Efficient polyatomic interference reduction in plasma-source mass spectrometryvia collision induced dissociation

Abstract

Evidence is provided that illustrates quadrupole ion traps can be used to selectively attenuate strongly bound diatomic ions occurring at the same nominal mass as an analyte ion of interest. Dissociation rates for TaO⁺ (D₀ ∼ 750 kJ mol⁻¹) are found to be at least an order of magnitude larger than the loss rate of Au⁺ due to scattering under “slow heating” resonance excitation conditions at q_z = 0.67 and using neon as the bath gas. This rate difference is sufficient for the selective removal of this strongly-bound diatomic ion over the loss of the Au⁺ at the same mass-to-charge ratio. Other examples of quadrupole ion trap CID for the selective reduction of common plasma-generated species are also evaluated by examining the dissociation of GdO⁺ in the presence of Yb⁺, and Cu₂⁺ in the presence of Te⁺. In each case, a different method of applying the excitation signals is presented, and the attenuation rates for the diatomic species due to CID are substantially larger than scattering losses for the bare metal ions. Evidence is also presented that demonstrates CID can be accomplished in concert with a slow mass analysis scan, thereby providing a means of (1) eliminating polyatomic ions (formed in the plasma or reaction cell) over an extended mass range, (2) recovering metal ion signal from the metal-containing polyatomic ions, and (3) minimizing deleterious secondary reactions of product ions.