Thermal decomposition and atmospheric pressure chemical ionization of alanine using ion mobility spectrometry and computational study.

This study investigates the impact of thermal decomposition on the ion mobility spectrum of L-alanine using ion mobility spectrometry (IMS) and computational methods. By employing a post-injection delay system, we examined the evolution of ion peaks corresponding to thermal decomposition products and their interaction with protonated alanine. Experimental results revealed that the observed ion mobility spectra predominantly feature protonated isomers and adduct ions. Computational analysis using Density Functional Theory (DFT) predicted the thermodynamically favored structures and stabilities of these products. Findings indicate that protonation at the nitrogen site in alanine is more stable than at the oxygen site, and observed peaks correspond to protonated isomers and adducts formed with ammonium ions. Further investigations showed that thermal decomposition of alanine generates ammonia, contributing to the formation of new adduct ions. This research provides new insights into the behavior of amino acids under thermal conditions with implications for analytical chemistry and biochemistry.