Efficacious and environmentally friendly deep eutectic solvent-based liquid-phase microextraction for speciation of Cr(III) and Cr(VI) ions in food and water samples
Marziyeh Fasihi, Maryam Rajabi, Behruz Barfi, S. Maryam Sajjadi
Abstract
A rapid, sensitive, and environmentally friendly air-assisted emulsification microextraction based on a deep eutectic solvent was developed for speciation of trace amounts of Cr6+ and Cr3+ ions in real samples. 1-(2-pyridylazo)-2-naphthol was used as a complexing agent and the decomposable and environmental friendly choline chloride-phenylethanol extraction solvent (ChCl:Ph-EtOH) was used as the extraction solvent. The resulting hydrophobic complex, i.e. Cr3+-1-(2-pyridylazo)-2-naphthol, was extracted into the extraction solvent by the air-assisted emulsification microextraction method, followed by its determination with flame atomic absorption spectrometry (FAAS). Different parameters affecting the extraction efficiency, including pH of the sample solution, ratio of the complexing agent to the analyte, number of extraction cycles and volume of the extraction solvent, were optimised using response surface methodology based on the central composite design (RSM-CCD). Under the optimum experimental conditions, the calibration curve was linear in the range of 1.0–300.0 ng mL−1 Cr3+ with a correlation coefficient of 0.997. The relative standard deviation (RSD) based on five replicate analyses of 200.0 ng mL−1 of Cr3+ ions was 4.7%, the limit of detection was 0.4 ng mL−1 (n = 5) and the preconcentration factor (PF) was 39. In order to check the applicability of the method, the chromium ions were determined in tap water and rice, as the model samples. Based on the results obtained, the proposed method was successfully used to determine the chromium species in different water and food samples.