01/09/2020
Microplastic particles in soil. Chromatograms of terephthalic acid resulting from the extraction of PET particles from environmental samples.

Microplastic particles in soil. Chromatograms of terephthalic acid resulting from the extraction of PET particles from environmental samples.

Source: BAM Division Physical and Chemical Analysis of Polymers and Division Environmental Analysis

The knowledge about the occurrence of microplastics in soil is still limited. A possible entry path for microplastics is the agricultural fertilization with sewage sludge and solid bio-waste. Microplastics contained in sewage sludge includes polyethylene terephthalate (PET), which can originate as fiber from textile products or as a fragment of packaging products. However, information on the microplastics content in such environmental samples is still limited because available analytical methods are usually very time-consuming in terms of sample preparation and detection, require sophisticated analytical equipment and user knowledge. Here we demonstrate a simple, specific tool for the analysis of PET particles based on the alkaline hydrolysis of PET and extraction of the resulting terephthalic acid from the environmental matrix followed by subsequent determination using liquid chromatography with UV detection (LC-UV). The method requires minimal sample preparation and has been successfully used for different types of PET in several soil-related, environmental samples, e.g., soil, sediment, compost, fermentation residues, but also sewage sludge, suspended solids, and house dust. The PET mass contents range from a few ppm in agricultural soils to percents in dust samples. Method comparison with thermal-extraction-desorption-gas chromatography-mass spectrometry (TED-GC/MS) resulted in similar, mutually confirming results and verified the measurement of the presented method. Due to its robustness and the low investment of time and money, the presented method could also be extended to samples where PET contamination is particularly likely, for example, in the analysis of beverages in plastic bottles or for washing machine outflow.

Microplastic analysis using chemical extraction followed by LC‑UV analysis: a straightforward approach to determine PET content in environmental samples
Axel Müller, Caroline Goedecke, Paul Eisentraut, Christian Piechotta, Ulrike Braun
erschienen in Environmental Sciences Europe, Vol. 32, page 85 et seq.
BAM Division Physical and Chemical Analysis of Polymers, Division Environmental Analysis