Electrospray Mass Spectrometric Detection of Products and Short-Lived Intermediates in Aqueous Aerosol Microdroplets Exposed to a Reactive Gas

The intermediates ISO sub(3) super(-) (m/z = 207) and IS sub(2)O sub(3) super(- ) (m/z = 239) generated in aqueous (NaI/Na sub(2)S sub(2)O sub(3)) microdroplets traversing dilute O sub(3) gas plumes are detected via online electrospray mass spectrometry within similar to 1 ms, and their stabilities gauged by collisionally induced dissociation. The simultaneous detection of anionic reactants and the S sub(2)O sub(6) super(2-), HSO sub(4) super(-), IO sub(3) super(-), and I sub(3) super(-) products as a function of experimental conditions provides evidence of genuinely interfacial reaction kinetics. Although O sub(3)(aq) reacts about 3 times faster with I super(-) than with S sub(2)O sub(3) super(2-) in bulk solution, only S sub(2)O sub(3) super(2-) is significantly depleted in the interfacial layers of [I super(-)]/[S sub(2)O sub(3) super(2-)] = 10 microdroplets below [O sub(3)(g)] similar to 50 ppm.