Improved proton affinity measurements for proline and modified prolines using triple quadrupole and ion trap mass spectrometers

S. Mezzache, N. Bruneleau, K. Vekey, C. Afonso, P. Karoyan, F. Fournier, J. C. Tabet

Research output: Contribution to journalArticle

14 Citations (Scopus)


Proton affinity (PA) of compounds such as proline, cis-3-methylproline, cis-3-ethylproline, cis-3-isopropylproline and cis-3-isopentanylproline was determined by kinetic method with amines as the reference bases. The effective temperatures determined using ion trap and triple quadrupole mass spectrometers were found to be significantly different. In the case of the triple quadrupole instruments, the effective temperature depends significantly on the collision energy. The influence of the apparent basicity (GBapp) on the effective temperature may be used to estimate the difference in protonation entropy (ΔΔS°) between the sample and reference compounds. In case of the ion trap mass spectrometer, the variation of the effective temperature as a function of the excitation amplitude is small, so it is difficult to account for the contribution of the entropy effects to the proton affinity value. A better estimation of the PA and ΔΔS° values for the investigated molecules is obtained by combining the GBapp and Teff data pairs that are obtained from both the mass spectrometers.

Original languageEnglish
Pages (from-to)1300-1308
Number of pages9
JournalJournal of Mass Spectrometry
Issue number10
Publication statusPublished - Oct 1 2005



  • Amino acids
  • Effective temperature
  • Entropy
  • Kinetic method
  • Proton affinity

ASJC Scopus subject areas

  • Spectroscopy

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