PIKAL Petr Precheza a.s.

Particle size measurement method which can completely fulfill EU nanomaterial definition is technically impossible due to fundamental problems in this definition. There are two main sources of problems –understanding nature of primary particles and emphasis on number based distribution. There is no particle size measuring method which can distinguish between primary particles and agglomerates without ambiguity. Common are ensemble methods which usually measure aggregates as single particles and cannot provide directly number size distribution. Particle counting method also count aggregates as single particles. Even with electron microscopy it can be difficult to clearly distinguish between aggregates and primary particles. Possible improvements of this definition are to use number size definition only after screening with well established ensemble methods and consider aggregates which cannot be dispersed to its constituent parts under reasonably severe conditions (intractable aggregates) as primary particles.