Jens Griep-Raming et.al.: An Electrospray Ionization Source for the
Investigation of Thermally Initiated Reactions
- Author(s): Jens Griep-Raming, Juergen O. Metzger
- Title: An Electrospray Ionization Source for the Investigation of
Thermally Initiated Reactions
- Date of Upload: 2000
- Article: Anal. Chem.2000, 72,5665-5668, Department of Chemistry,
University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, 26129 Oldenburg,
Germany
- Keywords: ESI-MS, electrospray ionization, mass spectrometry, reactive
intermediate, reaction, solution, thermally initiated reactions, carbocations,
radicals, scandium
- Abstract:
- An electrospray ionization source for mass spectrometry is described, which
allows one to heat the spray capillary. Thermal dissociation of the trityl
dimer 1 and tetra(panisyl) hydrazine (3) have been investigated, operating
the ESI source as electrolytic cell to ionize neutral species, e.g. the trityl
radical 2. Electrospray ionization (ESI) mass spectrometry (MS), introduced
by Fenn et al.1 and Alexandrov et al.,2 has been shown to be useful for analysis
of various kinds of analytes. With this technique, it became possible to analyze
reaction substrates, products, and intermediates at the same time directly
from reaction solutions. There are some examples in the literature that deal
with organic reactions at room temperature,3-11 very few operating at temperatures
below room temperature,12 but we found no publications that are concerned
with the ESI investigation of reactions at elevated temperatures. As our work
has been focusing on radical reactions13 and many radical reactions can be
initiated by thermal decomposition of, for example, azo compounds or peroxides
at elevated temperatures, we developed an ESI source that allows one to heat
the reaction solution only a short time before the ionization occurs, or (even
better) to heat the ionization region, thus enabling us to detect thermally
generated reactive intermediates with very low steady-state concentration
in the reaction solution. Because radicals are neutral species and are not
ionized in the ESI process in general, we thought to operate the ESI source
as an electrolytic cell as described by Van Berkel14. Thus, the thermally generated
radicals should hopefully be oxidized electrolytically in situ to cations
that can be observed by mass spectrometry. As first examples, we have investigated
the behavior of the trityl dimer (1-diphenylmethylene-4-trityl-2,5-cyclohexadiene)
(1) and of tetra(p-anisylhydrazine (3) at different temperatures.
- URL: http://www.chemie.uni-oldenburg.de/oc/metzger/publikationen/pdf/88.pdf
(application/pdf)
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