Study on Temperature-Responsive Characteristics of Reactant Ions in Corona Discharge Ion Mobility Spectrometry

Abstract

Ion mobility spectrometry (IMS) is an analytical technique and can separate gas-phase ions under atmospheric pressure conditions. Using a laboratory-build direct-current positive corona discharge ion mobility spectrometry (CD-IMS), this study investigates the relationship between reactant ions and temperature when environmental air is used as the buffer gas. Quantum chemical calculations are employed to support experimental observations, such as the initial intensities of ion peaks and their variations with temperature, thereby elucidating the mechanisms underlying temperature-responsive behavior of reactant ions. Experimental results indicate that the hydrated cluster ions NH₄⁺(H₂O)ₙ, NO⁺(H₂O)ₙ, H₃O⁺(H₂O)ₙ, and O₂⁺(H₂O)ₙ exhibit distinct responses to temperature variations due to processes such as dehydration and transformation into hydronium ions upon reaching certain hydration numbers. Specifically, NH₄⁺(H₂O)ₙ and NO⁺(H₂O)ₙ disappear when the temperature rises to 383 K, while O₂⁺(H₂O)ₙ disappear at 413 K. In contrast, H₃O⁺(H₂O)ₙ persists throughout the temperature range and displays a trend of initial decrease followed by a continuous increase in intensity. Additionally, the drift time of NH₄⁺(H₂O)ₙ, H₃O⁺(H₂O)ₙ, and O₂⁺(H₂O)ₙ generally decrease with rising temperature, whereas NO⁺(H₂O)ₙ shows a slight increase.