Multi-elemental Nd, Sm, Eu, Gd isotope ratio measurements by stop-flow isotachophoresis coupled to MC-ICPMS

In this study, a new analytical procedure based on isotachophoresis (ITP) coupled to a multi collector inductively coupled plasma mass spectrometer named Stop-Flow-ITP-MC-ICPMS is developed for exhaustive and high-precision multi-elemental isotopic characterization. We demonstrate that Stop-Flow-ITP makes it possible to stop the analytes migration several times for a duration compatible with the detector configuration changes without losing the separation performance. With this procedure, isotope ratio measurements of four lanthanides of interest for nuclear applications (Nd, Sm, Eu and Gd) were obtained with a reproducibility better than 0.4% in a single analysis with only 20ng of each element. A nebulization interface between ITP and MC-ICPMS composed of a dual inlet spray chamber and a multiple flow stream valve made it possible to perform isotopic reference standard injections for on-line mass bias correction by the sample standard bracketing approach. The flexibility of the Stop-Flow-ITP-MC-ICPMS procedure opens the way to online determination of isotope ratio measurements of multiple analytes present in a sample in a single analysis.