Decomposability versus detectability: First validation of TED-GC/MS for microplastic detection in different environmental matrices

Abstract

A fast method for microplastic detection is thermal extraction desorption-gas chromatography/mass spectrometry (TED-GC/MS), which uses polymer-specific thermal decomposition products as marker compounds to determine polymer mass contents in environmental samples. So far, matrix impacts of different environmental matrices on TED-GC/MS performance had not yet been assessed systematically. Therefore, three solid freshwater matrices representing different aquatic bodies with varying organic matter contents were spiked with a total of eight polymers. Additionally, for the first time, the two biodegradable polymers polybutylene adipate terephthalate (PBAT) and polylactide (PLA) were analysed using TED-GC/MS. The methodological focus of this work was on detectability, quality of signal formation as well as realisation of quantification procedures and determination of the limit of detection (LOD) values. Overall, TED-GC/MS allowed the unambiguous detection of the environmentally most relevant polymers analysed, even at low mass contents: 0.02 wt% for polystyrene (PS), 0.04 wt% for the tyre component styrene butadiene rubber (SBR) and 0.2 wt% for polypropylene (PP), polyethylene (PE) and PBAT. Further, all obtained LOD values were increased in all matrices compared to the neat polymer without matrix. The LOD of the standard polymers were increased similarly (PS: 0.21–0.34 µg, SBR: 0.27–0.38 µg, PP: 0.32–0.36 µg, PMMA: 0.64–1.30 µg, PET: 0.90–1.37 µg, PE: 3.80–6.99 µg) and their decompositions by radical scission processes were not significantly influenced by the matrices. In contrast, matrix-specific LOD increases of both biodegradable polymers PBAT (LOD: 1.41–7.18 µg) and PLA (0.84–20.46 µg) were observed, probably due to their hetero-functional character and interactions with the matrices. In conclusion, the TED-GC/MS performance is not solely determined by the type of the polymers but also by the composition of the matrix.