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+C_nH_2n] species. These species become evident especially in negative chemical ionization as M+C_nH_2n]^?˙ and, less obviously, in positive chemical ionization as M+C_nH_2n+1]⁺ ions which, for example in natural products chemistry, may be mistaken for a series of homologous compounds present in the sample.