Functionalized Graphene-Coated Cobalt Nanoparticles for Highly Efficient Surface-Assisted Laser Desorption/Ionization Mass Spectrometry Analysis

Graphene-coated cobalt nanoparticles surface-functionalized with benzylamine groups (CoC-NH2 nanomagnets) were shown to effectively enrich analytes for surface-assisted laser desorption/ionization mass spectrometry (affinity SALDI-MS) analysis. These CoC-NH2 nanomagnets are highly suited for use with affinity SALDI-MS because their mean diameter of 30 nm, high specific surface area of 15 m(2) and high-strength saturation magnetization of 158 emu g(-1) led to efficient extraction of analytes by magnetic separation, which in turn enabled excellent SALDI-MS performance. Surface modification of CoC nanomagnets with benzylamine groups increased the yield of peptide ions and decreased fragmentation of benzylpyridinium ions, so-called "thermometer ions" formed through soft ionization. The CoC-NH2 nanomagnets were used to extract perfluorooctanesulfonate from large volumes of aqueous solutions by magnetic separation, which was identified directly by SALDI-MS analysis with high sensitivity even at the sub-part-per-trillion level (similar to 0.1 ng/L). The applicability of CoC-NH2 nanomagnets in conjunction with SALDI-MS for the enrichment and detection of pentachlorophenol, bisphenol A, and polyfluorinated compounds (PFCs) with varying chain length, which are environmentally significant compounds, as well as small drugs, was also evaluated.