A parallelized tool to calculate the electrical mobility of charged aerosol nanoparticles and ions in the gas phase

Coots, Joshua; Gandhi, Viraj; Onakoya, Tunde; Chen, Xi; Larriba-Andaluz, Carlos

doi:10.1016/j.jaerosci.2020.105570

Cited by 24 publications

(16 citation statements)

References 18 publications

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“…Thus, we concluded that the CCS value of a small molecule is determined by its polarizability, primarily owing to the VdW interaction represented by the spatial size information embedded in the polarizability, combined with a small contribution from the dipole-dipole interaction. This nding is supported by several computational studies 18,19,20 in which compound interactions were simulated as the sum of the short-range VdW potential and long-range ioninduced dipole potential. However, these studies did not consider dipoles induced by the electric eld in the IM chamber.…”

Section: Ccs Value Of a Small Molecule Determined By Its Polarizabilitysupporting

confidence: 52%

Collision Cross Section of a Small Molecule Determined by its Polarizability rather than its Mass and Shape

Wisanpitayakorn

Sartyoungkul

Kurilung

et al. 2022

Preprint

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The rotationally averaged collision cross section (CCS), measured by ion mobility mass spectrometry (IM-MS), facilitates the identification of various types of biomolecules. Thus far, the CCS value is known to depend on the shape and size of the molecule, while other physiochemical quantities for determining the CCS values are yet to be explored. In this study, using quantum chemistry and 197 model compounds, we discovered and validated that the CCS value primarily depends on the polarizability of the molecule, a quantity representing both the spatial size and dipole-dipole interaction with buffer gas molecules. Contrary to popular belief, at a constant polarizability, a molecule’s CCS value is completely independent of its mass (m/z) and shape (ovality). The findings of this study deepened our understanding of the CCS values of small molecules, and their application will considerably improve the CCS prediction model accuracy.

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Section: Ccs Value Of a Small Molecule Determined By Its Polarizabilitysupporting

confidence: 52%

Collision Cross Section of a Small Molecule Determined by its Polarizability rather than its Mass and Shape

Wisanpitayakorn

Sartyoungkul

Kurilung

et al. 2022

Preprint

View full text Add to dashboard Cite

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“…Based upon the range of tools available to the community, the accuracy and ultimate utility of results of a computational campaign are highly dependent upon the experimental platform and the expertise of the research team. Moreover, there are ample contributions to variability in such endeavors that are linked to measurement methodology and the underlying algorithmic approach chosen. ,,,,,,, As stated previously, the predominance of ion-neutral interaction computational methods used to-date rely on either the projection approximation, trajectory method, Lennard-Jones parameters, a hybrid of the former, or a scaling factor to unify computational results in a posthoc exercise. ,,,, While surely useful within the community and necessary to refine underlying computational tools, it is analytically unsatisfying for the broader scientific community. Arguably, the degree of variation between the different computational techniques is due to the inability of routine measurement of gas-phase ion mobility to capture the role of long-range potentials for a given ion-neutral interaction.…”

Section: Discussionmentioning

confidence: 99%

“…stated previously, the predominance of ion-neutral interaction computational methods used to-date rely on either the projection approximation, trajectory method, Lennard-Jones parameters, a hybrid of the former, or a scaling factor to unify computational results in a posthoc exercise. 22,40,79,84,85 While surely useful within the community and necessary to refine underlying computational tools, it is analytically unsatisfying for the broader scientific community. Arguably, the degree of variation between the different computational techniques is due to the inability of routine measurement of gas-phase ion mobility to capture the role of long-range potentials for a given ion-neutral interaction.…”

Section: ■ Conclusion and Future Directionsmentioning

confidence: 99%

Reevaluating the Role of Polarizability in Ion Mobility Spectrometry

Naylor

Clowers

2021

J. Am. Soc. Mass Spectrom.

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With the expanding commercial availability of gasphase separation systems that incorporate gas-phase mobility, there is a concurrent rise in efforts to cast the gas-phase mobility coefficient in terms of an ion-neutral collision cross-section (CCS). The motivating factors for this trend are varied, but many aim to complement experimental results with computationally generated CCS values from in silico structural approximations. Unfortunately, the current paradigm for relating experimental mobility results to computationally derived structures relies upon empirical approaches, including a myriad of variables that do not realistically bound the comparison. In this Critical Insight, we advocate for the development of a self-consistent experimental and computational framework that uses laboratory results to constrain the scope of the modeling effort. This paper aims to prompt discussion, challenge assumptions, and promote the development of more efficient, accurate computational techniques within the gas-phase ion measurement community. Specifically, we postulate whether experimental deviations from Langevin's polarization limit (K pol ) are suitable to estimate the relative contributions of hard-sphere collisions and long-range interactions within CCS values. Not surprisingly, different molecule classes exhibit different trends in the K/K pol ratio when normalized for reduced mass, and the most common IMS calibrants (e.g., tune mix, polyalanine, tetraalkylammonium salts) follow different polarizability trends than many of the analytes probed in the literature. Succinctly, if gas-phase ion structure is largely invariant based upon the colliding neutral and newly developed experimental efforts can quantitatively capture ion polarizability, then modeling efforts describing a target analyte must be self-consistent as the collision neutral is changed in silico.

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“…In the end, we selected the lowest energy CILSs from the quantum chemical calculations and calculated their collision cross section (CCS) using Ion Mobility Software, , which models the drag force induced by the ion-neutral collisions. In the IMOS software, we used the trajectory method with Lennard–Jones potentials and quadrupole interactions included in the collisions, using the CHelpG partial charges (CHarges from electrostatic potentials using a grid-based method) calculated at the ωB97X-D/def2TZV level and listed in Section SC of the Supporting Information.…”

Section: Methodsmentioning

confidence: 99%

Molecular Origin of the Sign Preference of Ion- Induced Heterogeneous Nucleation in a Complex Ionic Liquid–Diethylene Glycol System

et al. 2020

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Heterogeneous nucleation on charged seeds has been shown to frequently prefer a given sign of electrical charge (anion or cation), at constant seed size and (apparent) chemical composition. For some systems, this sign preference can be readily understood in terms of individual chemical interactions. However, experiments are in general unable to provide satisfying molecular-level explanations for the sign preference of chemically complex systems. Here, we experimentally demonstrate a positive sign preference for charged ionic liquid seeds (CILS) with diethylene glycol vapor (DEG) and explain the physicochemical origins of this preference via quantum chemical calculations. The computational results show that all enthalpies and free energies for adsorption of DEG onto the CILS clusters are lower for the positively charged seeds compared to those for the negatively charged seeds. The main reason for this difference is the stronger hydrogen bonds in the cationic clusters originating from the ability of imidazolium-based cations to act as hydrogen bond acceptors.

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A parallelized tool to calculate the electrical mobility of charged aerosol nanoparticles and ions in the gas phase

Cited by 24 publications

References 18 publications

Collision Cross Section of a Small Molecule Determined by its Polarizability rather than its Mass and Shape

Collision Cross Section of a Small Molecule Determined by its Polarizability rather than its Mass and Shape

Reevaluating the Role of Polarizability in Ion Mobility Spectrometry

Molecular Origin of the Sign Preference of Ion- Induced Heterogeneous Nucleation in a Complex Ionic Liquid–Diethylene Glycol System

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