HPLC-FLD determination of aflatoxins M1 and M2 in raw cow milk samples using in-syringe gas-controlled density tunable solidification of a floating organic droplet-based dispersive liquid–liquid microextraction method

Abstract

Herein, an in-syringe gas-controlled density tunable solidification of a floating organic droplet-based dispersive liquid–liquid microextraction method was employed for the extraction of aflatoxin M₁ and M₂ from cow milk samples prior to their quantification with high-performance liquid chromatography equipped with a fluorescence detector. In this method, after precipitating the proteins of the sample using a zinc sulfate solution, the supernatant phase was transferred into a barrel of a glass syringe, with the end closed with a septum containing a mixture of menthol, phenylacetic acid DES (as the extraction solvent), and chloroform (as a density modifier). After that, an inert gas was bubbled into the syringe. In this manner, chloroform was evaporated and fine droplets of extractant were released, which extracted the analytes during their passing. Finally, the syringe was placed in an ice bath and the obtained solidified drop was injected into the separation system after diluting with a mobile phase. Under the best analysis conditions, low limits of detection (1.45 and 1.86 ng L⁻¹ for AFM₁ and AFM₂, respectively) and quantification (4.83 and 6.21 ng L⁻¹ for AFM₁ and AFM₂, respectively), high extraction recovery (75 and 70% for AFM₁ and AFM₂, respectively), and good precision (relative standard deviations ≤ 4.8%) were obtained by employing the approach reported in this study. In the end, this method was successfully employed to determine AFM₁ and AFM₂ in raw cow milk samples collected from Tabriz, Iran.