Gold nanoparticles supported onto zwitterionic polymer capillary monoliths meant for efficient enrichment of microcystins in water

The release of microcystin (MCs) in aquatic ecosystems poses a substantial risk to the safety of irrigation and drinking water. In view of the challenges associated with monitoring MCs in water bodies, given their low concentration levels (μg/L to ng/L) and the presence of diverse matrix interferences, there is an urgent need to develop an efficient, cost-effective and selective enrichment technique for MCs prior to its quantification. In this work, a gold nanoparticles (AuNPs)-functionalized zwitterionic polymer monolith was described and further applied for the affinity enrichment of MCs. Monoliths modified with zwitterionic amino acid ligands were synthesized within capillary microchannels as highly permeable porous supports for the immobilization of gold nanoparticles via electrostatic interactions. The structure and morphology of AuNPs-hybrid monoliths were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy, confirming the uniform loading of AuNPs on the polymer matrix while ensuring porous structural stability. The as-prepared hybrid monolith was employed as a sorbent for capillary microextraction (CME) prior to liquid chromatography-mass spectrometry (LC-MS) analysis. The results demonstrated that the functionalization of AuNPs under the protection of zwitterionic polymers markedly enhanced the extraction ability of the monolithic column for MCs. This is attributed to the formation of ligand exchange, hydrophobic interactions, and π-system interactions between MCs and AuNPs, as verified by zeta potential and XPS characterization. The developed CME-LC-MS method exhibited a wide linear range (1-10,000 ng L^-1), a low limit of detection (0.58-1.6 ng L^-1), and satisfactory recoveries (71.0-126.7 %) for three MCs in different ambient water sample matrices. It is evident from these findings that AuNPs-functionalized zwitterionic polymers represent a promising novel material for the efficient adsorption of MCs from aqueous samples.