Common use of Background of the task Clause in Contracts

Background of the task. TEM analyses can play an important role in the implementation of the newly established regulatory framework of the European Commission (EC) regulating the use of nanomaterials in consumer products [2-8]. TEM is one of the few techniques that can identify nanoparticles according to the current definitions. If particles can be brought on an electron microscopy (EM) grid and if their distribution is homogeneous and representative for the sample, the combination of transmission electron microscopy (TEM) imaging with image analysis is one of the few methods that allow obtaining number-based distributions of the particle size and shape, describing the sample quantitatively [9-11]. EM further is a well suited technique because of its resolution covering the size range from 1 nm to 100 nm specified in various definitions of NM [12], and its ability to visualize colloidal nanomaterials as well as primary particles in aggregates in two dimensions. Disadvantages of EM analysis of nanomaterials include the bias from suboptimal sampling and sample preparation, the estimation of properties of 3D objects from 2D projections, the interpretation of the size of primary particles in aggregates or agglomerates, the relatively high number of particles required for measurement, and the need to develop algorithms for automated image analysis for each separate type of nanomaterial. In many cases, technical solutions that can overcome these disadvantages are available or under development, e.g. more advanced EM techniques such as electron tomography and cryo-EM can be used to obtain information about the 3rd dimension of the particles and to avoid artefacts [13-17]. A review discussing the different steps required for the physical characterization of nanomaterials in dispersion by transmission electron microscopy in a regulatory framework is given by ▇▇▇▇ et al. [18]. The implementation of the EC-definition of a nanomaterial [4] across various regulatory fields requires a detailed detection and characterization of manufactured nanomaterials by appropriate, validated testing methods [19, 20]. In this deliverable, SOPs for quantitative TEM analysis in the context of the EC definition are proposed and applied and validated on a series of nanomaterials, by intra-laboratory and inter-laboratory validation based on the estimation of the measurement uncertainties and by interpretation of the obtained results with alternative methods. These include ensemble techniques based on light scattering, such as dynamic light scattering (DLS) and particle tracking analysis (PTA), and single particle inductively coupled plasma-mass spectrometry (SP-ICP-MS) [1].