March 2017 - Characterisation of nanomaterials

The Consortium members have been extensively discussing methodologies as well as their in-house/externally generated data, but concluded that method optimisation work (both on sample preparation and particle size distribution) is needed to allow the establishment of recommended methods for different types of nanomaterials represented within the Consortium. Such work is scheduled for 2017. Before finalisation of this method optimisation work, the Consortium will not recommend any specific methodology.

As soon as the method optimisation work is finalised, the Consortium will release a communication on this topic.

For an overview and discussion of the available methodologies for the determination of primary particle size distribution, secondary particle size distribution (aggregates, agglomerates), and volume specific surface area, we refer to the following documents:

• JRC reports (2011, 2012, 2014, 2015);
• The recent reply of the JRC to a comment on the application of the VSSA concept (potential issues with e.g. polydisperse/porous materials) (see Gibson et al., 2016, as an answer to Lecloux, 2015);
• A publication from Wohlleben et al., 2013 (BASF) in which ZrO2 samples are characterised together with many other materials.

Additionally, we would like to highlight a publication* on the use of VSSA to characterize nanomaterials. This is an important outcome of the EU NanoDefine project, in which several materials have been characterized. A correlation has been found between the volume specific surface area (VSSA) and the median diameter (D50) on a number basis as derived from electron microscopy. The results of this work have been translated into a paper which has just been accepted for publication in the Journal of Nanoparticle Research. This will most likely allow to make some clarifications regarding VSSA during the public consultation on the recommended definition of nanomaterials.

Moreover, we have been informed that the JRC is supposed to provide guidance on methodologies for characterizing nanomaterials by the end of 2017.

* Wohlleben et al. (2017), Reliable nanomaterial classification of powders using the volume-specific surface area method, J Nanopart Res (2017) 19:61.