Investigation of the electrospray plume by laser-induced fluorescence spectroscopy

Laser-induced fluorescence spectroscopy has been employed to probe the electrospray plume through measurement of the emission spectra of fluorescent dyes in the spray stream. The system is evaluated with respect to sensitivity and reproducibility using solutions of Eosin Y under typical electrospray conditions. Application of the technique for monitoring spray-induced pH changes is demonstrated using fluorescence signals from a pH-sensitive fluorophore, carboxyseminaphthorhodafluor-1 (C.SNARF-1). To our knowledge, this is the first direct measurement of pH within the electrospray plume.