Chemical contamination
is one of the major obstacles for mechanical
recycling of plastics. In this article, we built and open-sourced
an in-house MS/MS library containing more than 500 plastic-related
chemicals and developedmspcompiler,an R package,
for the compilation of various libraries. We then proposed a workflow
to process untargeted screening data acquired by liquid chromatography
high-resolution mass spectrometry. These tools were subsequently employed
to data originating from recycled high-density polyethylene (rHDPE)
obtained from milk bottles. A total of 83 compounds were identified,
with 66 easily annotated by making use of our in-house MS/MS libraries
and themspcompilerR package. In silico fragmentation
combined with data obtained from gas chromatography–mass spectrometry
and lists of chemicals related to plastics were used to identify those
remaining unknown. A pseudo-multiple reaction monitoring method was
also applied to sensitively target and screen the identified chemicals
in the samples. Quantification results demonstrated that a good sorting
of postconsumer materials and a better recycling technology may be
necessary for food contact applications. Removal or reduction of non-volatile
substances, such as octocrylene and 2-ethylhexyl-4-methoxycinnamate,
is still challenging but vital for the safe use of rHDPE as food contact
materials.