ac500132j_si_001.pdf (402.74 kB)
Gas-Phase Ions Produced by Freezing Water or Methanol for Analysis Using Mass Spectrometry
journal contribution
posted on 2014-08-05, 00:00 authored by Vincent
S. Pagnotti, Shubhashis Chakrabarty, Beixi Wang, Sarah Trimpin, Charles N. McEwenIntroducing
water or methanol containing a low concentration of
volatile or nonvolatile analyte into an inlet tube cooled with dry
ice linking atmospheric pressure and the first vacuum stage of a mass
spectrometer produces gas-phase ions even of small proteins that can
be detected by mass spectrometry. Collision-induced dissociation experiments
conducted in the first vacuum region of the mass spectrometer suggest
analyte ions being protected by a solvent cage. The charges may be
produced by processes similar to those proposed for charge separation
under freezing conditions in thunderclouds. By this process, the surface
of an ice pellet is charged positive and the interior negative so
that removal of surface results in charge separation. A reversal of
surface charge is expected for a heated droplet surface, and this
is observed by heating rather than cooling the inlet tube. These observations
are consistent with charged supercooled droplets or ice particles
as intermediates in the production of analyte ions under freezing
conditions.