Internal Energy Distribution in Electrospray Ionization from the Multiple-Collision Model: The case of a Thermal-Like Distribution

Rondeau, David and Drahos, László and Vékey, Károly (2014) Internal Energy Distribution in Electrospray Ionization from the Multiple-Collision Model: The case of a Thermal-Like Distribution. RAPID COMMUNICATIONS IN MASS SPECTROMETRY, 25 (11). pp. 1273-1284. ISSN 0951-4198 (Unpublished)

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Abstract

In the presented study, the ion survival yields of the theoretical mass spectra simulated by the MassKinetic software are fitted with the experimental ion survival yield of substituted benzylpyridinium cations reported in a precedent paper (J. Mass Spectrom. 1999, 34, 1373-1379). A partially elastic multiple collision model is considered for describing the ion behaviour into the desolation area of the ESI source. The adjusting parameters are not the shape and the position of the P(Eint) curve but rather parameters related to the source acting, such as the pressure and the kinetic energy of ions entering the desolvation zone. In the case of a PE SCIEX ESI source interfaced with a quadrupole mass spectrometer, the energy uptake can then be well-defined by considering the case of a thermal-like distribution an average number of “effective” collisions of 29. From this model, it’s possible to correlate the voltage values applied on the orifice of the desolvation area to initial kinetic energy of ions entering into the collision zone of the ESI source. In the present case, these theoretical initial kinetic energy values range from 5.5 to 9 eV and the results of calculations shown also that the mean internal energy <Eint> increases linearly with the orifice voltage. This modelling allows defining the internal energy distribution of ions in different part of the ESI source. The activation conditions occurring into the studied ESI source can be compared to a warm-up of ions. Indeed, the internal energy distributions resemble to thermal distribution of ions having a “characteristic temperature” (Tchar) parameter between 1020 to 1550 K. In addition, this study evidences a linear correlation between <Eint> and Tchar. The slope value of this curve can be related to a calorimetric parameter such as the heat capacity of the activated substituted benzytlpyridinium cations.

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