Evaluation of the New MC-ICP-MS/MS Neoma With and Without the MS/MS Option.

In the last two years, a new generation MC-ICP-MS (Neoma) was launched by ThermoFisher Scientific and is now available in two different configurations, i.e., with and without a MS/MS option. This presentation will focus on these two settings which were installed in 2021 as a Neoma standard and upgraded to the MS/MS version in 2022. We can now compare the performances of the instrument for three different configurations, a first in the Neoma standard, a second in the Neoma upgraded but with the collision cell OFF, which should be equivalent to the first configuration, and a third in the Neoma upgraded with the collision cell ON.

First, we use the Neoma to measure precise isotopic ratios of potassium in the XHR mode and in the MS/MS configuration for which the XHR is no longer needed. The accuracy of the standard/sample bracketing method is evaluated regarding matrix tolerance to increased amount of Ca, Mg, Na, standard/sample concentration and HNO3 molarity mismatch. The d41K value of geological and biological certified reference materials are measured to assess the performance for each configuration.

Second, we use the Neoma to measure the precise radiogenic strontium isotopic ratios (87Sr/86Sr) with laser ablation and with and without the MS/MS option using SF6 in the collision cell. The 87Rb interference on 87Sr is well known and the use of an MS/MS option is a clear improvement for the determination of the accurate 87Sr/86Sr ratios. Additionally, the new Neoma have enough dispersion on the collector array to measure simultaneously, with the SF6 in the collision cell, m/z from 85Rb to 107SrF enabling the direct analysis of Rb and Sr in multicollection mode without peak jumping, allowing better precision for age evaluations.

Third, we use the Neoma to measure the isotopic ratios of selenium, copper, and iron for the three configurations. The 40Ar+36Ar, 40Ar+38Ar, and 40Ar+40Ar isobaric interferences on 76Se, 78Se, and 80Se are resolved using O2, 40Ar+23Na on 63Cu, and 40Ar+14N, 40Ar+16O on 54Fe and 56Fe using H/He. The accuracy of the standard/sample bracketing method is also evaluated with varying matrix effects and the isotopic value of geological and biological certified reference materials are proposed.