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Paper des Monats
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PFAS contamination poses significant challenges due to their persistence, bioaccumulation, and potential adverse effects on ecosystems and human health. In recent years, conventional treatment methods, such as incineration, photolysis, and chemical oxidation, have been applied for PFAS treatment. However, these technologies have limitations in terms of their efficacy and cost-effectiveness for efficient PFAS degradation. Consequently, researchers have explored alternative approaches such as photocatalysis, sonochemical degradation, oxidation, electrochemical degradation, and mechanochemical degradation also known as DMCR (Dehalogenation by Mechanochemical Reaction) to address the remediation challenge posed by PFAS contaminated environments. Lab scale experiments were conducted using a planetary ball mill, procured from Retsch GmbH Germany, equipped with 50 mL steel grinding jars under controlled conditions to investigate the degradation of perfluorooctanoic sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in contaminated model sand. The experiments were carried out in two stages: initially, with sand alone (15 g), and subsequently, with the addition of co-milling agents, that is, sodium metal (Na), Na with butylamine (BA), and Na with ethylenediamine (EDA) in different proportions.
From a metrological point of view, the analysis of micro and nanoplastics MNP requires not only representative and meaningful methods for sampling, preparation, and detection, but also defined and reproducible analytical procedures for the processes and materials used.
For such a validation of the detection procedures (including the determination of process and laboratory blank values), the filters and laboratory conditions used in interaction with the final MNP measurement play a central role for detection limits regarding MNP size, MNP content and statistical measurement control, in addition to the reference materials mentioned above. On the basis of available filtration materials (e.g. metal mesh, silicon, aluminum oxide, polycarbonate) and metrological boundary conditions, key aspects for metrologically sound method development must be defined.
Two key categories of analysis are developed for the characterization of MNP’s: analytical methods (e.g. µ-IR spectroscopy, µRaman) and mass spectrometry (eg. Py-GC/MS or TED-GC/MS). If in the first category the shape, size, number of particles and the size distribution present in the samples can be determined. In the second category the mass of the material can be measured and the volume of plastic present in the samples can be deduced from this. Both catagories are very sensitive in terms of the volume of material that can be analyzed; vibrational methods can detect single particles but mass-based method require enough particles to reach the limit of detection. That is why in this study we propose a filtration system, which in our opinion brings the two categories much closer to each other and allows true measurements of particle number and mass of the same sample. In this way it is possible not only to estimate the volume of plastic in the sample, but also to determine with much greater precision the number of particles and the type of plastic present. Furthermore, new methods for particle detection can be added and combined with existing methods. Our proposed system can be used for a single filter, but also for the use of several filters in cascade. In this way a separation of particles by size can be achieved.
This talk gives an overwiew about the material and physico chemical characterisation of materials developed for the EU founded project PlasticsFate. Particles in 1st and 2nd sample set are presented next to their characterisatin and documentation in data sheets. Some materials are prepared for reference material and used in an interlaboratory comparison. Results are briefly discussed.
In diesem Vortrag geht es um eine Übersicht über die Thematik der Mikroplastik, Was ist Mikroplastik, wie entsteht es und wo kommt es her. Es wird beschrieben wie eine repräsentative Probenahme erfolgen kann und wie welche Herausforderungen bei der Probenvorbereitung existieren. Die Detektion wird ausführlich beschrieben, sowohl mit Partikelanzahl als auch Masse. Im weiteren werden erste Referenzmaterialien und ihre Anwendung in internationalen Ringversuchen beschrieben. Der zweite Teil zeigt die Normungsaktivitäten im Bereich der Mikroplastik.
UFP-Emission beim 3D-Druck
(2024)
Desktop-3D-Drucker haben in der letzten Dekade große Popularität in Bildungseinrichtungen, kleinen Unternehmen und Privathaushalten erlangt. Weit verbreitet ist mittlerweile die „Fused Filament Fabrication (FFF)“ Technologie. Hier wird ein thermoplastisches Filament geschmolzen, durch eine Metalldüse extrudiert und anschließend schichtweise so auf ein Druckbett aufgetragen, dass ein 3D-Objekt entsteht. Das Filamentmaterial wird dabei thermisch stark belastet, was zur Emission von Aerosolen sowie flüchtigen organischen Verbindungen (VOC) führt. Dabei werden hauptsächlich ultrafeine Partikel (UFP, dP < 100 nm) freigesetzt werden, die sogar in manchen Fällen im sub-4nm Größenbereich einen signifikanten Anteil ausmachen können (Tang und Seeger 2024).
Die gesundheitliche Relevanz eingeatmeter UFP ist durch sehr viele Studien gut belegt. Während eines i.d.R. mehrstündigen FFF-Druckvorgangs wird ein Anwender mit diesen Luftschadstoffen im Innenraum exponiert, häufig ohne eine Einschätzung des damit verbundenen Risikos zu haben. Die Exposition kann durch technische Faktoren (z.B. Druckerausstattung und -einstellung, Innenraumventilation), aber auch erheblich durch die Filamentauswahl beeinflusst werden. Unser Vorschlag zur Risikominderung besteht in der Auszeichnung emissionsarmer Filamentprodukte mit dem Umweltzeichen „Blauer Engel“, um so den Verbrauchern eine fundierte Auswahl zu ermöglichen. In unserem Projekt entwickeln wir dafür ein kammerbasiertes, standardisierbares und robustes Prüfverfahren zur vergleichenden Messung der Emission aus Filamenten. Mit dem Strangdruck-Verfahren (engl. Strand Printing Method, SPM) wird eine festgelegte Filamentlänge mit konstanter Rate extrudiert und auf dem Druckbett abgelegt, ohne dabei ein 3D-Objekt aufzubauen. Diese Vorgehensweise reduziert den Einfluss experimentell schlecht zu kontrollierender Faktoren sowie die Ausfallquote. Eine detaillierte Beschreibung und die Vorteile von SPM werden in Tang und Seeger (2022) erläutert. SPM wurde bereits für 44 Filamentprodukte aus unterschiedlichen Polymeren und Additiven als Vergleichstest angewendet. Alle Messungen wurden in einer klimatisierten 1 m³-Emissionsprüfkammer durchgeführt. Die Gesamtanzahl der emittierten Partikel (TP) dient als Beurteilungsmaß, in Anlehnung an die Vergabegrundlage DE-UZ-219 des Umweltzeichens Blauer Engel für Laserdrucker. Unter den getesteten Filamentprodukten variiert TP um ca. vier Größenordnungen (1E+9 ≤ TP ≤ 1E+13). Auch innerhalb jeder der untersuchten Polymergruppen variierte TP signifikant. Die Partikelemission kann daher nicht allein nach dem Basispolymer kategorisiert werden. Unsere Resultate belegen, dass die Stärke der Partikelemission eher eine charakteristische und individuelle Eigenschaft eines Filamentproduktes ist. Die Herkunft der Polymere, die herstellerspezifischen Additive sowie die nicht deklarierte Verunreinigungen können einen starken Einfluss auf die Emission haben. Die Auszeichnung von emissionsarmen Filament-produkten verspricht somit eine einfache, aber effektive Maßnahme zu sein, um Verbrauchern eine Minderung des Expositionsrisikos beim FFF-3D-Druck zu ermöglichen.
ABSTRACT: Microorganisms often live in habitats characterized by fluid flow, and their adhesion to surfaces in industrial systems or clinical settings may lead to pipe clogging, microbially influenced corrosion, material deterioration, food spoilage, infections, and human illness. Here, a novel microfluidic platform was developed to investigate biofilm formation under precisely controlled (i) cell concentration, (ii) temperature, and (iii) flow conditions. The developed platform central unit is a single-channel microfluidic flow cell designed to ensure ultrahomogeneous flow and condition in its central area, where features, e.g., with trapping properties, can be incorporated. In comparison to static and macroflow chamber assays for biofilm studies, microfluidic chips allow in situ monitoring of biofilm formation under various flow regimes and have better environment control and smaller sample requirements.
Flow simulations and experiments with fluorescent particles were used to simulate bacteria flow in the platform cell for calculating flow velocity and direction at the microscale level. The combination of flow analysis and fluorescent strain injection in the cell showed that microtraps placed at the center of the channel were efficient in capturing bacteria at determined positions and to study how flow conditions, especially microvortices, can affect biofilm formation. The microfluidic platform exhibited improved performances in terms of homogeneity and robustness for in vitro biofilm formation. We anticipate the presented platform to be suitable for broad, versatile, and high-throughput biofilm studies at the microscale level.
In clinical magnetic resonance imaging, non-specific Gd-based contrast agents (GBCAs) are frequently used to improve image quality. However, the interaction of GBCAs with tissue components is not yet fully understood. Many diseases, including inflammation, fibrosis, and tumor invasion, are associated with characteristic changes of the extracellular matrix (ECM). The ECM is a three-dimensional scaffold that embeds the cells of all mammalian tissues. It is composed of structural proteins (e.g., collagen, elastin) and proteoglycans, which consist of glycosaminoglycans (GAGs) covalently bound to a protein core. GAGs are characterized by their ability to form complexes with cations such as lanthanides. Thus, GAGs could be a potential binding partner for GBCAs as a whole or for dechelated Gd. Laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA/ICP-ToF-MS) was used to investigate the uptake and distribution of different GBCAs in spheroids mimicking biological tissue and exhibiting different ECM expressions. Spheroids from Chinese hamster ovary (CHO) cells and GAG-depleted CRL-2242 cells were incubated with gadolinium chloride and various linear and macrocyclic GBCAs. Although all spheroids were exposed to identical Gd concentrations, differences in the amount of Gd taken up were observed. Gadolinium chloride is more strongly absorbed and accumulates mainly in the outer regions of the spheroids. In contrast, after incubation with linear and macrocyclic GBCAs, Gd is detected in the interior of both types of spheroids. Furthermore, differences in the Gd amount were found depending on the GBCA used. However, further studies are needed to elucidate such complex interactions, also using other (bio)analytical techniques.
Every day, there are new headlines in the media about microplastics (1-1000 µm, ISO/TR 21960:2020) and nanoplastics (< 1 µm, ISO/TR 21960:2020) findings all over the planet with high variations in particle number and mass. The challenges in analytics are very complex, e.g. representative sampling, non-destructive sample preparation with concentrated particles and homogeneous distribution and true detection. All together lead to lacks in harmonization and results, which are hardly comparable. On the other hand, monitoring of microplastics is mandatory in the future strictly regulated by the EU commission in the Drinking water and Wastewater Framework Directive. One step to accurate and precise results will be the development of suitable reference materials mimicking particles in the environment.
BAM developed test materials, which are produced by mixing a small portion of microplastic particles with a water-soluble matrix. After solid phase dilution and homogenisation small portions are pressed into tablets and bottled in glass vials (Figure 1). These tablets are well characterized with particle size distribution and SEM images. Additionally, they are tested as reference material candidate according to homogeneity and stability for particle number with µ-IR and µ-Raman as well as on particle mass with Py-GC/MS and TED-GC/MS after ISO Guide 35. Results are promising. The material passed the homogeneity control. No changes are observed within 6 months of storage.
The same tested reference material is finally used in sample preparation experiments, where environmental suspended particular matter from surface water or baby milk powders are spiked with the tablets.
Over the last 20 years, many researchers, politicians and citizens have become increasingly aware of the growing plastic problem of our time. A lack of recycling concepts and plastic collection points as well as careless dumping lead to accumulation of plastic products in the environment. Natural weathering can cause these plastics to degrade and fractionate, meaning that microplastics (1 1,000 µm, ISO/TR 21960:2020) and nanoplastics (< 1 µm, ISO/TR 21960:2020) of various synthetic polymer materials can now be detected in all parts of the world. Whether microplastics or nanoplastics pose a toxicological hazard is being investigated in a variety of ways. Valid results are still pending. However, the EU precautionary principle applies to micro- and nanoplastics. Monitoring of microplastics is already required in the revision of the Drinking Water and Wastewater Framework Directive.
Reliable monitoring of rivers can be carried out by sampling with sedimentation boxes and microplastic detection by using thermal extraction desorption gas chromatography/mass spectrometry (TED-GC/MS) in routine operation (Figure 1). The river Rhine was sampled for microplastic masses at three different sampling locations over a period of one year and in addition the Danube at randomized sampling locations The TED-GC/MS results showed that various synthetic polymers frequently produced in industry, such as polyethylene, polypropylene or polystyrene as well as the tire compound styrene-butadiene rubber were found. The work not only shows a possible workflow for monitoring concepts, but also provides information on environmentally relevant concentrations of microplastics and tire components in surface waters. This in turn is necessary for ecotoxicological studies.
Microplastic determination in food and surface waters will be increasingly carried out in the course of future directives and regulations, such as EU drinking water directive and wastewater directive. In addition to unique identification, this also includes reliable quantification. Two different methodological approaches are used for the quantification. With vibrational spectroscopic techniques such as µ-FTIR and µ-Raman, results are obtained in the form of particle number, size and shape. Instead, with thermal analytical technics as TED-GC/MS and Py-GC-MS the results are expressed as mass concentration.. Both concepts offer different information variables. In terms of routine monitoring, it is necessary to obtain a rapid sequence from sampling to the detection result. For this reason, this study focuses on TED-GC/MS and Py-GC-MS. Even though thermal analytical methods generally require less sample preparation, some matrices require it. This is usually done if the analyte concentration is too low or if strong matrix effects such as signal suppression and false positive signals occur.
This talk presents advanced sample preparation for baby milk powder as food example and density separation for microplastic analysis in surface waters.
A preparation protocol based on citric acid was selected for the milk to remove as much as possible of the matrix. The low pH value leads to a fast and effective protein precipitation and minimizes filter cake formation, making filtration possible, reduces the number and the amount of compounds in detection and hence, simplifies the evaluation.
Microplastics in surface waters and sediments must be concentrated not only because of their low microplastics mass content but also in terms of homogeneity. For this purpose, a density separation was carried out using a concentrated sodium iodide solution, which led to a high reduction of the inorganic mineral matrix and made possible to obtain a representative subsample of initial masses of up to 80 g.