Design of instrumentation for probing changes in electrospray droplets via the Stern-Volmer relationship
by Ham, Jason Earl; Durham, Bill; Scott, Jill R.
Electrospray ionization (ESI) is a proven method for introducing large intact molecules into the gas phase. However, the processes that occur within this ion source are poorly understood. We have developed instrumentation and methodology to probe the evolution of droplets within the electrospray plume. Using emission lifetime spectroscopy, excited-state lifetimes of [Ru(bpy)(3)](2+) with and without a known quencher, 2,3,5,6-tetramethyl-p-phenlyenediamine, present were observed. Lifetimes were shown to decrease as quencher concentration increased, as expected. Rate constants (with and without quencher present) were determined and correlated with quencher concentration using the Stern-Volmer relationship. Stern-Volmer plots reveal the linearity of the quenching reaction and can be used to determine the concentrations of species within the electrosprayed droplets. The evolution of the ESI droplets can be probed by comparing the concentration of a species at different locations within the plume. (C) 2005 American Institute of Physics.
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