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Review article - Peer-reviewed, 2020

Sample Preparation Techniques for the Analysis of Microplastics in Soil-A Review

Thomas, Daniela; Schuetze, Berit; Heinze, Wiebke Mareile; Steinmetz, Zacharias


Although most plastic pollution originates on land, current research largely remains focused on aquatic ecosystems. Studies pioneering terrestrial microplastic research have adapted analytical methods from aquatic research without acknowledging the complex nature of soil. Meanwhile, novel methods have been developed and further refined. However, methodical inconsistencies still challenge a comprehensive understanding of microplastic occurrence and fate in and on soil. This review aims to disentangle the variety of state-of-the-art sample preparation techniques for heterogeneous solid matrices to identify and discuss best-practice methods for soil-focused microplastic analyses. We show that soil sampling, homogenization, and aggregate dispersion are often neglected or incompletely documented. Microplastic preconcentration is typically performed by separating inorganic soil constituents with high-density salt solutions. Not yet standardized but currently most used separation setups involve overflowing beakers to retrieve supernatant plastics, although closed-design separation funnels probably reduce the risk of contamination. Fenton reagent may be particularly useful to digest soil organic matter if suspected to interfere with subsequent microplastic quantification. A promising new approach is extraction of target polymers with organic solvents. However, insufficiently characterized soils still impede an informed decision on optimal sample preparation. Further research and method development thus requires thorough validation and quality control with well-characterized matrices to enable robust routine analyses for terrestrial microplastics.


plastic debris; microplastics; sample pretreatment; soil organic matter; density separation; digestion

Published in

2020, volume: 12, number: 21, article number: 9074
Publisher: MDPI

Authors' information

Thomas, Daniela
Johann Heinrich von Thunen Institute
Schuetze, Berit
Braunschweig University of Technology
Swedish University of Agricultural Sciences, Department of Soil and Environment
Steinmetz, Zacharias
University of Koblenz and Landau

UKÄ Subject classification

Environmental Sciences

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