Hydrophilicity-switchable deep eutectic solvent-based ultrasound-assisted liquid-phase microextraction for the green...

In this study, a hydrophilicity-switchable deep eutectic solvent (HS-DES) was prepared by combining nonanoic acid (C9) with tetrabutylammonium bromide (TBAB) and applied as an efficient extraction medium for the ultrasound-assisted liquid-phase microextraction (UALPME) of verapamil from human plasma samples prior to spectrofluorimetric determination. The hydrophilicity-hydrophobicity transition of the HS-DES was controlled by pH adjustment using NaOH or HCl solutions, enabling reversible phase switching and facilitating effective separation of verapamil from the biological matrix. Key experimental parameters influencing the extraction efficiency were systematically investigated, and further optimization was performed using a central composite design coupled with a desirability function approach. The developed HS-DES-based UALPME (HS-DES-UALPME) method provides a tunable, environmentally friendly, and effective strategy for the preconcentration of verapamil from complex biological samples. The method showed wide linear range (200-2000 ng/mL), a good limit of detection (62.16 ng/mL), and extraction recovery (59.55%). To assess the method's sustainability, the AGREE tool was applied, clearly demonstrated the overall greenness of the developed procedure. A comparison of the analytical performance of the method with previously reported methods demonstrated its superiority or, at minimum, its comparability in key analytical parameters.