Molecule/radical reactions prior to ionization under negative chemical ionization conditions

It is shown that alkyl radical species present in CH4 or iso‐C4H10 plasma can react with substrate molecules to give [M+CnH2n] species. These species become evident especially in negative chemical ionization as [M+CnH2n]−˙ and, less obviously, in positive chemical ionization as [M+CnH2n+1]+ ions which, for example in natural products chemistry, may be mistaken for a series of homologous compounds present in the sample.