A new report by the European Commission's Joint Research Centre (JRC)
presents an in-depth review of methods available to measure the size of
nanoparticles.
Following the adoption of the definition of the term 'nanomaterial'
in October 2011, this report identifies relevant measurement methods and key
challenges for measuring nanoparticle size in the regulatory context. The report
underlines that no single measurement method can be used for all materials to
determine if each of them falls within the regulatory definition. Different methods
will be required depending on the material under investigation.
The report gives an overview of the capabilities of currently available measurement
methods, including techniques such as electron microscopy, dynamic light scattering
and centrifugal liquid sedimentation, among others. It also identifies measurement
issues that remain to be solved.
The conclusions highlight the practical challenges of measuring materials with widely
varying properties. None of the currently available methods can determine whether all
kinds of potential nanomaterials meet the regulatory definition or not. Therefore, a
proper combination of measurement methods is required. The reliabiliy of each of the
measurement methods used in such combined, tiered approaches will need to be
thoroughly checked in dedicated method validation studies.
Background information
In October 2011, the European Commission adopted Recommendation 2011/696/EU
on a common definition of the term "nanomaterial" to facilitate the regulation of
products containing such materials. The objective was twofold: to ensure their safety
and to enhance innovation and help industry.
In essence, a nanomaterial is defined as a "natural, incidental or manufactured material
containing particles, in an unbound state or as an aggregate or as an agglomerate and
where, for 50 % or more of the particles in the number size distribution, one or more
external dimensions is in the size range 1 nm-100 nm". Proper implementation of this
definition requires appropriate tools and methodologies for which measurement
aspects are crucial.
Following publications by JRC scientists in academic journals, the report is the first
comprehensive overview on the topic because it specifically assesses the suitability of
available measurement methods for implementing the European Commission's
definition.
