Detect and measure nanos – Nanometrology

Detect and measure nanos – Nanometrology

By AVICENN Team – last modified March 2023

Detect and measure nanomaterials, what for?

To comply with the law

Importers, producers and users of nanomaterials need to characterize their nanomaterials, by establishing a kind of identity card specifying their physico-chemical parameters in order to correctly complete theobligation declaration of substances with nanoparticle status and the European obligations (registration in REACH et labeling for cosmetics, biocidal products and food).

To better identify nanomaterials and take the necessary precautionary measures

Today, there are still too few 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 on the toxicity and ecotoxicity of these nanomaterials is still incomplete, the acquisition of a better knowledge of these exposures is essential to better ensure the protection of the environment and human health.

To provide, complete, specify and/or verify this information, companies, laboratories and health or environmental agencies need tools and methods for the 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 the human body.

Different techniques available, to be crossed for better reliability

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

• analytical methods and tools are now available to monitor the presence of nanomaterials in the air¹On controlling the presence of nanomaterials in the air, see Assess and monitor nanoparticle emissions in the workplace,veillenanos.fr and, with regard to the emission of nanoparticles in the environment, see in particular
  - Interim report – elements relating to the metrological monitoring in the environment of titanium dioxide nanoparticles (TiO2) and the examination of the feasibility, HCSP, October 2019 (publication June 2020
  - Estimation of the average annual concentrations in the air around an industrial site producing substances in the nanoparticle state – Cristal – Thann site, titanium dioxide production unit, INERIS, October 2017
  - Monitoring guide in the air around classified facilities – Fallout of atmospheric emissions – Impact of human activities on the environment and health, INERIS, November 2016.
• progress has also been made on detection in surface waters.

Large margins for improvement still exist²See – 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 at academic and industrial level).

Multiple parameters to take into account to characterize nanos

To assess the emerging risks related to the dissemination 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 better identification of materials manufactured at the nanometric scale and better physico-chemical characterization (ISO /TR 13014:2012). 

However, the detection of nanomaterials at low concentrations in soils and complex environments (food products, cosmetics, etc.) remains delicate and requires the use of expensive tools and different and complementary methods, because no technique allows alone to apprehend in their entirety all the parameters of characterization of nanoparticles. It is necessary to combine different analysis techniques – one of them being electron microscopy; the choice of techniques to be adopted is made according to the information one wishes to obtain and the cost and/or time constraints to be taken into account.

What are the existing techniques?

There are direct and indirect techniques for measuring the dimensional properties of particles. Electron microscopy is the most efficient technique for accessing the shape of particles, which 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 the fact that there are relatively few spherical nanoparticles.

Harmonization and intercalibration of measurement methods, deemed necessary for several years³See
- Nanomaterials: A review of definitions, applications and health effects. How to implement safe development, Eric Gaffet, Physical Reports, Volume 12, number 7, pages 648-658, September 2011
- Safety of Nanomaterials, Exposure Reduction State of the art and developments, François Tardif, presentation at the day “Views on nanotechnology: challenges, debates, perspectives”, Institute for Risk Management, October 18, 2011
- To see Requirements on measurements for the implementation of the European Commission definition of the term “nanomaterial, Joint Research Center (JRC), 2012 (see the summary in French on the website ofEurosdo Or that of NanoNorma)is in progress. Research work now makes it possible to use these more efficient tools and should allow further significant progress in the years to come, as well as harmonization (at least at European level).

Sample preparation

For manufactured and industrial products, the sampling step is a key step in order not to distort the measurements. It requires specialized expertise.

Detection of nanomaterials in living organisms

Even more delicate, the detection of nanomaterials in living organisms is also the subject of research and notable progress.⁴See 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 to enable better identification and characterization of nano-objects? 

• In December 2019, the Joint European Research Center (JRC) published a investigation report to help companies determine if their materials are nanomaterials.
• In February 2020, ANSES in turn finalized a investigation report very important, carried out with the support of the LNE in particular: this "Review of the analytical methods available for the characterization of nano-objects" aims to avoid erroneous classification and deficient risk analyzes due to unsuitable analytical approaches and anticipate the revision of the definition recommendation of the term “nanomaterial” by the European Commission.
• In May 2020, the work of the Club nanoMétrologie was published: the inter-comparison aimed at evaluating the practices of different French players to characterize the size distribution of nanoparticles using the SMPS technique⁵See An 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) shows that the SMPS technique, mainly used to characterize the granulometry of particles in the aerosol phase (air quality & professional exposure to nanoparticles), makes it possible to properly characterize the distribution of nanoparticles in colloidal solution over a range sizes ranging from a few nanometers up to about 500 nm after an aerosolization step. It is considered very interesting by the LNE, given its sensitivity, its resolution and the accessible size range.
• In mid-June 2021, the European Food Safety Agency (EFSA) published a report on the physico-chemical characterization of nanoparticles in food additives. Produced with Sciensano & the support of the Joint Research Center (JRC), it presents tests carried out by transmission electron microscopy (TEM) and (sp)ICP-MS.
• In 2022, a " NanoMesureFrance center was born in France, supported by the LNE.
• Le 14th December 2022, the DGCCRF published the Methodological note relating to the analysis of nanoparticles and the characterization of nanomaterials present in consumer products prepared by the Joint Laboratory Service (SCL).
• On February 23, 2023, NanoMesureFrance published a “ Reaction to the methodological note of the SCL » summarizing the main information contained in the SCL note and listing the possible actions, within NanoMesureFrance, in order to contribute to a better identification of nanomaterials.

To be continued ...

Focus: Detection and characterization of nanomaterial residues in water

It is difficult to detect nanoparticles in low concentration water today⁶See 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.
Due to their small size and especially their strong reactivity, nanomaterials tend to interact with almost all the elements present in water, according to highly variable configurations depending on their physico-chemical characteristics and the composition of the environment: they can therefore undergo transformations in the aquatic environment.

French researchers whom we have contacted deplore the lack of funding for the research work that would be necessary: ​​according to them, in the absence of specific regulations, there is no particular pressure to develop innovative techniques for detecting nanoparticles in the water.

Progress is nevertheless underway thanks to advanced research and tools in this area.⁷See in particular:
- Sewage spills are a major source of titanium dioxide engineered (nano)-particle release into the environment, Loosli F et al., About. Science: Nano, 6, 763-777, 2019
– The Nancy hydrology laboratory (NHL) of the National Health Security Agency (ANSES) acquired equipment to measure nanoparticles in water in order to carry out analyzes from 2015.
- The intervention Jérome Rose (CEREGE) at the Synchrotron Soleil in March 2018 ; in short, the measurements call upon numerous techniques in combination of tools (the CEREGE uses 7 different tools): X-rays come to the rescue of electron microscopy. It is also necessary to study the interactions with the matrix of the nanoparticles. 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, n°31, May 2017
- Detection and quantification of nanomaterials in natural waters using 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), speech 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
- Slideshow presentation of the Aquanano program by Hélène Pauwels: "AQUANANO, Transfer of manufactured nanoparticles in aquifers: development of a methodology and identification of processes" to ANR J3N in November 2011: The Aquanano program has given rise 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.