Introducing a novel approach for microplastic analysis in river sediments

, Kurzweg Lucas, Schirrmeister Sven, Adomat Yasmin, Harre Kathrin, Socher Martin.

Microplastics (MP) in environmental compartments are a topic of growing concern. The understanding of fate and impact of microplastic is still hampered by a lack of comparability between studies and time-consuming processing and analysis methods. Therefore, the establishment of a reliable and cost-efficient method for environmental monitoring is urgently required. Most of the common used methods do not fit all requirements. They may not give chemical confirmation of the polymer or are highly time-consuming. Here we want to present a novel approach for MP analysis in river sediments combining electro separation (corona roller separator, Hamos, Prenzberg, Germany) and differential scanning calorimetry (DSC, Netzsch, Germany). Microplastic particles of ultra-high molecular weight polyethylene (PE-UHMW, size range: 100 to 200 µm) were separated from particulate matrices such as river sediment or sand. Samples with MP concentrations from 100 to 1 ppm (parts per million) PE-UHMW were investigated. Recovery rates of the polymer in the enriched fractions were determined using the thermodynamic fingerprints measured by DSC. The pattern of the DSC curve with phase transition temperatures and enthalpies allows the identification and quantification of the polymer type. Electro separation removed 99.91 ± 0.03 percent of the initial matrix from an artificial sediment. In environmental samples, 93.0 ± 1.0 percent to 99.52 ± 0.06 percent of the initial matrix were removed, depending on the particle size distribution, bulk density and total organic carbon. The recovery rate for the PE-UHMW was determined as 91 ± 5 percent in the artificial sediment. We determined the limit of quantification to 40 ppm and the limit of identification to 1 ppm. Recovery rates are lower for environmental samples then for artificial matrices. Moreover, 5 samples could be processed in 8 hours after drying. In conclusion, our approach has potential as a reliable and fast method for monitoring of highly polluted environmental compartments.

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