Fabrication of MXene/chitosan/polyurea nanocomposite decorated on a graphenized substrate for electro-enhanced solid-phase microextraction of diclofenac followed by its determination using differential pulse voltammetry.

A novel solid-phase microextraction fiber based on MXene-chitosan-polyurea (MXene/CS/EPPU) nanocomposite decorated on a graphenized pencil lead fiber (MXene/CS/EPPU/GPLF) was prepared and utilized for electro-enhanced solid-phase microextraction (EE-SPME) of diclofenac (DCF) in biological samples. After extraction and desorption of DCF, it was determined by differential pulse voltammetry (DPV). For this purpose, the working electrode was prepared by deposition of the mentioned MXene/CS/EPPU nanocomposite onto the graphenized pencil lead. The synthesized SPME fiber was characterized using scanning electron microscopy and X-ray diffraction techniques. The effect of various parameters influencing the extraction and the desorption process were investigated, including applied voltage in the extraction and desorption steps, extraction and desorption times, and pH. The developed method exhibited a rather wide linearity in the range 2-1200 ng mL (R = 0.985) for the determination of DCF in plasma samples. The limit of detection and the limit of quantification for plasma samples were estimated to be 0.58 and 1.9 ng mL based on the 3S/m and 10S/m definitions, respectively. The method's accuracy and applicability have been evaluated by the analysis of plasma samples, leading to the relative recoveries in the range 87.0% and 98.0% with the relative standard deviations lower than 3.1%.