Quantification of polyethylene in biodegradable plastics by analytical pyrolysis-based methods with GC split modulation

Two methods based on double-shot analytical pyrolysis-GC/MS (DSPy-GC/MS) and evolved gas analysis-MS (EGA-MS) were developed to quantify polyethylene (PE) in biodegradable plastics (BPs). BPs are widely used to produce short-lived goods such as shopping bags, packaging, and disposable tools. Small amounts of non-biodegradable plastics, namely PE, are added to BP formulations to reduce costs and improve processability. Current European regulations allow for a maximum 1% PE content by weight in biodegradable plastics, but no information is provided on how this content should be measured. The methods presented here were developed using a set of reference samples composed of common BP formulations with known added amounts of PE. The methods were tested for linearity, accuracy, matrix effect, and limits of detection and quantification. In the EGA-MS method, a new strategy based on mid-run split switch was developed, resulting in a significant increase of the signal of PE. Both methods proved capable of quantifying PE in concentrations of 1% or lower and showed negligible matrix interference. The EGA-MS method is faster, while the DSPy-GC/MS method provides lower limits of quantification. The results indicate that both methods could be used for routine quality control and conformity analysis of BPs. This is the first work describing quantification of PE in BPs using analytical pyrolysis-based techniques. The use of EGA-MS for quantitative analysis, and the use of mid-run split switch, are also presented in this paper for the first time.