Engineered nanomaterials (NM) play a crucial role in achieving sustainable development goals and in transitioning broad range of industries including from health, personal care and food to more sustainable economy. Robust methods for NM number concentration determination are not only needed to support development of more effective and safer products, but very important to comply with regulatory testing requirements [1,2]. In this vein, the EU recommendation for the definition of NM (2011/696/EU, revised in June 2022) for regulatory purpose clearly describes the need for determination of the percent content of nanoscale particles within the consumer product or additive, i.e. the particle number concentration (PNC).

To this end, single particle inductively coupled plasma mass spectrometry (spICP-MS) has been recognised by the international scientific community as a robust and popular method for number-based quantification of NMs which, following validation through several international interlaboratory comparisons, has reached the level of maturity permitting standardisation (i.e. ISO/TS 19590:2024). However, in order to obtain reliable PNC data with spICP-MS the instrument’s transport efficiency (TE) must be determined accurately [3]. Several different approaches for TE determination have been proposed so far [ISO/TS 19590:2024], mostly reliant on reference materials, which are of limited availability. The Dynamic Mass Flow (DMF) method has been recently proposed as a powerful approach for TE determination. Using DMF under specified optimal operating set up and conditions [4], direct traceability to the SI unit of kg is achievable, without the need for calibration with reference materials.

This lecture will demonstrate the potential of DMF for SI traceable PNC characterisation of selected types of NMs and method’s performance validated through participation in several international laboratory comparisons. Application to value assignment of PNC to much needed reference materials will also be discussed. Finally, feasibility of the DMF method to obtain accurate PNC under operating ranges and set ups outside of the published recommendations [4] but that still comply with key method requirements is investigated. They include temperature, flow rate and sample introduction system, as well as the instrument types.

References

[1] European Commission Regulation. No. 1223/2009, of 30 November 2009 on Cosmetic Products. 2009. http://data.europa.eu/eli/reg/2009/1223/oj

[2] European Commission. Guidance on the safety assessment of nanomaterials in cosmetics. 2020. https://data.europa.eu/doi/10.2875/40446

[3] H.E. Pace, N.J. Rogers, C. Jarolimek, V.A. Coleman, C.P. Higgings, J.F. Ranville. Anal. Chem., 2011, 83, 9351-9369.

[4] S. Cuello-Nuñez, I. Abad- Álvaro, D. Bartczak, M.E. del Castillo-Busto, D.A. Ramsay, F. Pellegrino, H. Goenaga-Infante. J. Anal. At. Spectrom., 2020, 35, 1832-1839.