Enrichment of Peptides using Novel C₈₋functionalized Magnetic Nanoparticles for Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometric Analysis

C8-functionalized magnetic nanoparticles were synthesized by coating magnetic Fe₃O₄ nanoparticles with silica–amine groups using 3-aminopropyltriethoxysilane and by subsequently modifying the amine groups with chloro(dimethyl)octylsilane to produce octyl groups on the surface of the MNPs. The C₈₋functionalized MNPs were used to enrich peptides from tryptic protein digests of myoglobin and α-casein. The enriched peptides were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI−TOF−MS). MALDI-MS was also used to investigate desalting of the C₈₋functionalized MNPs. Sample solutions were prepared in 1.0 M NaCl, and the successful removal of salt was observed. Enrichment with C₈₋functionalized MNPs was very effective for separating and concentrating tryptic peptides.