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Monitoring of microplastics in food matrices is crucial to determinate the human exposure. By direct ingestion microplastics could be released in the food during the production, through packaging and by consumer’s use. The absence of standard methods to quantify and detect different size range and type of microplastics has led to difficult and time consuming procedural steps, poor accuracy and lack of comparability. In this work, matrix characterization and laboratory experiments were used to investigate the efficiency of sample preparation in milk powder. This information is crucial to compile a standard procedure for sample preparation and digestion of common milk powder to detect different particle sizes and types of polymers. Charaterisation is done by TGA and TOC measurements.
AbstractMicroplastics (MP) can be detected in all environmental systems. Marine and terrestrial aquatic systems, especially the transported suspended solids, have often been the focus of scientific investigations in the past. Sediments of aquatic river systems, on the other hand, were often ignored due to the time‐consuming sample preparation and analysis procedures. Spectroscopic measurement methods counting particle numbers are hardly suitable as detection methods, because there are plenty of natural particles next to a small number of MP particles. Integral methods, such as thermoanalytical methods are determining the particle mass independently of the inorganic components.In this study, a workflow for sample preparation via density separation and subsequent analysis by thermal extraction desorption‐gas chromatography/mass spectrometry is presented, which leads to representative and homogeneous samples and allows fast and robust MP mass content measurements suitable for routine analysis. Polymers were identified and quantified in all samples. Polyethylene and styrene‐butadiene rubber are the dominant polymers, besides polypropylene and polystyrene. Overall, total polymer masses between 1.18 and 337.0 µg/g could be determined. Highest MP concentrations in riverbed sediment are found in sites characterized by low flow velocities in harbors and reservoirs, while MP concentrations in sandy/gravelly bed sediments with higher flow velocities are small.
Inputs of plastic impurities into the environment via the application of fertilizers are regulated in Germany and the EU by means of ordinances. Robust and fast analytical methods are the basis of legal regulations. Currently, only macro- and large microplastic contents (>1 mm) are measured. Microplastics (1–1,000 µm), are not yet monitored. Thermal analytical methods are suitable for this purpose, which can determine the mass content and can also be operated fully automatically in routine mode. Thermal extraction desorption-gas chromatography/mass spectrometry (TED-GC/MS) allows the identification of polymers and the determination of mass contents in solid samples from natural environments. In accordance with the German or European Commission (EC) Fertiliser Ordinance, composting plants should be monitored for microplastic particles with this method in the future. In this context a compost plant was sampled. At the end of the rotting process, the compost was sieved and separated in a coarse (>1 mm) and a fine fraction (<1 mm). The fine fraction was processed using density separation comparing NaCl and NaI as possible salt alternative and screened for microplastic masses by TED-GC/MS with additional validation and quality assurance experiments. With TED-GC/MS total microplastics mass contents of 1.1–3.0 μg/mg in finished compost could be detected with polyethylene mainly. What differs much to the total mass of plastics in the coarse fraction with up to 60 μg/mg, which were visually searched, identified via ATR-FTIR and gravimetrically weighted.
Microplastics are widely distributed in aquatic and terrestrial environments, up to now less is known on toxicological impacts under realistic conditions. Research so far has focused mainly on the impacts on organisms by fresh plastic fragments or beats. However, plastic materials found in the environment are mainly a mixture of different polymers and particularly degraded during aging processes. Although especially oxidized degradation products might escape from plastic materials during aging, there is a lack of information on potentially adverse effects on aquatic biota. The latter is of particular interest as oxidized chemicals become more water soluble due to higher polarity and are more bio-available, therefore.
The present study focussed on plastic leachates of polystyrene (PS) and polylactic acid (PLA), which were derived from alternating stress by hydrolysis and UV radiation. Test specimen of PS, PLA or PS/PLA blends (each 50 %) were alternatingly maintained in water at 45 °C for five days and UV radiated at 45 °C for two days, for in total six weeks. Ecotoxicological effects of potentially generated degradation products of plastic materials in the storage water (mineral water, pH: 7.2) were detected by algae growth inhibition tests with Desmodesmus suspicatus and photosystem II inhibition tests with Raphidocelis subcapitata.
Results clearly indicate inhibitory effects on algae growth by contaminants in the storage water of stressed plastic materials with increasing growth inhibition of proceeding hydrolysis and UV stress times. Here, different plastics cause variable responses of algal growth. First chemical analyses indicate dissolved monomers and their oxidation products of plastic materials as possible driver of detected ecotoxicological effects, since detected microplastic particles do not seem to harm algae.
The existing data highlight the relevance of plastic aging as a framework for microplastic ecotoxicity evaluation and allow a proof of concept.
The formation of microplastic (MP) particles (1-1000 µm) is mostly related to physicochemical degradation processes of macroplastics. Photooxidative damage is often set as the initial degradation process, which leads to embrittlement of the plastics. Mechanical processes then lead to further fragmentation and the formation of MP particles. In the environment, this can be associated with UV exposure through direct radiation from the sun, which leads to radical formation in the polymer systems on the one hand and radical formation of oxygen on the other. The result is material embrittlement usually caused by chain shortening in the polymeric system. Due to specific ecosystem conditions, the damaged polymer is fragmented by erosive, abrasive processes or wave action.
According to reference material topic for MP analysis, pristine and artificially weathered polymers are needed. Starting from granulate or macroplastics, these can be pulverised with different techniques, bottled and stored until usage. The bottled powders need to be homogen and stable over a defined time interval regarding to a specific property.
This work deals with different polymer types, aged and non-aged. It tries to answer the question under which storage conditions polymers will be stable in particle size. The powders are characterized for chemical composition and shape with FTIR, DSC and SEM. Particle size distribution was measured by laser diffraction with wet and dry dispersion. Artificially pre-aged materials seem to be more vulnerable for further aging and less stable in particle size distribution measurements.