Investigation Of Some Thiosulfonate Derivatives By Means Of Chemical-Ionization And Tandem Mass-Spectrometry

A number of thiosulfonate derivatives have been investigated by means of ammonia chemical ionization (NH3-CI), electron impact ionization (EI) and mass-selected collision induced dissociation (CID). For most of the compounds investigated, the NH3-CI positive-ion mass spectra exhibit the addition ion, [M + NH4]+, as the dominant species, which implies that the proton affinities of the compounds investigated are less than the proton affinity of NH3. Deviation from true chemical ionization conditions resulted in efficient dissociation of the addition ion to yield substantial amounts of the protonated molecule, [M + H]+. The major fragment ions observed in the EI mass spectra and in the CID spectra indicate the cleavage of the sulfur-sulfur bond to be more efficient than other competing cleavages. This and other experimental observations are discussed.