Magnetic Molecularly Imprinted Polymers for Extraction of Four Amphetamine-Type Stimulants From Sewage and Urine

Magnetic molecularly imprinted polymers (MMIPs) were synthesized by bulk polymerization using N-methylphenethylamine as a dummy template for selective extraction of four amphetamine-type stimulants (ATSs) in sewage and urine. The MMIPs were characterized by scanning electron microscopy, vibrating sample magnetometer, Fourier transform infrared spectroscopy and thermogravimetric analysis, revealing a porous structure (35-60 µm) with a saturation magnetization of 1.8 emu/g, enabling rapid magnetic separation within 1 min. Adsorption kinetics followed a pseudo-second-order model, achieving over 80% adsorption within 10 min and an imprinting factor of 2.4-3.3, demonstrating high selectivity for ATSs over structural analogs. Optimized magnetic solid-phase extraction (MSPE) conditions yielded recoveries over 81% with relative standard deviation (RSD) below 5.5%. Coupled with high performance liquid chromatography-tandem mass spectrometry, the proposed MMIPs-MSPE method exhibited a linear range of 1-100 ng/mL, low detection limits (5.2-19 ng/L), and quantification limits (17.0-65.0 ng/L). The pre-concentration factor of ATSs was 19.3-19.9. Successful application to real sewage and urine samples confirmed robust matrix interference resistance and reliability (recoveries: 82.1%-116%, RSD < 6.4%). This study provides a sensitive, reusable, and environmentally friendly approach for monitoring ATSs in environmental and forensic matrices.