Chemical ionization mass spectrometry: Developments and applications for on-line characterization of atmospheric aerosols and trace gases

Chemical ionization mass spectrometry (CIMS) is a powerful tool for on-line characterization of atmospheric trace species and reveal of new atmospheric oxidation mechanisms. The applications of CIMS promoted understanding of new particle formation and the roles of trace species in air-quality issues. In the past decade or so, various new techniques in ion sources have been applied to improve sensitivity and replace radioactive sources. Moreover, researchers have developed multiple sampling inlets for CIMS to meet the measurement demand of reactive trace species. In this study, we discussed these developments and reviewed a limited number of representative applications of CIMS, including trace highly reactive gaseous pollutants, aerosols and highly oxygenated organic molecules. In particular, we summarized the choice of reagent ions, the influencing factors of the sensitivity, and the strategies in improving instrument sensitivity. This review summarizes CIMS instrument developments and its applications from an appreciation of instrument technology developing perspectives.