Kinetics in DMS: Modeling Clustering and Declustering Reactions

Research output: Contribution to journalArticleResearchpeer review

Authors

  • Alexander Haack
  • W. Scott Hopkins

External Research Organisations

  • University of Waterloo
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Details

Original languageEnglish
Pages (from-to)2250-2262
Number of pages13
JournalJournal of the American Society for Mass Spectrometry
Volume33
Issue number12
Early online date4 Nov 2022
Publication statusE-pub ahead of print - 4 Nov 2022
Externally publishedYes

Abstract

Differential mobility spectrometry (DMS) uses high-frequency oscillating electrical fields to harness the differential mobility of ions for separating complex sample mixtures prior to detection. To increase the resolving power, a dynamic microsolvation environment is often created by introducing solvent vapors. Here, relatively large clusters are formed at low-field conditions which then evaporate to form smaller clusters at high-field conditions. The kinetics of these processes as the electrical field strength oscillates are not well studied. Here, we develop a computational framework to investigate how the different reactions (cluster association, cluster dissociation, and fast conformational changes) behave at different field strengths. We aim to better understand these processes, their effect on experimental outcomes, and whether DMS model accuracy is improved via incorporating their description. We find that cluster association and dissociation reactions for typical ion-solvent pairs are fast compared to the time scale of the varying separation fields usually used. However, low solvent concentration, small dipole moments, and strong ion-solvent binding can result in reaction rates small enough that a lag is observed in the ion's DMS response. This can yield differences of several volts in the compensation voltages required to correct ion trajectories for optimal transmission. We also find that the proposed kinetic approach yields generally better agreement with experiment than using a modified Boltzmann weighting scheme. Thus, this work provides insights into the chemical dynamics occurring within the DMS cell while also increasing the accuracy of dispersion plot predictions.

Keywords

    collision cross section, density functional theory, differential ion mobility, ion-solvent cluster, kinetics, reaction rates

ASJC Scopus subject areas

Cite this

Kinetics in DMS: Modeling Clustering and Declustering Reactions. / Haack, Alexander; Hopkins, W. Scott.
In: Journal of the American Society for Mass Spectrometry, Vol. 33, No. 12, 04.11.2022, p. 2250-2262.

Research output: Contribution to journalArticleResearchpeer review

Haack A, Hopkins WS. Kinetics in DMS: Modeling Clustering and Declustering Reactions. Journal of the American Society for Mass Spectrometry. 2022 Nov 4;33(12):2250-2262. Epub 2022 Nov 4. doi: 10.1021/jasms.2c00224
Haack, Alexander ; Hopkins, W. Scott. / Kinetics in DMS : Modeling Clustering and Declustering Reactions. In: Journal of the American Society for Mass Spectrometry. 2022 ; Vol. 33, No. 12. pp. 2250-2262.
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