A NEW TRISECTOR TANDEM MASS-SPECTROMETER FOR NEUTRALIZATION-REIONIZATION STUDIES

A new trisector EBE mass spectrometer is modified to accommodate neutralization-reionization mass spectrometry (NRMS) experiments. The instrument is equipped with dual collision cells and an electrostatic deflector in the field-free region between B and E for the study of neutralization-reionization (NR) reactions. Combined with linked scanning, a third collision cell, situated after the ion source, can be used for the charge reversal of mass-selected cations (+ NR-) or anions (-NR+). Collisionally-activated dissociation (CAD) processes can be studied in any one of the three cells. The capabilities of the instrument are illustrated with specific problems pertaining to gas phase chemistry and mass spectral analysis: combined NR and CAD experiments are used to investigate the structures and isomerization tendencies of C2H5O+ and C4H8O+ ions, and the stabilities and reactivities of the hypervalent radicals CH2 = CHOH2. and ClHCl. and the Norrish-type II biradical .CH2CH2CH2CH.OH. It is demonstrated that detection of the neutrals eliminated in unimolecular ion dissociations significantly facilitates differentiation of molecular isomers and elucidation of peptide ion fragmentation mechanisms.