Rapid magnetic solid-phase extraction approach employing a modified graphene oxide nanomaterial for the determination of 20 pharmaceuticals and transformation products in treated urban wastewater

A magnetic solid-phase extraction (MSPE) method based on a green magnetic graphene oxide material (d-M@GO) was developed and validated for the simultaneous determination of 20 contaminants of emerging concern (CECs), including pharmaceuticals and transformation products, in wastewater using liquid chromatography-high-resolution mass spectrometry (LC-HRMS). The adsorption behaviour of analytes on d-M@GO was investigated through kinetic and equilibrium modelling, indicating mass-transfer-limited adsorption consistent with a linear isotherm. A two-zone kinetic model, accounting for fast and slow adsorption regions, provided the best fitting for most compounds, confirming the coexistence of easily accessible and diffusion-limited adsorption sites. The MSPE procedure was optimised to establish the most efficient adsorption and elution conditions. Method validation in treated urban wastewater demonstrated its suitability as a green alternative to conventional solid-phase extraction. Eighteen of the twenty analytes showed recoveries between 70% and 120%, with RSDs below 20%. Low method quantification limits (MQLs) were determined, ranging from 2 to 20 ng/L. Application of the method for the analysis of five wastewater samples enabled the quantification of up to 19 analytes at concentrations ranging from 6.37 to 1321 ng/L. In addition, non-target screening using MS-DIAL open-source software (a platform for untargeted metabolomics and lipidomics data processing) expanded the analytical scope, allowing the tentative identification of 24 additional CECs, five of which were confirmed using reference standards. The combination of target and non-target analyses demonstrates the capability of the method for comprehensive monitoring of CECs in wastewater. With a 60-70% lower carbon footprint than conventional SPE approaches, the d-M@GO-MSPE-LC-HRMS workflow represents a robust, rapid, and sustainable solution.