chemical ionisation
chemical ionisation
A process of ionisation involving the reaction of a reagent ion and a neutral molecule to yield a charged ionic form of the molecule.The first step in chemical ionisation is the creation of the reagent ion by electronically ionising reagent gas molecules, which are present in great excess. A stable population of reagent ions is formed through ion–molecule reactions, which eventually react with the neutral gas-phase molecules. In a common example, methane gas is ionised to form predominantly CH5, which then reacts with the neutral sample molecule in a process of protonation to form MH.