Natural deep eutectic solvent–functionalized mesoporous graphitic carbon nitride–reinforced electrospun nanofiber: a promising sorbent in miniaturized on-chip thin film micro-solid-phase extraction prior to liquid chromatography–tandem mass spectrometry for measuring NSAIDs in saliva

To meet the needs of developing efficient extractive materials alongside the evolution of miniaturized sorbent–based sample preparation techniques, a mesoporous structure of g-C₃N₄ doped with sulfur as a heteroatom was achieved utilizing a bubble template approach while avoiding the severe conditions of other methods. In an effort to increase the number of adsorption sites, the resultant exfoliated structure was then modified with thymol-coumarin NADES as a natural sorbent modifier, followed by introduction into a nylon 6 polymer via an electrospinning process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Brunauer–Emmett–Teller (BET) surface area analysis validated S-doped g-C₃N₄ and composite production. The prepared electrospun fiber nanocomposite, entailing satisfactory processability, was then successfully utilized as a sorbent in on-chip thin film micro-solid-phase extraction of non-steroidal anti-inflammatory drugs (NSAIDs) from saliva samples prior to liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis. Utilizing a chip device, a thin film μ-SPE coupled with LC–MS/MS analysis yielded promising outcomes with reduced sample solution and organic solvents while extending lifetime of a thin film sorbent. The DES-modified S-doped g-C₃N₄ amount in electrospun was optimized, along with adsorption and desorption variables. Under optimal conditions, selected NSAIDs were found to have a linear range of 0.05–100.0 ng mL⁻¹ with an R² ≥ 0.997. The detection limits were ranged between 0.02 and 0.2 ng mL⁻¹. The intra-day and inter-day precisions obtained were less than 6.0%. Relative recoveries were between 93.3 and 111.4%.