Spectrophotometric determination of zinc in blood and food samples using an air-assisted rapid synergistic-cloud point extraction method based on deep eutectic solvents

At room temperature, an air-assisted rapid synergistic cloud point extraction (AA-RS-CPE) method based on deep eutectic solvent (DES) was presented to determine Zn (II) traces in various samples. Nonanoic acid and L-menthol formed the synergistic reagent (DES) in a 2:1 mol ratio to reduce both time and cloud point temperature. Air cycles were used to maximize recovery and accelerate cloudy solution formation. The 4,4-dimethyl-2,6-dioxo-N-phenylcyclohexanecarbothioamide (DDPCCTA) and TritonX-100 were used as ligand and surfactant, respectively. The validation parameters, including the calibration curve linearity (0.2–900 µg L⁻¹), the limit of detection (LOD = 0.10 µg L⁻¹), the enhancement factor (EF = 120), and the preconcentration factor (PE = 100), were calculated. Additionally, the accuracy of the AA-RS-DES-CPE approach was proved by two certified reference materials (CRMs). Finally, the three greenness tools, the Blue Applicability Grade Index (BAGI), the Sample Preparation Metric of Sustainability (SPMS), and the Analytical Greenness Metric for Sample Preparation (AGREEprep), were used to evaluate the environmental sustainability values, health hazards, and applicability of this method. This approach was improved to be safer and more environmentally friendly than existing methods, with high application potential.