analysis of nanoparticlesNanoparticles have existed since the dawn of time, but the term nanoparticle has only been coined fairly recently, having emerged in the 1990s. When studies of these particles began in the mid-1970s, they were referred to as ultra-fine particles (see Granqvist and Buhrman). The International Organization for Standardization (ISO) defines nanoparticles as particles that have at least one dimension (i.e. length, width or diameter) which is between 1 and 100 nanometers in size. They come in a variety of shapes, including spheres, nanotubes, nanowires, quantum dots and fullerenes.

 

 Natural Nanoparticles in the Environment

Nanoparticles exist naturally in the environment, in, for example volcanic ash, smoke from forest fires, clouds and ocean spray. They are also found in car exhaust and cigarette smoke. As far back as the 9thcentury, nanoparticles were unknowingly used by artists to generate a glittering effect on the surface of earthenware pots. These artisans discovered that by applying a thin film of metallic salts on the surface of previously glazed pots and then heating the pot again in a kiln in a reducing atmosphere, the salt ions migrated to the outer surface where they were reduced back to the metal. The metal atoms then agglomerated into nanoparticles which caused the light scattering, glittery effect.

 

Engineered Nanomaterials

With the high prevalence of such particles in the natural world, you might well ask what all the worry is about. Well, with the advent of nanotechnology in the early 1980s, an increasing amount of so-called engineered nanomaterials (ENMs) that have novel physical, thermal, optical and biological properties have been created. Today, there are a myriad of ENMs being manufactured for a wide range of medical, cosmetic, environmental and energy applications (see UnderstandingNano.com).

Perhaps the most well-known application of nanoparticles is in sunscreen formulations, (link to article) where the absorption and light scattering properties of ZnO and TiO2 particles are put to good use preventing harmful UV radiation from reaching the skin. ENMs are of concern as it has been identified that, as particle size decreases, some metal-based nanoparticles in particular (e.g. Ag, Au, and Cu particles) show increased toxicity compared to the same material in bulk form. In addition, nanoparticles have been shown in laboratory studies to interact with components inside mammalian cells, initiating inflammatory responses and causing destruction of mitochondria, leading to apoptosis (programmed cell death) or necrosis (un-programmed cell death).

Inevitably, a proportion of ENMs end up in our water supplies and food. This has sparked concern about the possible toxicity of some of these materials to humans and now there are moves to introduce legislation relating to the production, use, and disposal of such materials.

 

Nanotechnology and Regulations on the Horizon

In the U.S. the United States National Nanotechnology Initiative (NNI) is the coordinating agency for all U.S. federal efforts on nanotechnology. There is currently no U.S. legislation specific to nanomaterials, with decisions regarding them being left to existing authorities such as the U.S. EPA and the U.S. FDA. The U.S. EPA has adopted a case-by-case approach to evaluating submissions of nanoscale materials under the U.S. EPA Toxic Substances and Control Act (TSCA). In 2006, the FDA set up the Nanotechnology Task Force which has since generated a series of guidelines regarding the safety of nanoparticles in cosmetics, food and animal feedstuffs. The FDA also has a series of ongoing nanotechnology programs covering additional areas including drugs, biological agents and radiological applications.

In Europe, the European Commission generated a report in 2005 on Nanosciences and nanotechnologies: An action plan for Europe 2005-2009, which included a section on public health, safety, environmental and consumer protection. This was followed in 2011 by a Commission Recommendation on the definition of nanomaterial (2011/696/EU) in which specific terms and meanings relating to nanomaterials were detailed. In the UK, the Health and Safety Executive have responded to these recommendations by adding nano-specific modifications to the Registration, Evaluation, Authorisation and restriction of CHemicals (REACH) regulations.

In addition to the above, more general documents, the EU has developed specific guidelines regarding nanoparticles in food (REGULATION (EU) No 1169/2011) and cosmetics (REGULATION (EC) No 1223/2009 Article 16) and is now in the process of developing nanoparticle reference materials. This leads us neatly to the subject of how you go about measuring nanoparticles.

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 Measuring Nanoparticles

How you tackle nanoparticle measurement depends on what you mean by the term measure. If you are interested in the size of the particles, you have several techniques available to you including electron microscopy, dynamic light scattering (DLS), centrifugal liquid sedimentation (CLS), field flow fractionation (FFF) and X-ray diffraction (XRD) to name a few. If however you are interested in both the size and the composition of the nanoparticles, then you’ll need techniques such as scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), near infra-red (NIR) and single particle inductively coupled plasma mass spectrometry (spICP-MS). And, if you are particularly interested in metal and metal oxide nanoparticles, such as Au, Ag and TiO2 particles, you can still use NIR, SEM-EDX or spICP-MS, but if you actually want to quantify the nanoparticles as well, that leaves you with spICP-MS.

Most of you will probably be familiar with ICP-MS, but might be wondering how spICP-MS differs to the standard analysis approach. Basically, spICP-MS is a kind of homeopathic analysis method, in which you dilute your samples by very large factors so that you can detect individual particles as they fly through the plasma. All that’s required is a sensitive, fast scanning quadrupole ICP-MS with high signal to background and either some instrument software or a suitable spreadsheet to process the data to provide nanoparticle size, composition and concentration information. If you’d like to learn more about the application and capabilities of spICP-MS, there’s an informative on-demand webinar by nanoparticle guru Jörg Bettmer from the University of Oviedo that you can watch at your leisure. (You will need to register to play the webinar.)

We, as a company, are heavily involved with programs focused on developing methods for reliable and routine nanoparticle measurement, and we are proud to announce our partnership with the NanoDefine project. NanoDefine is a consortium of 29 European research, technology and development (RTD) performers, metrology institutes and nanomaterials / instrument manufacturers, whose goal is to develop an integrated analytical approach to implement the European Commission definition of nanomaterial (2011/696/EU), as described earlier in this blog).

 

ICP-MS Characterization of Nanoparticles

To specifically learn more about how our ICP-MS solution (Thermo Scientific iCAP Q ICP-MS can help you characterize and quantify metal and metal oxide nanoparticles in your samples, take a look at the following resources on nanoparticle detection in food samples and the NanoLyse project:

By the way, we will also be presenting solutions and technologies for spICP-MS at the forthcoming 10th International Conference on the Environmental Effects of Nanoparticles and Nanomaterials in the historic city of Vienna, Austria, in Sept 2015.

 

Additional Resources

  • The Nanotechnology Industries Association (NIA) is a voice for the industrial nanotechnologies supply chains, and is a good source of legislative and other information relating to nanoparticles.
  • Nano and Me is a site for anyone interested in nanotechnologies, produced by Hilary Sutcliffe, the Director of the Responsible Nano Forum. It is particularly useful for consumer groups wanting to know more about the safety of nano products and small businesses learning about regulation.
  • Interest in nanoparticle analysis has increased steadily in the last few years, as uses of engineered nanoparticles in particular are proliferating and their behavior and potential negative effects on the environment and human health are not yet well understood. See this video to learn more.
  • To view an interactive PDF compendium of application notes for ICP-MS nanoparticles analysis, click here.

 

If you need to characterize and quantify nanoparticles in your samples, we would very much like to hear from you. Enter your questions on methods, workflows or products using Comments box below.