title: Correlating droplet size with temperature changes in electrospray source by optical methods.
abstract: We investigated how the temperature and size of charged droplets are affected by the electrospray ionization (ESI) process, using in situ measurements involving laser-induced fluorescence and Mie scattering on a thermal gradient focusing ESI source. Rhodamine dyes were employed as temperature indicators using ratiometric intensity-based fluorescence techniques. The results were compared to lifetime-based techniques using tris(2,2'-bipyridyl)dichlororuthenium(II) hexahydrate, [Ru(bpy)3](2+). Both methods gave similar profiles. Nevertheless, the precision and sensitivity were higher for lifetime-based techniques in comparison to intensity-based techniques. Global warming (with ΔT ∼10 K) of the ESI plume is reported while the size of the droplet decreases along the plume. The global warming indicates that the conductive thermal transfer (between the superheated sheath gas and the solvent) is predominant and stronger than the cooling effect due to the evaporation of the droplets, and this outcome is effectively reproduced by a diffusion-controlled evaporation model. Thermal gradient focusing ESI sources therefore appear to be efficient sources for evaporating large amounts of solvent, along with an increase in temperature.
authors.affiliation: †Institut Lumière Matière, UMR5306 Université Claude Bernard Lyon1-CNRS, Université de Lyon, 69622 CEDEX Villeurbanne, France.
authors.forename: Antonin
authors.initials: A
authors.lastname: Soleilhac
authors.affiliation: †Institut Lumière Matière, UMR5306 Université Claude Bernard Lyon1-CNRS, Université de Lyon, 69622 CEDEX Villeurbanne, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Dagany
authors.affiliation: †Institut Lumière Matière, UMR5306 Université Claude Bernard Lyon1-CNRS, Université de Lyon, 69622 CEDEX Villeurbanne, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Dugourd
authors.affiliation: ‡Institut des Sciences Analytiques, UMR 5280 CNRS Université Lyon1, Université de Lyon, 69622 CEDEX Villeurbanne, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Girod
authors.affiliation: †Institut Lumière Matière, UMR5306 Université Claude Bernard Lyon1-CNRS, Université de Lyon, 69622 CEDEX Villeurbanne, France.
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Antoine