  Current approaches to Mass Spectrometry (MS) require ionization of the
analytes of interest. For high-mass species, the resulting charge state
distribution can be complex and difficult to interpret correctly. In this
article, using a setup comprising both conventional time-of-flight MS (TOF-MS)
and Nano-Electro-Mechanical-Systems-based MS (NEMS-MS) in situ, we show
directly that NEMS-MS analysis is insensitive to charge state: the spectrum
consists of a single peak whatever the species charge state, making it
significantly clearer than existing MS analysis. In subsequent tests, all
charged particles are electrostatically removed from the beam, and unlike
TOF-MS, NEMS-MS can still measure masses. This demonstrates the possibility to
measure mass spectra for neutral particles. Thus, it is possible to envisage
MS-based studies of analytes that are incompatible with current ionization
techniques and the way is now open for the development of cutting edge system
architectures with unique analytical capability.
