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November 2012: On behalf of Dr. Heinz Rüdel informed Dr. Albrecht Paschke at the general meeting of the Division on September 12th, 2012 in Leipzig, among other things, that in August 2012 about 60 people were addressed by the GDCh in an info mail to become active members of the AK. In 2013 new elections for the board of directors are due. Dr. Rüdel (Fraunhofer IME), Prof. Schröder (University of Vechta) and Dr. von der Trenck (LUBW) are up for re-election. Prof. Wiesmüller sees no more possibility of re-candidacy due to increased professional obligations. Further candidates are welcome. More Mitt Umweltchem Ökotox 4/2012

Main topic: Analysis of nanoparticles in complex media

Presentation by Dr. Frank von der Kammer, Head of the Nanogeosciences Group and the Colloid Laboratory, University of Vienna at the 15th meeting of the environmental monitoring Monitoring Working Group on November 27, 2009 at the Federal Environment Agency, Bismarckplatz 1, 14195 Berlin First of all, Mr von der Kammer discusses the definition of nanomaterials . This takes place via the size (<100 nm for at least one dimension), but the selected rigid limit does not necessarily make sense. In addition to engineered nano-particles (ENP), natural NPs are also present in the environment. In terms of size, natural NPs are a sub-fraction of the particles known as colloids, which range in size from 1 to 1000 nm. In contrast to the natural NPs, the technically produced ones are mostly very uniform. In environmental media, the NPs are mostly not present as free particles, but as aggregated clusters. Depending on the conditions, larger or smaller aggregates can form, including mixed aggregates, for example with biopolymers or inorganic particles. ENPs can also change in the environment (eg zinc NPs, which dissolve, or functionalised NPs in which the surface coating, the ?coating?, can be degraded). The environmental relevance of colloids has been discussed since 1989 because they can be carriers of contaminants (McCarthy and Zachara: Subsurface transport of contami-nants. Environ. Sci Technol 1989, 23: 496-502; link). Studies on the environmental relevance of technical NPs have only been available for a few years. About five years ago, the first studies on the effects of ENP on organisms (e.g. fish toxicity) became known. The analysis of ENP in complex matrices has so far only been partially successful. In this context, Mr von der Kammer refers to a statement by the EU food authority EFSA on the analysis of ENP in food (link). This deficit is also the background for an EU project in which the University of Vienna is involved and in which appropriate routine methods are to be developed. In situ methods for investigating NPs are not available so far, so that a sample preparation that changes the original conditions to a greater or lesser extent is necessary before the measurement. Depending on the question, the NPs in the sample must be stabilized, possibly pre-fractionated and finally enriched. Imaging methods such as electron microscopy are very helpful for examining NPs, as Herr von der Kammer impressively shows with a series of examples. However, the method is not suitable as the "gold standard", since artifacts can easily arise during preparation and the evaluation is subjective. In EM investigations, elements in the particles can also be analyzed with suitable devices (EDX, energy dispersive X-ray spectroscopy). Using this method, Kaegi et al. (Environ Pollut 2008) e.g. detect synthetic titanium dioxide NPs from paint in facade drains or Kiser et al. (ES&T 2009) Titanium dioxide NP in sewage sludge. The investigation with the 'laser induced breakdown spectrometry' (LIBD; measuring principle: plasma excitation and atomic emission spectrometry; link) is viewed as promising. Other methods that are suitable for the corresponding size range of the NP: atomic force microscopy, flow-field flow fractionation, light scattering methods (dynamic light scattering, DLS), scattering of X-rays and neutrons. Ultrafiltration or separations based on density (sedimentation / centrifugation) can also be useful for some questions. A light microscopic technique that can be used for certain purposes is nanoparticle tracking analysis (NTA). Here, in suspensions, the diffusion movement of the NPs is used to calculate their size distribution (from approx. 20-40 nm) and concentration. The choice of the appropriate method depends on the objective of the investigation. Should ENP only be detected or identified qualitatively, should they be quantified or should further characterization be carried out using its set of parameters? When quantifying, the question arises what exactly is to be determined: e.g. the number or concentration of NPs, the type or chemical composition (e.g. natural NP / ENP; carbon-based / metallic NP; possibly functionalized ones NP), the size or size distribution, the degree of agglomeration, the shape, the surface (so far only measurable for solids by means of gas adsorption using the BET method according to Brunauer, Emmett and Teller), the surface charge (e.g. as zeta potential), the pore volume ? It is becoming apparent that a single method is not sufficient for a comprehensive investigation. Herr von der Kammer explains that certain methods are only optimal for relatively homogeneous mixtures of NPs (e.g. light scattering, where large particles, due to measurement technology, interfere with the investigation of smaller NPs). The particle shape determined for NP also depends to a large extent on the measurement or evaluation method used (especially in the case of irregular particle shapes, only approximations). Another aspect that makes investigations of NPs complicated is that representative sampling, which does not change the NP distribution and agglomeration, from matrices such as soil, sediment or sewage sludge is difficult.
In the following, Herr von der Kammer goes into more detail on asymmetric flow-field flow fractionation (AF4). This technique for size separation of particles has great potential, since various detectors can be coupled to the separation chamber, which allow a comprehensive characterization of the NPs separated according to their size (e.g. UV, fluorescence, DLS, ICP-MS, TOF- MS). By coupling Flow-FFF and single particle ICP-MS, it was possible, for example, to detect platinum particles from car exhaust catalysts and tungsten particles from tire wear in street runoff water. The platinum NPs were not recognizable in the transmission EM because they were only present in very low concentrations. Finally, Mr. von der Kammer shows a number of examples that illustrate the possibilities of the various methods. His conclusion is that further investigations must clarify which are the critical parameters of the environmental relevance of NPs, that method-oriented research approaches are required, and that the various methods should be used in a complementary manner. The discussion showed that some colleagues are interested in a further exchange of information on the analysis of ENP as well as in joint process developments. Mr. von der Kammer also refers to the specialist committee "Aquatic Nanoscience and Nanotechnology" of the Society of Water Chemistry , which he heads.

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