Engineering fluorine and nitrogen co-doped magnetic organic polymers to enrich and detect amphetamine-type stimulants

The development of sensitive, accurate methods for detecting amphetamine-type stimulants (ATSs) has become increasingly urgent, driven by the pressing need to protect human health and environmental safety. However, achieving efficient, selective detection in complex sample matrices remains a major analytical challenge. Magnetic solid-phase extraction (MSPE) offers notable advantages over conventional methods (e.g., LLE, SPE, and DLLME), including shorter extraction times, simpler procedures, and more rapid separation. In this study, a double-shell Fe₃O₄@SiO₂@5F composite was developed via the deposition of a fluorine- and nitrogen-doped polymer onto Fe₃O₄@SiO₂. The characterization confirmed the successful preparation of the coating and showed that the composite material has an adsorption capacity superior to that of traditional materials. An MRM-based GC-MS/MS method was established, for the enrichment and quantification of six ATSs, including AMP, MATM, PEA, MDA, MDMA and MDEA. This method exhibits good recoveries, with linear correlation coefficients (R²) ranging from 0.9974 to 0.9999. The limits of detection (LODs) and quantification (LOQs) were 0.66-1.11 ng mL^-1 and 1.98-3.30 ng mL^-1, respectively. The adsorption mechanism, explored through theoretical calculations, was consistent with experimental data: kinetics followed the pseudo-second-order (PSO) model, while isotherms followed the Langmuir model. Furthermore, density functional theory (DFT) calculations demonstrated that the adsorption process was synergistically driven by π-π, C-H⋯π, and hydrogen-bonding interactions. The composite demonstrated excellent stability across eight consecutive extraction-desorption cycles. Moreover, its successful use in real environmental water and biological samples confirmed its practical value. This study underscores the significant potential of the developed composite for the reliable monitoring and screening of trace drugs.