Novel quadrupole ion trap methods for characterizing the chemistry of gaseous macro-ions

A variety of ion manipulation techniques that have been developed to study the chemistry of gas-phase macro-ions are described and illustrated. These techniques take advantage of several unique characteristics of the quadrupole ion trap, including operation at relatively high (1 mTorr) bath gas pressure and the ability to simultaneously store positive and negative ions in overlapping regions of space. Efforts to characterize unimolecular dissociation in the ion trap via resonance excitation and thermal dissociation at elevated bath gas temperatures are described; such dissociation is of interest as a means for obtaining primary structural information and Arrhenius activation parameters for macro-ions. The use of ion/molecule chemistry to obtain composition and higher level structural information is illustrated with a description of novel HI attachment chemistry which yields information on the number and accessibility of neutral basic sites in macro-ions. Ion/ion chemistry for the manipulation of parent and product ion charge states is shown to expand the range of charge states accessible for tandem mass spectrometry (MS/MS) analysis, and to greatly simplify the interpretation of MS/MS spectra obtained from multiply charged parent ions. (C) 2000 Elsevier Science B.V.