Optical microscopy. Optical images of sprayed particles were acquired using a homemade setup composed of a CDD camera (Applied Vision Technologies) interfaced with a long-distance optical system (Optem Fusion). The light source was a VSI 220 from Optem. The images were acquired with Vimba software. The system was cooled down by using a Linkam chamber, as reported in the reference. Histograms for particle size determination were obtained using Origin(Pro), Version 2018. Speciation plots to fit theoretical and experimental pKa values were done using MATLAB Version R2022b.