Basic Information
Abstract Number: 890-3    
Author Name: Evan R Williams Affiliation: University of California, Berkeley
Session Title: Pittsburgh Analytical Chemistry Award - WEBCASTING
Event Type: Award
Event Title: Electrochemistry and Photochemistry in Mass Spectrometry
Presider(s): Jackovitz, John Start Time: 09:20 AM ( Slot # 5 )
Date: Tuesday, March 13th, 2012 Location: 300
Keywords: Electrochemistry, Electrospray, Mass Spectrometry, Molecular Spectroscopy

Abstract Content
One of the most recognized of all scientific formulas is Einstein’s relationship between energy and mass: E = mc2. By precisely measuring mass differences between ions, Prichard and co-workers showed that Einstein’s famous relationship is good to at least 0.00004% [1]. Extending such high precision measurements to measuring the masses of much lower energy UV-Vis photons would require significant improvements in instrumentation. An alternate method, which can be used to determine the energy of a photon directly from a mass measurement, is to use ion nanocalorimetry [2]. Absorption of UV or visible photons by hydrated ions that are stored in, and temperature equilibrated with, the ion cell of a Fourier-transform ion cyclotron resonance mass spectrometer results in sequential water molecule loss from the charged nanodrop. The absorbed photon energy is deduced from the number of water molecules lost from the nanodrop, or if the ion fluoresces, the energy of the emitted photon is determined from the product masses. This method for measuring ion fluorescence has the important advantage that all dissociation products resulting from emission are observed irrespective of the direction in which the photon is emitted, i.e., this is equivalent to 100% photon collection efficiency, which makes this indirect method for measuring fluorescence in the gas phase highly sensitive. Calibration of the nanocalorimetry method using photons of known energy makes it possible to obtain accurate thermochemical data for a variety of different physical processes. In combination with electron capture, accurate absolute electrochemical half-cell redox potentials can be obtained without using any theory or models making it possible for the first time to obtain an absolute electrochemical scale entirely from experimental data alone.
1. Rainville, S., et al. Nature 2005, 438, 1096-1097.
2. Donald, W. A., et al. J. Am. Chem. Soc. 2010, 132, 6904-6905.