Gas-phase ion mobility of protonated aldehydes in helium measured using a selected ion flow-drift tube

0585947 - ÚFCH JH 2025 RIV US eng J - Journal Article
Omezzine Gnioua, Maroua - Španěl, Patrik - Spesyvyi, Anatolii
Gas-phase ion mobility of protonated aldehydes in helium measured using a selected ion flow-drift tube.
Rapid Communications in Mass Spectrometry. Roč. 38, č. 14 (2024), č. článku e9767. ISSN 0951-4198. E-ISSN 1097-0231
R&D Projects: GA ČR(CZ) GA21-25486S
Institutional support: RVO:61388955
Keywords : chemical ionization mass spectrometry * molecule reactions * SIFDT-MS
OECD category: Physical chemistry
Impact factor: 2, year: 2022
Method of publishing: Open access

Rationale
In soft chemical ionization mass spectrometry, analyte ions are produced via ion–molecule reactions in the reactor. When an electric field E is imposed, the ion drift velocity vd determines the reaction time and the effective ion temperature. Agreement between experimental ion mobilities and theoretical predictions confirms the accuracy of the ion residence time measurement procedure.
Methods
A selected ion flow-drift tube (SIFDT), an instrument with a chemical ionization source, was used to produce protonated aldehydes and selectively inject them into the resistive glass drift tube filled with He. Arrival-time distributions of ions were obtained using the Hadamard modulation. Reduced ion mobilities were then obtained at a pressure of 2 hPa in the E/N range of 5–15 Td. Theoretical ion mobility values were calculated using two methods: hard-sphere approximation and trajectory modelling.
Results
The measured mobilities of three saturated and three unsaturated protonated aldehydes do not show substantial variation across the studied E/N range. Effective temperatures calculated using the Wannier formula from measured gas temperatures ranged from 300 to 315 K. Experimentally obtained values of the near-zero- E/N-reduced ion mobilities agree with both methods of calculations typically within ±3% standard deviation (maximum ±5%).
Conclusions
The experimental SIFDT values of reduced mobilities in He of protonated aldehyde molecules generated from a chemical ionization source are in close agreement with two different theoretical methods based on the density functional theory calculations of ion geometries and partial atomic charges. Besides its fundamental importance, the ion mobility results validate the correct operation of the drift tube reactor and the ion residence time measurement procedure. Diffusion losses can also be determined from these results.

Permanent Link: https://hdl.handle.net/11104/0353581