title: Rapid profiling of laser-induced photochemistry in single microdroplets using mass spectrometry.
abstract: Rapid assessment of laser-induced photochemistry in single microdroplets is afforded by on-demand microdroplet generation coupled to a commercial ion-trap mass spectrometer. Single microdroplets (diameter ∼50 μm, 65 pL) fall on a steel needle held at +2 kV where they subsequently form a spray that is directed toward the inlet of an ion-trap mass spectrometer. It is demonstrated that single microdroplet mass spectra are recordable, one at a time, for methanol droplets containing 100 μM 4-iodoaniline. Extending on this, to probe laser-initiated photochemistry in single picoliter volumes, a UV laser pulse is timed to intercept the droplet before hitting the needle. Comparison of laser-on and laser-off mass spectra reveals the laser-initiated photochemical products. We demonstrate the technique by following UV laser initiated chemistry in methanol droplets containing 4-iodoaniline and 3-(iodomethyl)-N,N,N-trimethylbenzenamine and reveal numerous products within a few hundred single droplet experiments over several minutes. This technique allows for rapid detection of laser-initiated photochemistry in single picoliter volumes.
authors.affiliation: School of Chemistry, University of Wollongong , Wollongong, New South Wales 2522, Australia.
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Tracey
authors.forename: Bartholomew S
authors.initials: BS
authors.lastname: Vaughn
authors.forename: Brendon J
authors.initials: BJ
authors.lastname: Roberts
authors.forename: Berwyck L J
authors.initials: BL
authors.lastname: Poad
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Trevitt
mesh_terms: D007834:Lasers; D013058:Mass Spectrometry / Q000379:methods*; D010777:Photochemistry; D015203:Reproducibility of Results