Promising techniques and open challenges for microplastic identification and quantification in environmental matrices
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Microplastics are observed ubiquitously and in different environmental compartments ranging from marine waters and sediments to freshwater and terrestrial ecosystems including biota. Over the last decade, several methods have been applied and advanced to monitor and quantify microplastics, to identify the polymer material and to describe the particle properties, such as size, shape or colour. In most cases, the overarching aim is to elucidate patterns of occurrence that might result from (micro)plastic emissions and environmental fate. But the applied methods are subject to uncertainties and boundary conditions, be it spatial resolution that excludes the smallest microplastics or limitations in distinguishing microplastic particles from natural particles. This critical review provides an overview of the state-of-the-art procedures in microplastic analysis, gives examples of potential ways ahead and remaining challenges and classifies available methods according to the underlying research question. The resulting decision tree for the selection of analytical methods starts with a common research question and takes specificities of the environmental matrix into account. The procedural range consequently ranges from fast screening methods based on visual identification to a highly sophisticated combination of analytical methods that provide information on polymer type, particle number or mass and eventually particle size but are very time-consuming and expensive. Standardization of microplastic analytical methods on the basis of the research aim will help to make study results comparable and obtain a more comprehensive picture of microplastic abundance and fate in the environment.
KeywordsExtraction Purification Infrared spectroscopy Raman spectroscopy Weathering
The author thanks Miriam Vogler and Carolin Huhn from the University of Tübingen for fruitful discussions on microplastic analysis and its challenges. Support by Franz Weyerer and Niklas Best in compiling literature on the costs of and time required for procedures in microplastic analysis is highly appreciated. The author acknowledges funding by the Excellence Initiative of the German Federal Ministry of Education and Research (BMBF) and the German Research Foundation (DFG) at the University of Tübingen. Special thanks for language correction goes to the team of Julia-Noreen Zarfl, Stuart Henderson and Mona Hakim.
Compliance with ethical standards
Conflict of interest
The author declares that she has no competing interests.
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