Characterisation of gas cell reactions for 70+ elements using N 2 O for ICP tandem mass spectrometry measurements.

One widely utilised method to reduce spectral interferences for measurements using inductively coupled plasma mass spectrometry (ICP-MS) is to employ the use of a reaction cell gas. Nitrous oxide (N 2 O) is a highly reactive gas typically used for mass-shifting only target analytes to a higher mass-to-charge ratio with increased sensitivity ( e.g. +16, +32, +48 amu for monoxide, dioxide, and trioxide product ions respectively). Traditionally, the use of N 2 O was limited to selected applications due to the creation of new interferences that also interfere with the detected masses of interest. However, with the advent of inductively coupled plasma tandem mass spectrometry (ICP-MS/MS), the use of N 2 O has gained more traction, with a growing number of publications in recent years. Here, a comprehensive study of the use of N 2 O for the determination of 73 elements has been conducted, with a comparison to the most widely used mass-shift method using oxygen (O 2 ) as a reaction gas. In total, 59 elements showed improved sensitivity when performing mass-shift with N 2 O compared to O 2 , with 8 elements showing no reaction with either gas. Additionally, N 2 O demonstrated a collisional focusing effect for 36 elements when measuring on-mass. This effect was not observed using O 2 . Monitoring asymmetric charge transfer reactions with N 2 O highlighted 14 elements, primarily non-metals and semi-metals, that enter the gas cell as metastable ions and could be used as an alternative mass-shift option. The results from this study highlight the high versatility of N 2 O as a reaction cell gas for routine ICP-MS/MS measurements.