ChemInform Abstract: AN EXPERIMENTAL STUDY OF THE GAS‐PHASE KINETICS OF REACTIONS WITH HYDRATED HYDRONIUM(1+) IONS(N = 1‐3) AT 298 K

Böhme, Diethard K.; Mackay, G. I.; TANNER, S. D.

doi:10.1002/chin.197942139

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“…Such reactions occur in a significant number of ion sources for MS 7,8 including corona discharges, 9,10 electrospray ionization, 11−13 dielectric barrier discharges, 14,15 and soft X-rays. 16−18 One stable and reliable source at ambient pressure, the beta emitter 63 Ni, was used in early API MS instruments 1 and can be found in IMS drift tubes in use today. 19,20 The foundations for understanding gas phase ion−molecule reactions were developed and refined by the mid-1970s 21 with a broad experimental record for mass spectrometry including chemical ionization MS 22−24 and studies with ionization detectors.…”

Section: ■ Introductionmentioning

confidence: 99%

Parametric Sensitivity in a Generalized Model for Atmospheric Pressure Chemical Ionization Reactions

Lattouf

Anttalainen

Kotiaho

et al. 2021

J. Am. Soc. Mass Spectrom.

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Gas phase reactions between hydrated protons H+(H2O) n and a substance M, as seen in atmospheric pressure chemical ionization (APCI) with mass spectrometry (MS) and ion mobility spectrometry (IMS), were modeled computationally using initial amounts of [M] and [H+(H2O) n ], rate constants k 1 to form protonated monomer (MH+(H2O) x ) and k 2 to form proton bound dimer (M2H+(H2O) z ), and diffusion constants. At 1 × 1010 cm–3 (0.4 ppb) for [H+(H2O) n ] and vapor concentrations for M from 10 ppb to 10 ppm, a maximum signal was reached at 4.5 μs to 4.6 ms for MH+(H2O) x and 7.8 μs to 46 ms for M2H+(H2O) z . Maximum yield for protonated monomer for a reaction time of 1 ms was ∼40% for k 1 from 10–11 to 10–8 cm3·s–1, for k 2/k 1 = 0.8, and specific values of [M]. This model demonstrates that ion distributions could be shifted from [M2H+(H2O) z ] to [MH+(H2O) x ] using excessive levels of [H+(H2O) n ], even for [M] > 10 ppb, as commonly found in APCI MS and IMS measurements. Ion losses by collisions on surfaces were insignificant with losses of <0.5% for protonated monomer and <0.1% for proton bound dimer of dimethyl methylphosphonate (DMMP) at 5 ms. In this model, ion production in an APCI environment is treated over ranges of parameters important in mass spectrometric measurements. The models establish a foundation for detailed computations on response with mixtures of neutral substances.

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