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Abstract Spontaneous ionization/breakup of water at the surface of aqueous droplets has been reported with evidence ranging from formation of hydrogen peroxide and hydroxyl radicals, indicated by ions atm/z36 attributed to OH⋅‐H₃O⁺or (H₂O‐OH₂)⁺⋅ as well as oxidation products of radical scavengers in mass spectra of water droplets formed by pneumatic nebulization. Here, aqueous droplets are formed both by nanoelectrospray, which produces highly charged nanodrops with initial diameters ~100 nm, and a vibrating mesh nebulizer, which produces 2–20 μm droplets that are initially less highly charged. The lifetimes of these droplets range from 10s of μs to 560 ms and the surface‐to‐volume ratios span ~100‐fold range. No ions atm/z36 are detected with pure water, nor are significant oxidation products for the two radical scavengers that were previously reported to be formed in high abundance. These and other results indicate that prior conclusions about spontaneous hydroxyl radical formation in unactivated water droplets are not supported by the evidence and that water appears to be stable at droplet surfaces over a wide range of droplet size, charge and lifetime. 

Laser-heated electrospray ionization with mass spectrometry enables melting temperature measurements of aggregation-prone proteins from which thermochemical and mechanistic information about protein unfolding and ligand loss is deduced. 

A recently developed method enables the loss of individual charges from 1 to 10 MDa salt clusters to be resolved using charge detection mass spectrometry. This technique is well suited for investigating the mechanics of late stage ion formation.