absorption spectrometry. The effective parameters of the applied method comprising pH, composition and volume of the deep eutectic, volume of ammonium pyrrolidine dithiocarbamate complexing agent, volume of tetrahydrofuran, time of ultrasonication and centrifugation were optimized. The proposed method at optimum values of all factors was used for determination of Cr(VI). For evaluation of total chromium species, added KMnO4 (strong oxidizing agent) into the sample, and heated for 2 min to convert Cr(III) into Cr(VI) and determined. The Cr(III) concentration was obtained from the difference between Cr(VI) from total chromium. Under the optimal conditions, preconcentration factor (PF), limit of detection (LOD), and limit of quantification (LOQ) were found as 50, 0.8 µg L−1 and 3.2 µg L−1, respectively. The relative standard deviation (RSD %) was found < 5.0%. Finally, the developed method was used for the determination of Cr(VI) and Cr(III) in tea and water samples.