A mechanism study of positive ionization processes in flowing atmospheric-pressure afterglow (FAPA) ambient ion source with controlled plasma and ambient conditions

Interpretation of Ionization Mechanism Responsible for Reagent Ion and Analyte Formation in Microwave-Induced Plasma Desorption Ionization Mass Spectrometry

“…Protonated molecular ions [M + H] + are the most common analyte ions being observed in mass spectrometer, indicated the dominant reaction pathway is the proton-transfer reaction, and the protonated water clusters are the major reagent ions involved in the reaction. H 3 O + ions are the important precursor ions responsible for the protonated water-cluster formation . Many plasma-generated high energic particles have significant contributions to the generation of H 3 O + , for instance, the discharged noble species (e.g., Ar + , IE = 15.8 eV), , the atmospheric charge-transfer reagent ions (e.g., O 2 + , NO + ), ,− and the free radical substances (e.g., OH*, O*), , ultimately leading to the formation of protonated water clusters ions.…”

“…For example, the PA of H 2 O, (H 2 O) 2 , and (H 2 O) 3 is 691, 831, and 941 kJ/mol, respectively. For most samples applied in mass spectrometry analysis, their PA below 1000 kJ/mol. , Therefore, clusters ions with high order are not conducive to sample ionization, more attention is focused on acquiring abundant of clusters ions with low order even the hydronium ions H 3 O + participated in sample ionization, , which could be well feedbacked through mass spectrometer. Anyhow, this study monitored the yield of PWCs ions though the intensity of m / z 37, further confirmed the optimal distance for reagent ions production.…”

“…Furthermore, atmospheric oxygen was considered a vital factor in soft ionization . In our previous studies, it was concluded that nitrogen and oxygen show different capacities in the signal intensity of protonated water clusters ions and or protonated analytes . It was worth noting that, although there were distinct differences in discharge regime (e.g., MIPDI, MPT source in microwave regime and DART, LTP, FAPA sources in glow regime) and geometry of these plasma-based ADI sources, the effect of the source operating conditions on ionization characteristics exhibits some similar attributes.…”

The Electrospray (ESI) and Flowing Atmosphere-Pressure Afterglow (FAPA) Mass Spectrometry Studies of Nitrophenols (Plant Growth Stimulants) Removed Using Strong Base-Functionalized Materials

“…Oxygen, nitrogen, water, and analytes, in contact with the high-energy helium atom He (2 3 S), played key roles in chemical and physical formation of ions in FAPA ionization. The production of N 2 + , O 2 + , NO + , and ions of analytes in this process resulted from the interactions between air and water molecules with He (2 3 S) [ 29 ]. In negative ion mode, ions were produced by the interaction of thermal electrons in the afterglow region with ambient oxygen.…”

Evaluation of a modified halo flowing atmospheric pressure afterglow ion source for the analysis of directly injected volatile organic compounds

“…In FAPA sources, plasma-generated species (ions and excited species of the He plasma gas, such as He 2 + , He metastable, and He 2 ,) depart into the open atmosphere and then interact with the ambient species to create reagent ions 9 This reactive region is known as the afterglow and it is used to thermally desorb and ionize samples through, mainly, proton transfer and/or charge transfer mechanisms 10 . FAPA-MS coupling was evaluated for several applications such as screening of counterfeit electronic components 11 , quantitative analysis of thin-layer chromatography plates 12 , analysis of metal complexes 13 , rapid screening of pesticides in food 14 , analysis of designer drugs 15 or the determination of ambient organic aerosols in real time 16 .…”