Improved plastic detection in artificial soil using offline pyrolysis and TD-GC-MS/MS

Ryan Bartnick1, Andrey Rodionov1, Eva Lehndorff1
1 Soil Ecology

P 4.2 in Poster Session

An efficient method to quantify traces of plastic from different sources within soil matrices is needed to understand the fate of plastics in the terrestrial environment. Improvement of existing methods is needed to: a) minimize time-consuming clean-up of soil samples (i.e. removal of organic matter), b) increase selectivity, and c) simultaneously detect and quantify a variety of plastics. We analyzed 200-400 µm-scale polystyrene (PS), polyethylene (PE), polyethylene terephthalate (PET) and extracted characteristic MS/MS profiles using a new combination of large-scale pyrolysis with thermal desorption-gas chromatography-tandem mass spectrometry (TD-GC-MS/MS) and tested for overlap with organic matter. Pyrolysis products were transferred to on a non-polar sorbent, then subjected to gas chromatography. MS/MS profiles were derived from two electron ionizations of plastic pyrolysis products. These were successfully identified in mixes of plastics with sand and humic acids as model substances for soil matrices without removal of organic matter. We suggest SRM settings for five additional plastic polymers including biodegradables. Repeatability for PS, PE, and PET was shown with relative standard deviation (RSD) between 19% to 27% and linear regression (R2) between 0.80 to 0.98. Limit of detection was calculated to be 0.1, 0.03, and 0.01 µg g-1 for PE, PET, and PS respectively, using our novel method. This new method is a base to simultaneously evaluate a variety of microplastics in larger (>1 g) soil samples down to a concentration of 1 mg kg-1, potentially shortening analysis time from days to approximately 4 hours with prepared dry soil. Still, reference materials need to be developed and pyrolysis efficiency needs to be tested before quantification of the variety of microplastic in soils or other environmental matrices is possible.

Keywords: biodegradable plastic, gas chromatography-tandem mass spectrometry, microplastic, pyrolysis, soil
This site makes use of cookies More information