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A new assay based on effective (high recovery) extraction by means of deep eutectic solvents (DESs) was developed for ppb level determination of zinc in fishes and eel samples. Choline chloride and Phenol in a 1:2 M ratio was selected as optimal DES-based extraction solvent. 8-Hydroxy quinoline was used as a chelating agent for zinc ions. The optimized conditions were found at pH value of 8, ligand concentration of 10 mg/L, THF volumetric ratio in bulk solution of 0.5:10. The total time at optimal sample preparation conditions was 5 min for digested sample. Developed method fits to the purpose of routine analysis of fishes and eels. The LOD and LOQ were found 0.041 μg/kg and 0.136 μg/kg with pre-concentration factor of 25 and RSD 1.7%. [Display omitted] • Deep eutectic solvent based extraction of zinc from fish and eel samples. • Green chemistry approach for sample preparation. • FAAS determination of zinc in DES extract. • Novel application of DES in extraction techniques. • LOD at ppb level for zinc analysis. [ABSTRACT FROM AUTHOR]

This paper presents a new analytical procedure based on combination of homogeneous liquid–liquid extraction (HLLE) and vortex-assisted dispersive liquid–liquid microextraction (VA-DLLME) for the accurate and reliable determination of ochratoxin A (OTA) in dried fruit samples. To enable selective extraction of the OTA, six hydrophobic deep eutectic solvents (hDESs) were prepared and tested as extraction solvents. Optimization of DES volume, pH, NaCl amount, and mixing time affecting the efficiency of VA-DES-DLLME step was achieved by central composite design (CCD). Using optimized conditions, the working range was obtained in the range 0.4–350 ng mL−1 with an enrichment factor of 138. The limit of detection was 0.12 ng mL−1. To evaluate the accuracy of the method, the samples were analyzed with both the HLLE-VA-DES-DLLME procedure and reference method. The precision of the method was investigated by intraday/interday studies. The robustness of the method was also evaluated by making minor changes to the optimized conditions. The HLLE-VA-DES-DLLME procedure was successfully applied to dried fruit samples and quantitative recoveries were obtained (92.1–99.2%) confirming its usefulness for implementation in routine analysis of food samples. [Display omitted] • Novel sample preparation microextraction based protocol for OTA determination. • hDES based on hexafluoroisopropanol and carnitine provide best performance. • Application of chemometric approach for method optimization. • Minimization of solvent consumption, high selectivity and method robustness. • LOD, LOQ, and EF were found as 0. 21 ng mL−1, 0.40 ng mL−1, 138 respectively. [ABSTRACT FROM AUTHOR]

• Factors affecting the extraction recovery were optimized by a multivariate protocol. • Magnetic extraction solvent was prepared by mixing octanoic acid, aliquat-336 and CoCl 2. • Centrifugation step was not required to achieve phase separation. • Ease of operation, fast, and simplicity were the main advantages of the method. • The linear range and limit of detection were 3–600 ng mL−1 and 0.9 ng mL−1, respectively. In the current research, a fast and sustainable air-assisted hydrophobic magnetic deep eutectic solvent-based dispersive liquid phase microextraction followed by UV–Vis spectrophotometry measurements was optimized for the extraction and determination of melamine in milk and milk-based products. The central composite design was applied for the optimization of factors affecting the recovery of melamine. Quantitative extraction of melamine was achieved using hydrophobic magnetic deep eutectic solvents prepared from a mixture of octanoic acid, aliquat-336, and cobalt(II) chloride. The optimum conditions for extraction were found as follows: 6 extraction cycles, pH 8.2, extraction solvent volume 260 µL, and acetone volume 125 µL. Interestingly, a centrifugation step was not required to achieve phase separation. Under the optimum conditions, melamine was determined in the linear range of 3–600 ng mL−1, the limit of detection (3S blank /m) of 0.9 ng mL−1, and the enrichment factor of 144. The validation of the method was investigated by the analysis of reference materials. Consequently, the method was successfully applied for the analysis of melamine residues in milk and milk-based products. [ABSTRACT FROM AUTHOR]