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Type: Article × Subject: Micro-Raman spectroscopy ×

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    Analysis of microplastics in drinking water and other clean water samples with micro-Raman and micro-infrared spectroscopy: minimum requirements and best practice guidelines
    (Berlin [u.a.] : Springer, 2021) Schymanski, Darena; Oßmann, Barbara E.; Benismail, Nizar; Boukerma, Kada; Dallmann, Gerald; von der Esch, Elisabeth; Fischer, Dieter; Fischer, Franziska; Gilliland, Douglas; Glas, Karl; Hofmann, Thomas; Käppler, Andrea; Lacorte, Sílvia; Marco, Julie; Rakwe, Maria El; Weisser, Jana; Witzig, Cordula; Zumbülte, Nicole; Ivleva, Natalia P.
    Microplastics are a widespread contaminant found not only in various natural habitats but also in drinking waters. With spectroscopic methods, the polymer type, number, size, and size distribution as well as the shape of microplastic particles in waters can be determined, which is of great relevance to toxicological studies. Methods used in studies so far show a huge diversity regarding experimental setups and often a lack of certain quality assurance aspects. To overcome these problems, this critical review and consensus paper of 12 European analytical laboratories and institutions, dealing with microplastic particle identification and quantification with spectroscopic methods, gives guidance toward harmonized microplastic particle analysis in clean waters. The aims of this paper are to (i) improve the reliability of microplastic analysis, (ii) facilitate and improve the planning of sample preparation and microplastic detection, and (iii) provide a better understanding regarding the evaluation of already existing studies. With these aims, we hope to make an important step toward harmonization of microplastic particle analysis in clean water samples and, thus, allow the comparability of results obtained in different studies by using similar or harmonized methods. Clean water samples, for the purpose of this paper, are considered to comprise all water samples with low matrix content, in particular drinking, tap, and bottled water, but also other water types such as clean freshwater.
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    Comparison of bacteria in different metabolic states by micro-Raman spectroscopy
    (New York, NY [u.a.] : Elsevier, 2022) Shen, Haodong; Rösch, Petra; Thieme, Lara; Pletz, Mathias W.; Popp, Jürgen
    It was shown that several metabolic states of bacteria with various characteristics such as chemical composition participate in the formation of biofilms. To study the connections and differences among different bacterial metabolic states, five species of bacteria in exponential phase, stationary phase and biofilm have been compared and investigated by micro-Raman spectroscopy. The spectral differences between different metabolic states showed that the chemical composition varied among those metabolic states. Moreover, as can be shown by the spectral differences and principal components (PCs), different species and strains of bacteria behave differently. Furthermore, a principal component analysis (PCA) combined with support vector machines (SVM) was applied to distinguish species of bacteria within the same metabolic states. Our study provides valuable data for the comparison of bacteria between different metabolic states utilizing micro-Raman spectroscopy in combination with chemometrics models.