MOF-derived Oxides Used as MALDI-TOF MS Matrix for the Determination of Amino Acids

Objective: To expand the application of matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) analysis technology in the field of small molecules detection, three metal-organic frameworks (MOFs) derived oxides were synthesized and explored as the novel matrix for efficient analysis of amino acids by MALDI-TOF MS. Methods: Three MOF-derived oxides were synthesized by TiO₂ nano coating modification and calcination, with MOFs as precursors. When MOF-derived oxides used as MALDI matrix, their advantages in the determination of amino acids were studied, the influence of matrix concentration on detection results was explored, and the reproducibility and quantitative analysis ability of the materials were investigated in this study. Results: MOF-derived oxides exhibited better performances compared with MOFs and TiO₂ NPs when detection of proline (Pro), isoleucine (Ile), histidine (His) and tyrosine (Try) under the same detection conditions, including high signal to noise ratio, high ion intensity and good reproducibility. Meanwhile, Cr₂O₃@TiO₂ performed best in three MOF-derived oxides, it had the advantage of a wide linear range (0.001~0.1 mg·mL⁻¹) in quantitative detection of Ile and His, with 0.1 mg·mL⁻¹ of matrix concentration. Conclusion: Four amino acids could be simultaneously and accurately detected by MOF-derived oxides synthesized in this work, these materials had the value of further expansion and application for the detection of amino acids and other small etabolites as MALDI-TOF MS matrix.