DES-impregnated electrospun nanofiber microextraction for simultaneous determination of carvedilol and verapamil in human plasma by HPLC-fluorescence detection.

The development of efficient and environmentally compatible sample preparation strategies for the determination of pharmaceuticals in complex biological matrices remains an important challenge in bioanalytical chemistry. Herein, a deep eutectic solvent (DES)-impregnated electrospun nanofiber microextraction (DES-ENF-ME) approach was developed for the simultaneous extraction of carvedilol and verapamil from human plasma prior to HPLC-fluorescence detection. A hydrophobic fatty-acid-based DES composed of nonanoic acid and dodecanoic acid (3:1, molar ratio) was selected and impregnated onto electrospun polyacrylonitrile nanofibers. In this configuration, the DES acts as the primary extraction phase, while the nanofibrous matrix provides a porous support for retaining and handling the liquid extraction phase. Sample pH, nanofiber amount, salt concentration, and extraction time were simultaneously optimized using central composite design and a desirability function. The method exhibited a linear response over the range of 1-1000 ng/mL for both analytes, with coefficients of determination of 0.9988 and 0.9942 for carvedilol and verapamil, respectively. The corresponding limits of detection were 0.396 and 0.342 ng/mL. The method showed satisfactory precision and relative recoveries for spiked plasma samples. Moreover, the DES-impregnated nanofibrous material was reusable for at least four consecutive extraction cycles. Overall, the proposed configuration combines the extraction capability of a hydrophobic DES with the practical handling advantages of an electrospun nanofibrous support, providing a simple, miniaturized, and solvent-efficient platform for plasma bioanalysis.