The question ofagglomeration and aggregation of nanoparticles is important for a wide range of issues, from product performance and associated quality control, to production process optimization, risk assessment and associated regulatory requirements.

In France, the mandatory annual declaration of nanoparticulate substances (register R-Nano) requires information on the aggregation & agglomeration state of nano-objects constituting the substance and this characteristic is one of the most complicated for declarants to fill in with primary particle size, as identified in a 2023 survey of members of the NanoMesureFrance Association.

A meeting on the subject of determining the agglomeration and aggregation state of nano-objects was organized. Tuesday April 23 with contributions from Charles Clifford (NPL / UK) which is working specifically on this subject, notably through various research projects, but also through the development of a Technical Specification at European standardization level (CEN/TC 352 Nanotechnologies).

An opportunity for the 34 participants :

• better understand the state of the art on this complex issue, for which a common definition of the terms used is key, with differences between what is considered at the level of international standardization (ISO) and the European regulatory framework,
• identify the measurands of interest to be considered and the relevant analytical techniques associated with each of them, depending on the sample form (colloidal suspension, powder, aerosol)
• to share their issues and recommendations for moving the subject forward.

It's a complex subject, and there are still a number of stages to go through before we have a simple approach that will enable us to distinguish indisputably between a Agglomeration a Aggregate !