Nanotechnologies make use of the properties of nanomaterials. Characterising the properties of nanomaterials, and their structure at the nanoscale (1 nm to 100 nm), requires advanced measurement methods. These methods are often complex or new. Certified reference materials are the much needed tools to monitor the performance of these methods and to help laboratories develop confidence in their measurement results.
The JRC's Institute for Reference Materials and Measurements (IRMM) produces a wide range of certified reference materials; an exhaustive list can be retrieved via the online catalogue for reference materials. Recently released reference nanomaterials include nanoparticle materials with certified average particle sizes.
Characterisation of nanoparticles
Nanoparticles (particles with an external size smaller than 100 nm) are used in many applications, such as paints, coatings, electronics, cosmetics and food. Reliable measurements of the properties of nanoparticles are crucial to develop new products, but also to determine whether specific nanomaterials pose a risk to health and the environment, or not. To support the laboratories measuring and testing nanoparticles, IRMM develops certified nanoparticle reference materials based on relevant industrially produced particles.
An example is ERM-FD100, which was released in 2011 and which is a colloidal silica certified for its particle diameter according to four different particle size analysis methods. Indicative values were assigned for additional measurement methods. A second colloidal silica certified material was released in 2012 and work on multimodal nanoparticle materials and on elongated nanoparticles is ongoing. IRMM also has an
ISO 17025 laboratory accreditation
for the characterisation of parameters characterising the size distribution of nanoparticle materials. The laboratory supports the development of the mentioned nanoparticle reference materials by testing the homogeneity and stability of the candidate reference materials and by participating in the interlaboratory studies that are used to determine the to-be-certified property values.
Development and standardisation of new measurement methods
The certification of reference materials critically depends on the availability of reliable measurement methods. In a relatively young scientific area such as nanotechnology, many new methods are being developed and proposed for use, also in the regulatory context. IRMM, in support of its main customers (the EC policy services), is therefore permanently evaluating the relevance and reliability of proposed measurement methods. In a
JRC reference report
, candidate measurement methods for implementation of the EC Recommendation on the definition of nanomaterial are investigated.
Some of these method evaluations are done through participation in third-party funded projects. For these studies, IRMM develops (non-certified) reference materials or representative test materials, e.g. where the nanoparticles are embedded in complex 'matrices' such as food (Nanolyse) or biological fluids (NanoChOp). The users of these materials are not provided with certified values, but the materials are sufficiently homogeneous and stable for the purpose of these dedicated studies and thereby contribute to the efforts towards the validation of the methods.
If a new method has been validated and found relevant, then IRMM can support its standardisation in the corresponding ISO and CEN committees (ISO/TC 229, ISO/TC 24, CEN/TC 352). For an agreed and standardised measurement method, IRMM can produce the required certified reference material. For example, on request of industry, IRMM is currently collaborating with ISO/TC 24 and the US National Institute for Standards and Technology to develop a nanoparticle reference material with a certified zeta-potential value. (Zeta-potential is a parameter related to the surface charge of suspended particles and it helps predict the tendency of the nanoparticles to agglomerate and stick together.)