Current status and future direction for examining engineered nanoparticles in natural systems

Abstract

Environmental context. The detection and characterisation of engineered nanomaterials in the environment is essential for exposure and risk assessment for this emerging class of materials. However, the ubiquitous presence of naturally occurring nanomaterials presents a unique challenge for the accurate determination of engineered nanomaterials in environmental matrices. New techniques and methodologies are being developed to overcome some of these issues by taking advantage of subtle differences in the elemental and isotopic ratios within these nanomaterials.Abstract. The increasing manufacture and implementation of engineered nanomaterials (ENMs) will continue to lead to the release of these materials into the environment. Reliably assessing the environmental exposure risk of ENMs will depend highly on the ability to quantify and characterise these materials in environmental samples. However, performing these measurements is obstructed by the complexity of environmental sample matrices, physiochemical processes altering the state of the ENM and the high background of naturally occurring nanoparticles (NNPs), which may be similar in size, shape and composition to their engineered analogues. Current analytical techniques can be implemented to overcome some of these obstacles, but the ubiquity of NNPs presents a unique challenge requiring the exploitation of properties that discriminate engineered and natural nanomaterials. To this end, new techniques are being developed that take advantage of the nature of ENMs to discern them from naturally occurring analogues. This paper reviews the current techniques utilised in the detection and characterisation of ENMs in environmental samples as well as discusses promising new approaches to overcome the high backgrounds of NNPs. Despite their occurrence in the atmosphere and soil, this review will be limited to a discussion of aqueous-based samples containing ENMs, as this environment will serve as a principal medium for the environmental dispersion of ENMs.

Regulatory ecotoxicity testing of nanomaterials – proposed modifications of OECD test guidelines based on laboratory experience with silver and titanium dioxide nanoparticles

“…A comprehensive characterization of the NMs is necessary to interpret the results. This topic is also addressed in various papers (Laborda et al, 2016;Montaño et al, 2014;OECD, 2012) and should be performed using the latest techniques, and at least following the recommendations in the OECD WPMN document (OECD, 2012). With the present compilation of recommended modifications to ecotoxicological test guidelines, elaborated in the scope of the EU-project MARINA, the further standardization of test guidelines for the testing of NMs shall be supported.…”

Single Particle ICP-MS: Advances toward routine analysis of nanomaterials

“…It was some years between the publication of these papers and the renewed interest in spICP-MS as a stand-alone method for characterizing NPs [26] and as a powerful means to further characterize size fractionated NPs [27]. The continual and rapid increase in the use of nanomaterials and the environmental health and safety concerns regarding implementation of nanotechnology have contributed to the significant increase in interest in this approach to complement other available techniques [28,29]. It is not the purpose of this article to review all the work performed since the publication of a 2014 review article by Laborda et al [30].…”

Detection, characterization and quantification of inorganic engineered nanomaterials: A review of techniques and methodological approaches for the analysis of complex samples

“…The underlying principle is that natural NPs contain significant amounts of other elements, which is not the case for synthetic ones. Ti/Al and Ce/La ratios have been used for identification of engineered TiO 2 and CeO 2 nanoparticles by analysing bulk samples [217], as well as in combination with AF4-ICP-MS and SP-ICP-MS [102]. In any case, these techniques just provide evidence of the presence of one or more elements associated to nanoparticles and not the exact nature of such nanoparticles.…”

“…Besides, DLS techniques require information on viscosity and refractive index, which is often not available or difficult to know in samples that are highly complex. Direct coupling to size separation techniques, like FFF and HDC, may overcome polydispersity problems and the presence of interfering particles, by presenting narrow size fractions to the DLS detector [102], and it will be discussed in section 6. Although DLS has serious limitations for sizing nanoparticle suspensions in complex matrices, it is very valuable to monitor aggregation behaviours.…”