Enhancing the MALDI-TOF MS Detection Mass Range of Saccharides Using a Reactive Composite Matrix

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis of saccharides, particularly high-molecular-weight polysaccharides, is often hampered by low ionization efficiency. To overcome this limitation, we developed a novel composite matrix comprising 4-hydrazinoquinazoline (4-HQ) and caffeic acid (CA). This matrix synergistically enhances saccharide detection: 4-HQ specifically targets the hemiacetal termini of reducing saccharides via hydrazone formation, thereby improving ionization efficiency, while CA maintains an acidic condition for derivatization and extends the detectable mass range. Using dextran 6 k as a model, we systematically optimized the 4-HQ/CA ratio, reaction temperature, and reaction time. The optimized 4-HQ/CA matrix enabled direct profiling of oligo/polysaccharides in inulin and garlic extracts, as well as N-glycans from ovalbumin and fetuin. Notably, even for non-reducing saccharides where derivatization is precluded, 4-HQ/CA outperformed conventional 2,5-dihydroxybenzoic acid (DHB) by detecting more species with higher signal-to-noise ratios. This versatile composite matrix shows potential for robust analysis of saccharides in glycobiology and food science.