Hydrophobic deep eutectic solvent-based dispersive liquid–liquid microextraction for the zinc determination in aqueous samples: multivariate study

A simple, rapid, and environment-friendly deep eutectic solvents-based dispersive liquid–liquid microextraction (DES-DLLME) technique has been developed to preconcentrate trace levels of zinc (Zn2+) as a sample preparation step prior to its determination with flame atomic absorption spectrophotometry. Deep eutectic solvent (DES) system of choline chloride (ChCl) and dodecanol efficiently extracted the metal–ligand complex (Zn2+-dithizone). Variables such as temperature, pH, incubation time, the volume of dispersive and extraction solvent, centrifugation rate and time, sample volume, and vortex time affecting the extraction efficacy of the proposed technique were screened by Plackett–Burman design. Central composite design was used for the optimization of significant variables. Under optimum conditions, the limit of detection (LOD) and limit of quantification (LOQ) obtained were 0.09 µg L−1 and 0.30 µg L−1, respectively. The relative standard deviation (RSD) was 6.67% (n = 5) with 99.8% recovery for Zn2+. After validation, the developed method was effectively used for the detection of trace level of Zn2+ in real water samples.