A double quadrupole mass spectrometer has been assembled to perform collision-induced dissociation (CID) of molecular ions sampled from a radio-frequency (rf) powered glow discharge atomization/ionization source. Low-energy ( Elab = 20 and 40 eV) collisions with argon target atoms efficiently dissociate species of the form M2+, MAr+, MO+, and Ar2+, and residual gas species. Exemplary CID mass spectra illustrate the enhanced reduction of potential molecular isobars relative to scattering losses of analyte (atomic) ions.