Gas-Phase Ion-Molecule Interactions in a Collision Reaction Cell with ICP-MS/MS: Investigations with CO₂ as the Reaction Gas

Carbon dioxide (CO₂) was used as a reaction gas to investigate the gas-phase ion-molecule interactions using the Agilent 8900 ICP-MS/MS. A solution containing forty-five elements representative of the periodic table was used to supply the ions to react with CO₂ in the collision/reaction cell (CRC). The only significant product ions formed were monoxides. The general reactivity was shown to be consistent with density functional theory (DFT)-predicted reaction enthalpies, such that all predicted exothermic reactions produced product ions at levels of at least 1% of the unreacted ion. Most endothermic reactions observed had sufficient kinetic energy in excess of the reaction enthalpies. Our results suggest that reaction enthalpy is a reasonable predictor of reactivity with CO₂ on the timescales of the interactions in non-thermal ICP-MS/MS systems. The ease and rapidity of data collection with the ICP-MS/MS and DFT calculations using the NWChem suite has value given the scarcity of thermochemical data of CO₂ reactions in the literature. These studies are especially useful for the identification of targeted reaction chemistries to be leveraged for analytical method development, such as for the inline separation of isobaric interferences from analytes of interest.