Suppression of matrix ions by N-phosphorylation labeling using matrix-assisted laser desorption–ionization time-of-flight mass spectrometry

N-Phosphorylation labeling was utilized to analyze small metabolites using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). The incorporation of a neutral phosphoryl group with high gas-phase proton affinity not only improved the ionization efficiency of the target molecules, but also greatly reduced the matrix background interference.