Synthesis of a green high density deep eutectic solvent and its application in microextraction of seven widely used pesticides from honey.

A green dispersive liquid-liquid microextraction using a new high density deep eutectic solvent (as an extraction solvent) has been developed and utilized in the simultaneous preconcentration and extraction of seven pesticides in honey followed by gas chromatography-flame ionization detection. The deep eutectic solvent is synthesized using menthol (as a hydrogen bond acceptor) and dichloroacetic acid (as a hydrogen bond donor) at a molar ratio of 1:2. Initially the analytes are extracted into acetone from the sample. After centrifuging, the synthesized deep eutectic solvent is added to the extract obtained from the previous step. Then this mixture is quickly injected into deionized water by a syringe for more concentration. A cloudy solution is formed by dispersion of fine droplets of the deep eutectic solvent by acetone into the aqueous solution and the pesticides are transferred into the extraction solvent. After extraction, phase separation is performed by centrifugation and the enriched analytes in the sedimented phase are determined. The influence of different parameters affecting the extraction efficiency was investigated and optimized. Under the optimized extraction conditions, enrichment factor for the analytes was obtained in the range of 279-428 with extraction recovery of 56-86%. Limits of detection and quantification were obtained in the ranges of 0.32-1.2 and 1.1-4.0 ng g-1, respectively. Relative standard deviations were ≤ 7% for intra- (n = 6) and inter-day (n = 5) precisions calculated at two concentrations of 10 and 50 ng g-1 of each analyte. Finally, some honey samples were effectively analyzed by the proposed method and diazinon was determined at ng g-1 concentration in one sample.