Isobutane and Ammonia Chemical Ionization Mass Spectrometry of Sesquiterpene Alcohols (MW 222)

Abstract

ABSTRACT The mass spectral fragmentation behavior of 21 sesquiterpene alcohols (C 15H26O; MW 222) under the conditions of chemical ionization (CI) is investigated using isobutane and ammonia, respectively, as the reagent gases. The isobutane spectra show intense fragment ions [M + H—H2O]+ for all substances. The tendency to forming further fragment ions is different for the various compounds. This behavior reveals structural characteristics to a certain degree. Only three compounds display quasimolecular ions [M + H]+with relative intensities > 10%. Therefore, isobutane is not well suited to confirm the molecular mass and classification of this compound group is not unambiguous. With ammonia a typical set of ions is formed: [M + H—H2O]+, [M + NH4—H2O]+, [M + NH4]+ and [M + NH3· NH4]+, respectively. These ions enable to confirm the molecular mass and to classify this compound group. With the use of both the reagent gases, the identity of individual substances can be confirmed by their specific ion and inte...