The use of thermal desorption gas chromatography mass spectrometry (TD-GC-MS) to differentiate sources of plastic pollution.

Plastic pollution is an increasing global concern that has been shown to damage our environment. The current literature focuses on detecting the presence of plastic in environmental matrices, but little has been done to develop methods to identify the sources of plastic pollution. In this manuscript we present the use of thermal desorption gas chromatography mass spectrometry (TD-GC-MS) as a novel tool to undertake environmental forensics for plastics. Paired plastic samples were obtained from coastal waters and beaches in California and compared against store-bought equivalents. Samples were processed into the microplastic size range (of 1-5 mm) and analysed directly by TD-GC-MS. This research was able to identify unique potential marker features for four different polymers, showing that bulk characterisation by TD-GC-MS is possible. The chemical fingerprint was then further interrogated to show how it is possible to identify specific potential marker features that differentiate the same polymer produced by different manufacturers. This was evidenced through examples, first with biaxially-oriented PET (differentiating Mylar from PET) and then with latex (differentiating producers from the U.S.A. and China). This research demonstrates that environmental forensics for plastics is possible, and valuable diagnostic information can be gained from the chemical fingerprint. TD-GC-MS coupled with a statistically robust approach, and optionally as a complement to other techniques such as pyrolysis, offers a powerful tool for identifying the origins of pollution, allowing a more complete understanding of plastic pollution, but also enabling its effective regulation.