An accurate and sensitive method for identifying atmospheric alkylamines: selective enrichment by alkaline...

Alkylamines are emitted from diverse natural and anthropogenic sources, and they play a significant role in new particle formation (NPF) and aerosol growth. However, their accurate quantification in the ambient atmosphere remains analytically challenging due to their strong polarity, low atmospheric concentrations, and susceptibility to adsorption or decomposition. Currently available online and offline analytical techniques have their own advantages and limitations, but none yet fully satisfies the stringent requirements for reliable, speciated measurement of atmospheric alkylamines. In this study, a highly selective and sensitive method tailored to the physicochemical properties of alkylamines (i.e., polarity and alkalinity) was developed by integrating alkaline purging-acidic absorption enrichment with ion chromatography-tandem mass spectrometry (IC-MS/MS). This method enables unambiguous identification of alkylamine species, including isomers such as dimethylamine and monoethylamine, while reducing false positives arising from co-eluting ions in conventional IC analysis and overcoming the limitation of most derivatization-based methods in quantifying tertiary amines. Method detection limits (MDLs) were determined at 9∼94 and 0.1∼1.1 pg·m⁻³ for alkylamines in gaseous and PM_2.5 samples, respectively, representing a substantial improvement in sensitivity over existing offline methods. Field applications in septic tanks and traffic tunnels in Dalian, China, revealed a broader alkylamine speciation profile, including not only monomethylamine, dimethylamine and trimethylamine, but also less monitored species in previous studies, all of which exhibited distinct seasonal concentration variations. This method provides a new analytical choice for trace atmospheric alkylamines and supports quantitative assessment of their contribution to secondary particulate matter formation, particularly PM_2.5.