Gas-phase ion–molecule reactions for resolution of atomic isobars: AMS and ICP-MS perspectives

Ion–molecule reactions that can be used for resolution of spectral overlaps of long-lived or stable (T1/2 > 100 years) atomic isobars on the long-lived radio-isotopes (100 < T1/2 < 1012 years) in mass spectrometry are considered. Results for the separations of isobaric overlaps via cation reactions with NO, N2O, O2, CO2, C2H2, CH3F studied with the Inductively Coupled Plasma Dynamic Reaction Cell™ Mass Spectrometer (ICP-DRC™-MS) with use of stable isotopes are presented. Overview of potential and reported reactions for separation of 35 isobars is given. Potential for the following isobaric pairs separation is shown (reaction gas and the extent of separation achieved to date in parenthesis): 32Si+/32S+(NO, 5 × 104), 40K+/40Ar+(N2O, 1.9 × 103), 40K+/40Ca+(N2O, 50), 59Ni+/59Co+(N2O, 6), 79Se+/79Br+(O2, 7.2 × 103), 81Kr+/81Br+(C2H2, 1.5 × 104), 93Mo+/93Nb+(N2O, 100), 93Mo+/93Zr+(N2O, 150), 135Cs+/135Ba+(N2O, 8 × 104), 137,138La+/137,138Ba+(O2, 40), 146Sm+/146Nd+(CO2, 1.5 × 105), 176Lu+/176Hf+(NO, 2.8 × 103), 187Re+/187Os+(N2O, 2.8 × 104). Effect of instrumental parameters on reactivity is discussed. The relevance of this work to accelerator mass spectrometry is discussed briefly.