Synergistic Effect of Metal-Organic Framework/Gallic Acid in Enhanced Laser Desorption/Ionization Mass Spectrometry

摘要： Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has become an indispensable tool for high throughput analysis of macromolecules, but many challenges still remain in detection of small molecules due to the severe matrix-related background interference in the low-molecular mass ranges (MW < 700 Da). Herein, a gallic acid (GA)-functionalized zirconium1,4-dicarboxybenzene metal-organic framework (MOF) (denoted as UiO-66-GA) was designed to serve as a new substrate and a novel strategy on the basis of the synergistic effect of MOF and GA was developed to enhance LDI process. In comparasion with conventional organic matrices, the UiO-66-GA substrate showed superior LDI performance in the analysis of a wide varity of molecules including amino acids, unsaturated fatty acids, bisphenols (BPs), oligosaccharides, peptides, protein, and polyethylene glycol (PEG) of various average molecular weights from 200 to 10000. Perfluorooctanoic sulfonate (PFOS) was used to evaluate the ability of quantitative analysis and its corresponding limit of detection (LOD) as low as 1 fmol was achieved. High sensitivity and good salt tolerance of the UiO-66-GA-assisted LDI-MS were allowed to determine ultratrace PFOS in the spiked human urine and serum samples. In addition, the synergistic mechanism of MOF and GA in enhanced LDI process was investigated by comprehensively comparing GA- and its analogues functionalized UiO-66, and the results revealed that two aspects contributed to the enhanced LDI process: 1) an enhancement in metal-phenolic coordination system of UiO-66-GA promoted laser absorption and energy transfer; 2) introduction of carboxyl- and hydroxyl groups of GA onto UiO-66 facilitated the LDI process in both positive- and negative ion modes. This work expands a new domain for the MOF applications and provides a promising alternative for various molecule analysis.