# Evolution of the Solvent Polarity in an Electrospray Plume

Author(s) Wang, Rui, Zenobi, Renato
Publication Type Journal Items, Publication Status: Published
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Title Evolution of the Solvent Polarity in an Electrospray Plume
Author(s) Wang, Rui
Zenobi, Renato
Journal or Series Title Journal of the American Society for Mass Spectrometry
Volume Number 21
Issue Number 3
Start Page 378
End Page 385
ISSN 1044-0305
Publisher Elsevier Science
Publication Place New York
Publication Date 2010
Abstract Solvent polarity plays an important role in electrospray ionization-mass spectrometry (ESI-MS), one of the most widely used analytical methods for biochemistry. To have a comprehensive understanding of how solvent polarity affects ESI-MS measurements, we systematically investigated the polarity change in the ESI plume formed from an ethanol solution using laser-induced fluorescence (LIF) spectroscopy. Two solvatochromic dyes (i.e., dyes whose fluorescence emission is sensitive to solvent polarity), Nile red and DCM (4-dicyanomethylene-2-methyl-6-p-dimethylaminostyry1-4H-pyran), were used as probes. The peak emission wavelengths of these two dyes exhibited significant red shifts (8-12 nm) when the measuring spot was moved away from the spray tip and in radial direction in the plume, indicating a dramatic polarity change during shrinking of the droplets. The emission intensities were also measured with a polarity-insensitive dye as a reference. The results are consistent with the peak wavelength measurements. Two key mechanisms responsible for the change of solvent polarity in the plume were considered, water entrainment from the surrounding air and solvent evaporation. Furthermore, quantitative analysis of the solvent polarity change was performed by using the Lippert-Mataga polarity parameter Delta f. The value of Delta f reached 0.305-0.307 at the periphery of the ESI plume, which means that the solvent polarity in the smaller droplet is close to that of a mixture of 30% water and 70% ethanol (Delta f = 0.307), even though the bulk solvent was ethanol containing less than 1% water as an impurity.
DOI 10.1016/j.jasms.2009.10.022
Additional Notes Received 17 April 2009, Revised 30 September 2009, Accepted 30 October 2009, Available online 6 November 2009
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03430
Organisational Unit(s)
NEBIS System Number 000541631
Source Database ID WOS-000276121100006
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@article{Wng2010,
author = "Wang, Rui and Zenobi, Renato",
title = "{E}volution of the {S}olvent {P}olarity in an {E}lectrospray {P}lume",
journal = "Journal of the American Society for Mass Spectrometry",
year = 2010,
volume = "21",
number = "3",
pages = "378--385",
}


E-Citations record created: Tue, 20 Apr 2010, 09:03:57 CET