High-mass analysis using quadrupolar excitation/ion cooling in a Fourier transform mass spectrometer.

Quadrupolar axialization has been applied to matrix-assisted laser desorption/ionization Fourier transform mass spectrometric analysis of singly charged polymer and protein ions. When a quadrupolar excitation is applied in the presence of argon collision gas, ions are driven to the center of the cell, where they can traverse the conductance limit and be detected in the lower pressure analyzer cell of a dual cell instrument. It is shown that single frequency quadrupolar excitation permits highly selective detection of single oligomers of poly(ethylene glycol) 6000. Resolution enhancement is demonstrated for bovine insulin and ubiquitin, where spectra with resolving powers of 92,000 and 25,000, respectively, are obtained. Finally, quadrupolar axialization is demonstrated to be effective for molecules with masses as large as 13,000 Da.