Development of 1,3-Oxazinoquinolin-4-one-based Derivatization Reagents for the Discrimination of Amine Analytes via...

We designed and synthesized novel precolumn derivatization reagents exhibiting a 1,3-oxazinoquinoline-4-one (Oq) structure to enable differentiation of amine types using quadrupole orbitrap high-resolution mass spectrometry (MS/MS). The developed Oq reagents successfully derivatized amine compounds in aqueous samples under mild basic conditions. Particularly, Oq1─a reagent featuring nitrophenyl-activated ester tethered with glycine linkage─clearly distinguished primary amines, secondary amines, and amines bearing other basic moieties, based on the generation of characteristic positive fragment ions at m/z 190 and m/z [M + H - 171]. We therefore propose the use of the logarithmic value of the fragment ion ratio (logFIR) between m/z 190 and m/z M + H - 171] after derivatization with Oq1 as a quantitative index. Among the 28 tested amino compounds, the estimated ranges of logFIR were 0.03 to 1.6 for primary amines, -0.02 to -1.3 for secondary amines, and -1.2 to -2.4 for amines bearing other basic moieties. Therefore, Oq1 enables differentiation of amine classes based on the fragmentation patterns and corresponding logFIR values. To demonstrate its applicability, Oq1 was employed for the nontarget analysis of components in natural orange juice. The results showed that the logFIR values enhanced the accuracy of component identification. This derivatization strategy offers a powerful tool for amino group analysis via liquid chromatography-MS/MS, potentially advancing qualitative multicomponent profiling in complex matrices.