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Jean-François Gal and Pierre-Charles Maria
Chimie des Matériaux Organiques et Métalliques,
Faculté des Sciences, Université de Nice-Sophia Antipolis, 06108 Nice Cedex 2, France
Lorenza Operti, Roberto Rabezzana* and Gian
Angelo Vaglio
Dipartimento di Chimica Generale e Organica Applicata, Università di Torino, Corso Massimo d’Azeglio 48, 10125 Torino, Italy. Email:
Roberto.Rabezzana@unito.it |
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The effects of different experimental parameters on rate constant measurements performed by mass spectrometry were investigated with a two-
level fractional factorial design. This chemometric technique allows a study of the effects of selected factors and of their interactions on the response of an experiment by
performing a limited number of analyses. The selected factors were: sample pressure, energy of the ionising electrons, reaction time and ionisation time. In this work, two mass
spectrometric techniques were compared: Fourier transform ion cyclotron resonance (FT-ICR) and quadrupole ion trap (QIT) mass spectrometries. Experimental results were
obtained from a study of a reaction system consisting of the condensation between triethylphosphite and its fragment ion
(CH3CH2O)2P+. Apparent bimolecular rate constants are clearly larger when determined by QIT than by FT-ICR, because of
collisional stabilisation of the adduct ion by helium buffer gas introduced in the QIT spectrometer. However, the QIT rate constant extrapolated to zero helium pressure is almost
identical to the FT-ICR value; this supports the conclusion regarding the buffer gas effect. Minor effects evidenced by the chemometric method were attributed to the sample
pressure and to the reaction time. |
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Keywords:
Fourier transform ion cyclotron resonance, quadrupole ion trap, chemometrics, ion/molecule reactions, kinetics |
