CONTROL OF FRAGMENTATION PRODUCTS FOR THE MASS-SPECTROMETRIC ANALYSIS OF POLYMERIC MIXTURES

The concept of controlled fragmentation for the analyses of mixtures is developed in the fast atom bombardment/Fourier transform mass spectrometry of a new oligomeric class of cyclic beta-keto lactones. These cyclic oligomers produce fragments during ionization with masses that are identical to smaller homologues. By using the proper alkali metal ion, dissociation reactions are limited to loss of the metal ions. In this way, fragments do not interfere with the identification of quasimolecular ions. From competition experiments involving several alkali metals, Cs+ was identified as the best candidate to analyze mixtures. It enhances the quasimolecular ion signal but does not produce Cs+ coordinated fragments. The metal was then used to analyze a reaction mixture to elucidate the oligomerization mechanism.