A composite adsorbent of graphene quantum dots, mesoporous carbon, and molecularly imprinted polymer to extract nonsteroidal anti-inflammatory drugs in milk

Abstract

A composite magnetic adsorbent was developed by embedding graphene quantum dots (GQDs), silica-modified magnetite (Fe₃O₄-SiO₂), and mesoporous carbon (MPC) into a molecularly imprinted polymer (GQDs/Fe₃O₄-SiO₂/MPC/MIP). The adsorbent was applied to extract nonsteroidal anti-inflammatory drugs (NSAIDs) in milk. The MIP was formed via a sol-gel copolymerization using flurbiprofen, diflunisal, and mefenamic acid as template molecules, 3-aminopropyltriethoxysilane as a monomer, and tetraethyl orthosilicate as a cross-linker. GQDs and MPC enhanced affinity binding between NSAIDs and the adsorbent through π-π stacking, hydrogen bonding, and hydrophobic interaction. The Fe₃O₄-SiO₂ nanoparticles embedded in the composite adsorbent enabled its rapid isolation from the sample solution. The extracted NSAIDs were quantified by high-performance liquid chromatography and exhibited good linearity from 1.0 to 100.0 μg L^-1 for flurbiprofen and 0.5 to 100.0 μg L^-1 for diflunisal and mefenamic acid, respectively. The limits of detection ranged from 0.5 to 1.0 μg L^-1. Recoveries of NSAIDs from spiked milk samples ranged from 81.4 to 93.7%, with RSDs below 7%. The reproducibility of the fabricated adsorbent was good and in the optimal conditions, the developed adsorbent could be used for up to six extraction-desorption cycles.

Keywords: Carbon-based nanomaterials; Diflunisal; Flurbiprofen; Graphene quantum dots; Mefenamic acid; Mesoporous carbon; Sorbent extraction.