Gas chromatography-ion mobility spectrometry for the quantification of recycled polyethylene terephthalate in food packaging

The poorer quality and price of recycled plastic discourage the implementation of circular economy, so governments promote its use through laws that establish minimum contents of recycled material. The presence of volatile organic compounds (VOCs) , in recycled plastic hinders its application as a material in contact with food. In order to control the quality of polyethylene terephthalate (PET) and ensure compliance with legislation, an analytical methodology based on the monitoring of VOCs by headspace gas chromatography coupled to ion mobility spectrometry (HS-GC-IMS) was developed and validated. Spectra of PET trays with different percentages of recycled PET were analyzed in a non-targeted way. Sixteen VOCs, mostly aldehydes, were identified in the samples. The limitations in the identification which IMS databases still have were brought to light. With limits of quantification of up to 0.25 ng g −1 , VOCs were quantified obtaining higher concentrations in recycled PET (rPET) than in virgin PET, using calibration curves based on the Boltzmann's equation. With GC-IMS data, an orthogonal partial least squares discriminant analysis (OPLS-DA) model allowed to detect the presence of rPET and estimate its amount (100 % correct classification, R2X(cum) = 0.861, R2Y(cum) = 0.957 and Q2(cum) = 0.932). In addition, a partial least squares (PLS) regression model with an R 2 of 0.994 was also designed to more accurately quantify the percentage of rPET in a sample with standard deviation lower than 3 %. Environmental sustainability, minimal sample treatment and short analysis time (19 min) make this methodology a promising tool for its application in industry or governmental controls. • GC-IMS as an alternative greener than GC–MS to monitor the quality of plastic. • Untargeted monitoring of volatile organic compounds in PET. • Evaluation of the identification power of IMS database. • Detection of recycled PET and estimation of its share in food packaging. • VOCs are generally found in higher concentration in recycled PET.