Proton transfer reactions for ionized water clusters

Wróblewski, Tomasz; Ziemczonek, L.; Karwasz, Grzegorz P.

doi:10.1007/bf03166481

Cited by 15 publications

(12 citation statements)

References 23 publications

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“…However, in the presence of water, H 3 O + ions form stable water clusters via the three‐body cluster association reaction . For example, hydrated hydronium cations H 3 O + (H 2 O) n with a cluster size of n = 3 are expected to be major species in a thermally equilibrated system at ambient pressure and <1 ppm v humidity: 48

H_{3} O^{+} {({normalH}_{2} O)}_{n - 1} + H_{2} normalO + normalA ⇌ H_{3} O^{+} {({normalH}_{2} O)}_{n} + normalA .

According to previous studies, 49–51 water clusters (H 2 O) n + 1 have higher PAs than the bare water molecule H 2 O. The higher PA is the result of the added stability of H 3 O + brought about by sharing the positive charge with additional water molecules 16 .…”

Section: Ionization Pathways Resulting In the Formation Of Positive Pmentioning

confidence: 97%

Formation of positive product ions from substances with low proton affinity in high kinetic energy ion mobility spectrometry

Allers

Kirk

Schaefer

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale: Ion mobility spectrometry (IMS) instruments are typically equipped with atmospheric pressure chemical ionization (APCI) sources operated at ambient pressure. However, classical APCI-IMS suffers from a limited ionization yield for nonpolar substances with low proton affinity (PA). This is mainly due to ion clustering processes, especially those that involve water molecules, inhibiting the ionization of these substances. Methods: High Kinetic Energy (HiKE)-IMS instruments are operated at decreased pressures and high reduced electric field strengths. As most clustering reactions are inhibited under these conditions, the ionization yield for nonpolar substances with low PA in HiKE-IMS should differ from that in classical APCI-IMS. To gain first insights into the ionization capabilities and limitations of HiKE-IMS, we investigated the ionization of four model substances with low PA in HiKE-IMS using HiKE-IMS-MS as a function of the reduced electric field strength. Results: The four model substances all have proton affinities between those of H 2 O and (H 2 O) 2 but exhibit different ionization energies, dipole moments, and polarizabilities. As expected, the results show that the ionization yield for these substances differs considerably at low reduced electric field strengths due to ion cluster formation. In contrast, at high reduced electric field strengths, all substances can be ionized via charge and/or proton transfer in HiKE-IMS. Conclusions: Considering the detection of polar substances with high PAs, classical ambient pressure IMS should reach better detection limits than HiKE-IMS. However, considering the detection of nonpolar substances with low PA that are not detected, or only difficult to detect, at ambient pressure, HiKE-IMS would be beneficial. 1 | INTRODUCTION Due to their high sensitivity, fast response times, and compact design, ion mobility spectrometers are commonly used in safety and security applications such as the detection of chemical warfare agents, 1,2 toxic industrial chemicals, 3,4 drugs, 5,6 and explosives. 7-9 Basically, ion mobility spectrometry (IMS) instruments can be divided by their principle of ion separation. In this work, a drift tube (DT) ion mobility spectrometer is used. In DT-IMS, ions are separated by their motion along the axis of a drift tube driven by a homogeneous static electric field. To initiate the measurement, an ion packet is injected into the drift tube. During their motion, the ions are separated based on the absolute value of their ion mobility in the present drift gas. At the end of the drift tube, the ions are captured by a detector that converts

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H_{3} O^{+} {({normalH}_{2} O)}_{n - 1} + H_{2} normalO + normalA ⇌ H_{3} O^{+} {({normalH}_{2} O)}_{n} + normalA .

Section: Ionization Pathways Resulting In the Formation Of Positive Pmentioning

confidence: 97%

Formation of positive product ions from substances with low proton affinity in high kinetic energy ion mobility spectrometry

Allers

Kirk

Schaefer

et al. 2021

Rapid Comm Mass Spectrometry

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“…The Restricted Hatree-Fock method with 6-311G** split-valence molecular orbitals basis sets [16] with two polarization functions has been applied to geometrical optimizations and calculations of total and zero point vibrational energies for small neutral and protonated organic acids, alkanes, alcohols, methyl and ethyl acetates, acetone, and acetaldehyde. Previously [17] we applied this same methodology for dissociation and proton attachment energies for water clusters.…”

Section: Methodsmentioning

confidence: 98%

Proton affinities of simple organic compounds

2006

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The Restricted Hatree-Fock method with 6-311G** split-valence molecular orbitals basis sets has been applied to geometrical optimizations and calculations of total electronic, zero point vibrational energies and proton affinities at 298 K for small neutral and protonated alkanes, alcohols, acetic acid, methyl and ethyl acetate, acetone, and acetaldehyde. Calculated values of proton affinities are compared with experimental data.PACS : 36.40.Wa

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“…It is known that as protonated water clusters increase in size, so too does the proton affinity (PA) of the cluster [22][23][24]. The calculated PAs of the observed clusters, n = 2, 3, and 4 are 832, 888, and 919 kJ·mol -1 , respectively [23].…”

Section: Schlieren Experimental Setupmentioning

confidence: 99%

Characterization of a Direct Sample Analysis (DSA) Ambient Ionization Source

Winter

Wilhide

LaCourse

2015

J. Am. Soc. Mass Spectrom.

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Abstract. Water cluster ion intensity and distribution is affected by source conditions in direct sample analysis (DSA) ionization. Parameters investigated in this paper include source nozzle diameter, gas flow rate, and source positions relative to the mass spectrometer inlet. Schlieren photography was used to image the gas flow profile exiting the nozzle. Smaller nozzle diameters and higher flow rates produced clusters of the type [H + (H 2 O) n ] + with greater n and higher intensity than larger nozzles and lower gas flow rates. At high gas flow rates, the gas flow profile widened compared with the original nozzle diameter. At lower flow rates, the amount of expansion was reduced, which suggests that lowering the flow rate may allow for improvements in sampling spatial resolution.

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Proton transfer reactions for ionized water clusters

Cited by 15 publications

References 23 publications

Formation of positive product ions from substances with low proton affinity in high kinetic energy ion mobility spectrometry

Formation of positive product ions from substances with low proton affinity in high kinetic energy ion mobility spectrometry

Proton affinities of simple organic compounds

Characterization of a Direct Sample Analysis (DSA) Ambient Ionization Source

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