Analysis of benzannelated thiophene derivatives by negative-ion chemical ionization using oxygen as a reagent gas

Article abstract of DOI:10.1002/jms.1190300615

Under the conditions of negative-ion chemical ionization with O₂ as a reagent gas [NCI(O₂)], thiophene derivatives suffer surface-catalysed oxidative degradation with subsequent ionization of the resulting species. These degradation reactions are to some extent structure specific and thus may be used for the localization of rings and/or substituents. It is advisable, however, to combine NCI(O₂) with either electron impact ionization or positive ion CI. The latter ionization methods yield abundant M^+. ions but hardly any structure-specific fragments, whereas with NCI(O₂) the determination of the molecular mass may be difficult owing to the competing oxidation reactions.