Detecting and measuring nanos – Nanometrology

Detecting and measuring nanos – Nanometrology

By the AVICENN team – last modification in March 2023

Why detect and measure nanomaterials?

To comply with the law

Importers, producers and users of nanomaterials need to characterize their nanomaterials, establishing a sort of identity card specifying their physicochemical parameters in order to correctly fulfill the obligatory declaration of substances in nanoparticulate form and the European obligations (registration in REACH and labeling for cosmetics, biocides and food).

To better identify nanomaterials and take the necessary precautionary measures

There are still too little reliable data on the quantities and types of manufactured nanomaterials – or residues of these nanomaterials – released into the environment or in the workplace and to which ecosystems and human populations are exposed. Insofar as knowledge of the toxicity and ecotoxicity of these nanomaterials is still incomplete, acquiring a better understanding of these exposures is essential to better protect the environment and human health.

To provide, complete, clarify and/or verify this information, companies, laboratories and health or environmental agencies need tools and methods for detection, identification, quantification and monitoring of nanomaterials in different environments (air, water, soil, food, various objects), as well as in living organisms – and more particularly in the human body.

Different techniques available, to be combined for a better reliability

Until recently, there was a consensus on the lack of reliable (and affordable) nanometrology instruments and tools as well as a lack of shared methods. Things are changing: nanometrology has made great progress in terms of instrumentation and protocols:

• methods and analytical tools are now proposed to monitor the presence of nanomaterials in the air¹On the control of the presence of nanomaterials in the air, see Evaluating and monitoring nanoparticle emissions in the workplace, veillenanos.fr and, regarding nanoparticle emissions in the environment, see
  – Interim report – elements for environmental metrological monitoring of titanium dioxide (TiO2) nanoparticles and feasibility review, HCSP, October 2019 (publication June 2020
  – Estimation of average annual concentrations in the air around an industrial site producing substances in the nanoparticulate state – Cristal site – Thann, Titanium dioxide production unit, INERIS, October 2017
  – Guide de surveillance dans l’air autour des installations classées – Retombées des émissions atmosphériques – Impact des activités humaines sur les milieux et la santé, INERIS, November 2016.
• progress has also been made in the detection in surface water.

There is still a lot to do²Cf. – Quality of physicochemical data on nanomaterials: an assessment of data completeness and variability, Comandella D et al, Nanoscale, 7, February 2020 to improve them and have them adopted and respected by the entire scientific community (both academic and industrial).

Multiple parameters to take into account to characterize nanos

In order to assess the emerging risks associated with the release of nano-objects in commercial products and in the environment, it is necessary to know how to identify them. In 2012, ISO/TC 229, the technical committee in charge of nanomaterials for international standardization (ISO), proposed a list of parameters aimed at a better identification of nanoscale manufactured materials and a better physicochemical characterization (ISO/TR 13014:2012).

The detection of nanomaterials at low concentrations in soils and complex environments (food products, cosmetics, etc.) is still delicate and requires the use of expensive tools and various complementary methods, as no single technique can provide a complete understanding of all the parameters for characterizing nanoparticles. It is necessary to combine different analysis techniques – one of them being electron microscopy. The choice of the techniques to be used depends on the information that one wishes to obtain and any cost and/or time constraints.

What are the existing techniques?

There are direct and indirect techniques to measure the dimensional properties of particles. Electron microscopy is the most powerful technique to identify the shape of particles. This makes it the most “versatile” technique (able to characterize a very wide variety of substances in terms of shape, size, chemical compound), which is very important considering that there are relatively few spherical nanoparticles.

Considered necessary for several years, work on harmonizing and intercalibrating the measurement methods³See
– Nanomaterials: A review of definitions, applications and health effects. How to implement a secure development, Eric Gaffet, Comptes Rendus Physique, Volume 12, number 7, pages 648-658, September 2011
– Safety of Nanomaterials, Reduction of Exposure State of the art and developments, François Tardif, presentation at the day “Regards sur les nanotechnologies : enjeux, débats, perspectives”, Institut de Maîtrise des Risques, October 18, 2011
– See Requirements on measurements for the implementation of the European Commission definition of the term “nanomaterial, Joint Research Center (JRC), 2012 (see the French summary on the Eurosfaire website or the NanoNorma website)is now underway. Research work is now making these tools more effective and should lead to further significant progress as well as to harmonization (at least at the European level) in the years to come.

Sample preparation

For manufactured and industrial products, the sampling step is a key step to avoid distorting the measurements. It requires a high level of expertise.

The detection of nanomaterials in living organisms

Even more delicate, the detection of nanomaterials in living organisms is also the subject of research and notable progress⁴See for example: An analytical workflow for dynamic characterization and quantification of metal-bearing nanomaterials in biological matrices, Monikh FA et al, Nature protocols, 2022.

What initiatives exist to enable better identification and characterization of nano-objects?

• In December 2019, the European Joint Research Center (JRC) published a report to help companies determine if their materials are nanomaterials.
• In February 2020, ANSES finalized a very important report, with the help of LNE. This “Review of available analytical methods for the characterization of nano-objects” aims to avoid misclassification and deficient risk analysis due to inappropriate analytical approaches and to anticipate the revision of the definition recommendation of the term “nanomaterial” by the European Commission.
• In May 2020, the work of the NanoMetrology Club was published: the inter-comparison aimed at evaluating the practices of different French stakeholders to characterize the size distribution of nanoparticles via the SMPS technique⁵An intercomparison exercise of good laboratory practices for nano-aerosol size measurements by mobility spectrometers, Gaie-Levrel F et al (LNE), Journal of Nanoparticle Research, 22 : 103, 2020 (Electric Mobility Spectrometer). This shows that the SMPS technique, mainly used to characterize the granulometry of particles in aerosol phase (air quality & occupational exposure to nanoparticles), allows to successfully characterize the distribution of nanoparticles in colloidal solution on a size range going from a few nanometers up to about 500 nm after an aerosolization step. This is considered as very interesting by LNE, given its sensitivity, resolution and accessible size range.
• In mid-June 2021, the European Food Safety Agency (EFSA) published a report on the physicochemical characterization of nanoparticles in food additives. Produced with Sciensano & the support of the Joint Research Center (JRC), it presents tests conducted by transmission electron microscopy (TEM) and (sp)ICP-MS.
• In 2022, a “NanoMesureFrance center” was created in France, supported by LNE.
• On December 14, 2022, the DGCCRF published the Note méthodologique relative à l’analyse des nanoparticules et à la caractérisation des nanomatériaux présents dans des produits de consommation (Methodological note on the analysis of nanoparticles and the characterization of nanomaterials present in consumer products) written by the Service commun des laboratoires (SCL).
• On February 23, 2023, NanoMesureFrance published a “Reaction to the SCL’s methodological note” summarizing the main information contained in the SCL’s note and listing possible actions, within NanoMesureFrance, to contribute to a better identification of nanomaterials.

To be continued…

Zoom: Detection and characterization of nanomaterial residues in water

It is difficult today to detect nanoparticles in water at low concentrations ⁶Cf. von der Kammer, F et al, Analysis of engineered nanomaterials in complex matrices (environment and biota): general considerations and conceptual case studies, About. Toxicol. Chem., 31, 32e49, 2012.
Because of their small size and especially their strong reactivity, nanomaterials tend to interact with almost all the elements present in water, according to very variable configurations depending on their physicochemical characteristics and the composition of the medium: they can therefore undergo transformations in the aquatic environment.

French researchers we contacted deplore the lack of funding for the research work that should be necessary: they stated that, in the absence of specific regulations, there is no particular pressure to develop innovative techniques for detecting nanoparticles in water.

Progress is nevertheless being made thanks to the advancement of research and tools in this field⁷See in particular:
– Sewage spills are a major source of titanium dioxide engineered (nano)-particle release into the environment, Loosli F et al, Environ. Sci.: Nano, 6, 763-777, 2019
– The Nancy hydrology laboratory(LHN) of the French National Health Security Agency(ANSES) has acquired equipment to measure nanoparticles in water in order to conduct analyses starting in 2015.
– The intervention Jérome Rose (CEREGE) at the Synchrotron Soleil in March 2018; in short, the measurements use many techniques in combination of tools (CEREGE uses 7 different tools): X-rays come to the rescue of electron microscopy. Interactions with the nanoparticle matrix must also be studied. The Synchrotron, on the basis of preliminary measurements, makes it possible to characterize nanoparticles in complex media.
– Detection of manufactured nanoparticles in drinking water and food additives, Sivry Y, ANSES Scientific Watch Bulletin, No. 31, May 2017
– Detection and quantification of nanomaterials in natural waters by an integrated multi-tool approach, Karine Phalyvong, IPGP, November 2016
– The world’s first model for engineered nanoparticles in surface waters, Wageningen UR, June 3, 2015
– Characterization and detection of nanomaterials in surface waters, Wilkinson K et al. (University of Montreal), presentation at the 83rd Acfas Congress, Colloquium 210 – Presence, persistence, fate and effects of nanomaterials in the environment, May 2015
– A simple and sensitive biosensor for rapid detection of nanoparticles in water, Journal of Nanoparticle Research, 16:2253, January 2014
– Slide show presentation of the Aquanano program by Hélène Pauwels: “AQUANANO, Transfer of manufactured nanoparticles in aquifers: development of a methodology and identification of the processes” to J3N of the ANR November 2011: The Aquanano program has led to advances in the determination of nanoparticles in water, based on the use of devices for chemical and isotopic analysis (method for screening the presence of C60 in natural waters).
– Bibliographic overview of techniques for characterizing nanoparticles in water , M Blessing, JP Ghestem (BRGM), 2011.