Single particle (sp)ICP-MS is a powerful technique to characterize nanoparticles and colloids in aqueous suspensions with respect to their size, concentration and elemental composition. However, analysing suspensions containing water reactive particles is still challenging. For instance, the main cement hydration product ‘Calcium-Silicate-Hydrate’ shows variable particle sizes and Ca/Si ratios according to the original cement/water mix and influences cement rheology to an unknown extent. To stop the hydration process and to investigate these nanoparticulate early hydration products, alcohol-based suspensions may be applied. In this work, we present for the first time a spICP-MS method developed for particle characterization in pure ethanolic suspensions. Several certified reference materials presenting variable particle sizes (10‒1000 nm), particle number concentration and elemental composition (i.e. Au, Al, Ca, Fe and Si) were investigated via spICP-MS and compared to methods such as Nanoparticle Tracking Analysis and Transmission Electron Microscopy for method validation. To minimise particle agglomeration, all suspensions were sonicated systematically in a temperature-controlled sonification bath. Ethanol induced polyatomic interferences via ICP-MS were selectively overcome via optimised gas modes (e.g., H₂, H₂+O₂, O₂ or NH₃) for each target element.
spICP-MS data post-processing was performed using an in house Python-based algorithm, capable of separating particles from the background (i.e. Gaussian or Poisson method) and assigning raw data peaks to their corresponding particle events (i.e. integration) to then calculate masses, sizes and particle number concentrations [adapted from 2, 3].
Overall, this novel spICP-MS method allows the direct quantification of water reactive phases developed for all fast nucleation or mineral formation processes. This approach expands ongoing and future research, including the study of Calcium-Silicate-Hydrate in the sorption and transport of radionuclides from deep geological nuclear waste repositories, and can readily be applied to investigate nanoparticulate calcined clays as a sustainable alternative to reduce the CO₂ footprint of Ordinary Portland Cement [1].

References
[1] S. Hellmann et al.; ACS Omega, 2024, 9, 30294–30307.
[2] T. E. Lockwood et al.; J. Anal. At. Spectrom., 2021, 36, 2536–2544.
[3] L. A. Currie et al.; Anal. Chem., 1968, 40, 586–593.