# Metal Ion Isotope Ratio Using ESI-Orbitrap HRMS: Proof of Concept and Initial Performance Evaluation for Lead Isotopic Ratios

## TL;DR

This paper introduces a new method using high-resolution mass spectrometry to measure metal isotope ratios, with a focus on lead, offering high accuracy and precision.

## Contribution

The novel approach uses electrospray ionization and Orbitrap HRMS for metal isotope ratio analysis, achieving high selectivity and comparable precision to ICP-MS.

## Key findings

- The method successfully determined lead isotope ratios with high accuracy.
- Mass bias correction methods improved accuracy even with matrix components.
- Precision is comparable to single-collector ICP-MS.

## Abstract

This study introduces
a novel approach using an electrospray source
coupled to an Orbitrap MS instrument to determine metal isotope ratios.
The procedure involves forming a complex between the ion of interest
and an appropriate ligand, generating gas-phase ions via electrospray
ionization, selecting the complex mass by quadrupole filtering, and
performing collisional fragmentation to yield free metal ions. The
isotopic pattern of the free ion is then analyzed by high-resolution
MS. The approach ensures high selectivity and interference-free spectra.
A proof-of-concept study was conducted to determine Pb isotope ratios,
focusing on identifying the factors that influence the accuracy and
precision of the procedure. At this early stage, optimal accuracy
was achieved even in the presence of matrix components by applying
mass bias correction methods originally developed for other isotope
ratio techniques; precision is comparable to that achieved by single-collector
ICP-MS instrumentation. This approach may complement conventional
methods that suffer from limited mass resolution and usually require
extensive sample preparation.