Development of an Adogen-based hydrophobic deep eutectic solvent for green air-assisted liquid-liquid microextraction and ICP-OES determination of U(VI) and Cr(VI) in environmental waters.

This work presents the simultaneous extraction and preconcentration of U(VI) and Cr(VI) using a green and flexible hydrophobic deep eutectic solvent (HDES) composed of Adogen 364 and cinnamic acid (1:1 M ratio) coupled with air-assisted liquid-liquid microextraction (AA-LLME) prior to ICP-OES determination. The developed HDES overcomes several limitations associated with conventional extraction solvents by providing efficient phase separation, low toxicity, emulsion-free operation, and enhanced extraction performance in complex aqueous matrices. Under the optimized conditions, the proposed method achieved a preconcentration factor of 20, with limits of detection of 0.16 and 0.18 μg L-1 for U(VI) and Cr(VI), respectively. Excellent linearity and satisfactory precision (RSD < 2%) were obtained. The applicability of the method was successfully evaluated using industrial wastewater, seawater, groundwater, and river water samples spiked with the target analytes, yielding recoveries between 96.74% and 99.80%, indicating negligible matrix effects and high analytical accuracy. Furthermore, greenness assessment using the Green Analytical Procedure Index (GAPI) and Analytical GREEness Metric (AGREE) confirmed the environmental sustainability of the proposed approach. To the best of our knowledge, this is the first report employing an Adogen 364/cinnamic acid-based HDES in combination with AA-LLME for the simultaneous extraction and determination of U(VI) and Cr(VI) in environmental water samples.