Solution decomposition of deep eutectic solvents in pH-induced solidification of floating organic droplet homogeneous liquid–liquid microextraction for the extraction of pyrethroid pesticides from milk

Abstract

In this study, a pH-induced solidification of floating organic droplet homogeneous liquid–liquid microextraction procedure using deep eutectic solvent decomposition was developed for the extraction of five pyrethroid insecticides from milk samples prior to their analysis by using a gas chromatography-flame ionization detector. To reach this goal, the sample was transferred into a glass test tube and its proteins were precipitated with trichloroacetic acid. After centrifugation, the supernatant phase was transferred into another test tube and a few microliters of menthol: p-aminophenol deep eutectic solvent were dissolved in the solution and shaken to obtain a homogeneous solution. Then a few microliters of ammonia solution were added to the solution and the mixture was sonicated to break down the homogeneous solution. By doing so, the deep eutectic solvent was decomposed and menthol was formed throughout the solution as tiny droplets. In the following, the tube was transferred into an ice bath to solidify the extraction solvent on the solution surface. The collected phase was removed and melted at room temperature and an aliquot of it was analyzed by using a determination system. The validation outcomes confirmed that the method provides high extraction recoveries (72–84%) and high enrichment factors (257–299) with acceptable repeatability (relative standard deviations ≤6.4%). Low limits of detection (1.1–2.4 ng mL⁻¹) and quantification (3.6–8.1 ng mL⁻¹) were obtained using this approach. Finally, several milk samples were analyzed and deltamethrin was successfully determined in some samples.