PNNL

Abstract

Nitrous oxide (N2O) was used as a reaction gas to investigate the gas phase ion-molecule interactions using the Agilent 8900 QQQ-ICP-MS. A multi-element standard containing 45 elements with masses ranging from 9 to 208 u was measured in the presence and absence of N2O. The main product ion species observed were oxides and nitrides. Comparison of the N2O reaction results with similar measurements conducted with O2 revealed that N2O was more effective at forming oxides in general: the elements Cd and Pb were shown to produce oxides with N2O where the reaction did not occur with O2. Nitrous oxide was also shown to produce a significant amount of nitride species in a few cases. The general reactivity was shown to be consistent with DFT-derived reaction enthalpies, such that all exothermic reactions produced product ions at levels at least 1% of the unreacted ion. Of the reactions where the octopole bias was -14V, there existed an energy threshold of 2.4 eV, such that reactions with ?Hrxn > 2.4 eV were not observed. Similarly, the reaction threshold where the octopole bias was -18 V was 4.1 eV. The relationship between the octopole bias and the threshold enthalpy demonstrates how the collision cell ion guide affects the kinetic energy of the ion beam and can control the detection of product ions. Our results suggest that reaction enthalpy is a sufficient predictor of reactivity with N2O in non-thermal ICP-MS/MS systems.