Application of Iron Oxide Nanoparticles in the Surface-Assisted Laser Desorption and Ionization–Mass Spectrometry of Small-Molecule Compounds

Abstract

Iron oxide nanoparticles were applied to the surface-assisted laser desorption and ionization–mass spectrometry (SALDI–MS) of small-molecule compounds, such as oligosaccharides, phytohormones, flavonoids, triglycerides, phospholipids, and amino acids. The spatial distribution of small-molecule compounds in soybean was further studied by using imaging mass spectrometry. After different preparation methods were compared, iron oxide nanoparticles calcined at 300 °C were selected. Results showed that in SALDI–MS analysis, iron oxide nanoparticles were characterized by good stability and low background noise. Analysis was performed in the positive ion mode at the laser energy of 70% with the average spectrum accumulated 30 times. The results showed that iron oxide nanoparticles had good repeatability and sensitivity in the analysis of the abovementioned small-molecule compounds. Four samples, namely, sucrose, abscisic acid, DL-aspartic acid, and 1,2-dipalmitoyl-sn-glycerol-3-phosphorylcholine, were analyzed via SALDI–MS. The spot-to-spot repeatability RSD was less than 2.8%, and the interpoint repeatability RSD was less than 5.2%. The linear correlation coefficient of the four samples was R2 > 0.993 within the concentration range of 0.05–1.0 mg/mL. On the basis of these results, the distribution of small-molecule components in soybean cotyledon, radicle, and germ was analyzed through SALDI–MSI.