Polydopamine-Coated Magnetic Nanoparticles for Enrichment and Direct Detection of Small Molecule Pollutants Coupled with MALDI-TOF-MS

Polydopamine-coated Fe3O4 nanoparticles (Fe3O4@PDA NPs) were synthesized and applied as matrix for the detection of pollutants by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The synthesis of Fe3O4@PDA NPs was accomplished in 30 min by in situ polymerization of dopamine without any toxic reagent. Using Fe3O4@PDA NPs as matrix of MALDI-TOF, eleven small molecule pollutants (molecular weight from 251.6 to 499.3), including Benzo(a)pyrene (BaP), three perfluorinated compounds (PFCs), and seven antibiotics, were successfully detected in either positive or negative reflection mode without background interference. Furthermore, the Fe3O4@PDA NPs can also enrich trace amounts of hydrophobic target, such as BaP, from solution to nanoparticles surface. Then the Fe3O4@PDA-BaP can be isolated through magnetic sedimentation step and directly spotted on the stainless steel plate for MALDI measurement. With Fe3O4@PDA NPs as adsorbent and matrix, we also realized the analysis of BaP in tap water and lake water samples. Thus, a magnetic solid-phase extraction (MSPE)-MALDI-TOF-MS method was established for the measurement of BaP.