6 Materialchemie
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Background: The ubiquitous occurrence of microplastic particles in marine and aquatic ecosystems was intensively investigated in the past decade. However, we know less about the presence, fate, and input paths of microplastic in terrestrial ecosystems. A possible entry path for microplastic into terrestrial ecosystems is the agricultural application of sewage sludge and solid bio-waste as fertilizers. Microplastic contained in sewage sludge also includes Polyethylene terephthalate (PET), which could originate as fiber from textile products or as a fragment from packaging products (foils, bottles, etc.). Information about microplastic content in such environmental samples is limited yet, as most of the used analytical methods are very time-consuming, regarding sample preparation and detection, require sophisticated analytical tools and eventually need high user knowledge.
Results: Here, we present a simple, specific tool for the analysis of PET microplastic particles based on alkaline extraction of PET from the environmental matrix and subsequent determination of the monomers, terephthalic acid, using liquid chromatography with UV detection (LC-UV). The applicability of the method is shown for different types of PET in several soil-related, terrestrial environmental samples, e.g., soil, sediment, compost, fermentation residues, but also sewage sludge, suspended particles from urban water management systems, and indoor dust. Recoveries for model samples are between 94.5 and 107.1%. Limit of determination and limit of quantification are absolute masses of 0.031 and 0.121 mg PET, respectively. In order to verify the measured mass contents of the environmental samples, a method comparison with thermal extraction-desorption-gas chromatography–mass spectrometry (TED-GC/MS) was conducted. Both methods deliver similar results and corroborated each other. PET mass contents in environmental samples range from values below LOQ in agriculture soil up to 57,000 mg kg−1 in dust samples.
Conclusions: We demonstrate the potential of an integral method based on chemical extraction for the Determination of PET mass contents in solid environmental samples. The method was successfully applied to various matrices and may serve as an analytical tool for further investigations of PET-based microplastic in terrestrial ecosystems.
All over the world, microplastic (MP) particles (particle size: 1 - 1.000 µm) are found in water, soil, air, biota and even food products. But plenty of these discussed findings are based on a very low number of real datasets, which are extrapolated to general projections. Furthermore, most data are not comparable because the strategies for sampling, sample preparation and detection methods are not harmonised/ or standardised. This would require extensive proficiancy tests. Because of the ubiquity presence and the unclear risks, which might arise from those particles, various political and environmental organisations (i.e. OECD, UNEP, WHO) identify the reduction of plastic entry in the environment as a key challenge for now and the future. This challenge includes the identification of relevant entry pathways but also the demand of harmonised, meaningful and reliable analytical procedures.
Regarding this task within the last few years, a fast practical solution for MP analysis has been developed, which includes the steps of representative sampling, adequate sample preparation and fast detection. Sampling is done by fractional filtration over sieves with mesh sizes of 500, 100, 50 and 5 µm [1]. The received samples are measured by ThermoExtraction/Desorption-Gas Chromatography-Mass Spectrometry (TED-GC-MS) [1,2]. for the most abundant polymers used in practice, which are polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyamide (PA) and acrylate as well as styrene-butadiene-rubber (SBR), a main component of tires.
The present presentation will give first-time insight in a comprehensive dataset of microplastic analysis for an exemplary urban sewage system. MP mass contents of different waters at several days, such as greywater, stormwater retention tank, influent and effluent of a wastewater treatment plant (WWTP) within an urban sewage system in Germany are determined. Furthermore, the mass of the polymers found in dry weather and rain weather flow are compared. The use of these large datasets allows first expressive conclusions regarding the contribution of urban sewage system to the MP entry sources in the environments.
We found PP and PS in all different waters. Furthermore, there is SBR in influent and also in effluent of the WWTP. Surprisingly, we could also detect hugh amounts of PE in the effluent of the WWTP.
Nanoparticle suspensions were microprinted onto TEM grids for subsequent analysis by SEM/TSEM and evaluation of particle numbers using Image J software. Various nanoparticle types, concentrations and printing conditions (temperature, rel. humidity) were evaluated in order to determine the optimal conditions for producing a uniform distribution of particles on the substrate and eliminating the coffee ring effect.
It is a well-known story that copolymers beside their molar mass distribution (MMD) can exhibit a functionality type distribution (FTD), a copolymer composition distribution (CCD), a monomer sequence distribution (MSD) and additionally different topologies within one sample. Small, often isobaric heterogeneities in topology or microstructure can usually not be simply separated chromatographically or distinguished by any common detector. Nowadays a wide range of different analytical separation techniques and multi-detection possibilities are available. The challenge consists in a clever combination of these techniques with a specific approach of data analysis. In this presentation different liquid chromatographic separation modes were combined with Electrospray Time-of-Flight mass spectrometry.
The online coupling allows the analysis of reconstructed ion chromatograms (RIC) of each degree of polymerization. While a complete separation often cannot be achieved, the derived retention times and peak widths lead to information on the existence and dispersity of heterogeneities in microstructure or topology, that are otherwise inaccessible This method is suitable to detect small differences in e. g. branching, topology, monomer sequence or tacticity and could potentially be used in production control of oligomeric products or other routinely done analyses to quickly indicate deviations from set parameters. Based on a variety of examples e.g. the topology elucidation of branched EO-PO copolymers, the possibilities and limitations of this approach were demonstrated.
The European legislation has responded to the wide use of nanomaterials in our daily life and defined the term “nanoform” in the Annexes to the REACH (Registration, Evaluation, Authorization of Chemicals) Regulation. Now specific information of the nanomaterials is required from the companies when registering the appropriate materials in a dossier.
In the context of REACH eleven physicochemical properties were considered as relevant, of which the following six are essential for registration of nanoforms (priority properties): chemical composition, crystallinity, particle size, particle shape, chemical nature of the surface (“surface chemistry”), and specific surface area (SSA). A key role is the reliable, reproduceable and traceable character of the data of these priority properties.
In this context, we want to discuss which ‘analytical’ information is exactly required to fulfill these conditions. Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) were chosen as the most popular surface analytical methods. Both methods allow a detailed understanding of the surface chemistry with an information depth below ten nanometers. As a rather bulk method for the analysis of nanoforms, Electron Probe Microanalysis (EPMA) in the version with energy dispersive X-ray spectroscopy (EDS) is considered for the quick identification of the main chemical elements present in the sample. Furthermore, Scanning Electron Microscopy (SEM) results are discussed which provide results on particle size and shape. Thus, four of the six priority properties can be obtained with these methods.
Based on practical examples of analysis with Electron Microscopy and Energy-Dispersive X-ray Spectroscopy, the minimum information requirements for reliable and reproducible nanomaterial characterization data such as particle size and shape distribution and elemental analysis are presented and discussed.
MISTRAL-Müller-Matrix-basierte Identifizierung von Inhomogenitäten und strukturellen Anomalien
(2020)
Mit abbildender Ellipsometrie (imaging ellipsometry: IE) können Nanometer-Beschichtungen/ Degradationen visualisiert und bezüglich Brechungsindex n, Extinktionskoeffizient k und Schichtdicke d charakterisiert werden. Materialseitig werden lokal Homogenität und Isotropie innerhalb eines/mehrerer Bildpunkte (field of analysis: FOA) und messtechnisch global die Ebenheit der Proben bezüglich aller Bildpunkte des Messfeldes vorausgesetzt. Für die Müller-Matrix-basierte abbildende Ellipsometrie (MM-IE), die den optischen Response anisotroper Materialien in jedem Bildpunkt über die bis zu 16 Müller-Matrix-Elemente erfasst, ist dies von besonderer Relevanz. Reale Substrate sind aber oft nicht eben, können lokal Noppen/Mulden (im FOA) aufweisen oder sind global konvex/ konkav im möglichen Messfeld (field of view: FOV) gekrümmt. Diese lokalen/globalen strukturellen Anomalien des Substrats werden schon für die IE messtechnisch/modellseitig oft nicht beherrscht und sind für die MM-IE in der Wirkung auf die MM-Elemente unbekannt. Diese Defizite sollen messtechnisch bzw. modellmäßig behoben und somit die Messung lokal/global gekrümmter Oberflächen ermöglicht werden (MM-CSIE, CS curved surface).
Irradiation with a single spatially Gaussian-shaped nanosecond laser pulse in the melting regime can result in a characteristic annular change in the surface morphology of crystalline silicon. This has been verified experimentally in a variety of situations, where dimple-shaped surface topographies are produced. In a recent work we have investigated the induced changes in the surface topography upon exposure to wavelengths in the visible and near infrared spectral region. Irradiation in the UV requires a more detailed analysis due to the enhanced absorption of the material. In the present analysis, we determine under which conditions our previous model can be used and the corresponding results are presented.
For the first time, dielectric and calorimetric investigations of an homologous series of Janus polynorbornenes with rigid main backbones and flexible -Si(OR)3 side groups, of differing length alkyl chains (R = Propyl, Butyl, Hexyl, Octyl, Decyl) is reported. Generally, this class of polymers has some potential for applications in the field of gas separation membranes. Two dielectrically active processes are observed at low temperatures, denoted as β- and α- relaxation. The former can be assigned to localized fluctuations, whilst the latter is related to the glassy dynamics of the flexible -Si(OR)3 side groups, creating a nanophase separation in both the alkyl chain rich and backbone rich domains. This is confirmed through temperature modulated DSC measurements and X-ray scattering experiments. The glass transition temperatures of the backbone rich domains, which are beyond or near to their degradation temperatures in terms of conventional DSC, are determined for the first time using Fast Scanning Calorimetry employing both fast heating and cooling rates. This is complimented with scattering experiments that show how the size of the alkyl chain rich domains increases with chain length. Alongside these results, a significant conductivity contribution was observed for all poly(tricyclononenes) with -Si(OR)3 side groups, which is interpreted in terms of a percolation model.