Simultaneous determination of particulate-phase amines and amino acids in urban aerosols: Development of a rapid LC–MS/MS method and application to Seoul PM2.5

• Developing a method for the simultaneous quantification of particle phase 17 alkyl amines and 25 free amino acids • Compound-specific isotope-labeled internal standards via benzoyl chloride-d 5 derivatization • Rapid derivatization enabling efficient analysis of amines and amino acids • Excellent linearity, high recovery and low LOQ • Application to PM 2.5 samples collected in Seoul during winter and spring revealed pronounced seasonal contrasts Organic nitrogen species such as alkyl amines (AAs) and free amino acids (FAAs) are increasingly recognized as important contributors to urban aerosol chemistry and potential health risks, yet their concentrations, sources, and seasonal behaviors remain poorly understood. In this study, we developed a rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the simultaneous determination of 17 AAs and 25 FAAs in PM 2.5 , employing simplified pretreatment and isotope-labeled internal standards. Application to PM 2.5 samples collected in Seoul during winter and spring revealed pronounced seasonal contrasts: AAs were elevated in winter and strongly associated with secondary inorganic species and combustion-related pollutants, while FAAs were more abundant in spring, reflecting enhanced biological activity. Correlation analysis with co-pollutants and meteorological parameters highlighted distinct seasonal emission processes and atmospheric transformations. These findings demonstrate the diverse sources and behaviors of nitrogen-containing organics in urban PM 2.5 and underline their implications not only for nitrogen cycling but also for particulate toxicity, air quality management.