Reliability of Fourier transform-ion cyclotron resonance determinations of rate constants for ion/molecule reactions

Abstract

The results of gas-phase rate constant measurements by Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry may be influenced by the setting of instrumental parameters. The effects of pressure, ionization duration, ionization energy, selection of the parent ion, mass range, trapping potential, reaction delay and pumping-regulation-valve opening have been investigated and analysed using a two-level Plackett-Burman statistical design which is described in an appendix. This approach was tested on the ion/molecule reaction between acetyl ion and acetone: CH 3 CO + + CH 3 COCH 3 → CH 2 CO + (CH 3 COCH 3 )H + . Although space-charge effects are known to be deleterious to FT-ICR, this is the first study demonstrating, on a statistical basis, the necessity of parent ion selection for obtaining reliable rate constants. Considered independently, the other factors tested do not appear statistically significant, but the possibility of interactions among them is discussed. The mean of the rate constants from experiments with acetyl ion selection, k abs = (2.14 ± 0.18) × 10 -10 cm 3 molecule -1 s -1 , is compared with literature data.

Binding of molecular oxygen and alkenes to coordinatively unsaturated bipyridinium metal complexes in the gas phase

“…The rate coefficient was measured to be 1.9 × 10 −10 cm 3 molecule −1 s −1 , which results in a calibration factor of 1.1 by matching with the value determined by Grover et al [13] (2.14 × 10 −10 cm 3 molecule −1 s −1 ). The pressure was corrected for the relative sensitivity of the gas (calculated from the polarizability) compared to N 2 [14].…”

A kinetic study of guest displacement reactions on a host–guest complex with a photoswitchable calixarene

“…It displays a kinetic plot (including summation of all associated isotope peaks) and allows fitting to finally obtain the bimolecular rate constant and reaction efficiency20–22 from the pseudo‐first‐order rate constant and the pressure of the reactant gas in the cell. Therefore, the ion gauge was calibrated using the reaction of the acetyl cation with acetone following the procedure given by G al et al 23 For the pressure calibration, the acetyl cation was produced by the Bruker EI/CI ion source.…”

A Quadrupole Ion Trap and Fourier Transform Ion Cyclotron Resonance Concerted Study of the Kinetics of an Ion/Molecule Association Reaction: A Chemometric Approach

“…4-1 instead of 16 = 2 4 ), was created and analysed using the STATGRAPHICS plus (version 3) program (Manugistics, Rockville, MD, USA). In this case, single-factor effects only interfere with three-factor interactions (resolution IV : 4 = 1 + 3) and two-factor interactions also interact.…”

“…2,3 However, data collected with different mass spectrometric methods may exhibit large discrepancies. In two previous works utilizing chemometric techniques, 4,5 the authors have investigated the experimental factors that may affect rate constant measurements performed using Fourier transform ion cyclotron resonance (FT-ICR) 4 and quadrupole ion trap (QIT) 5 mass spectrometry instruments. The reaction studied was the following: CH 3 CO + + CH 3 COCH 3 ® (CH 3 COCH 3 )H + + CH 2 CO (1) In this simple proton transfer reaction, which is weakly exothermic, the excess energy is imparted to the products.…”

“…6 In the present work, a chemometric approach relying on experimental design techniques 7,8 was used to highlight the effect of experimental factors on the rate constant measurements performed using the two instruments. The aim of this work was to study the effect of factors, already controlled in previous studies of the reaction involving acetone, 4,5 in both FT-ICR and QIT for the phosphite association reaction which is likely to involve different limiting pathways of stabilisation depending on the pressure regime. In FT-ICR operating at low pressure, a photon emission pathway is supposed to dominate, whereas in QIT in the presence of a buffer gas, third-body collisions will dominate.…”