Analytica Chimica Acta 687 (2011) 67–74 Contents lists available at ScienceDirect Analytica Chimica Acta journal homepage: www.elsevier.com/locate/aca Pros and cons of analytical methods to quantify surrogate contaminants from the challenge test in recycled polyethylene terephthalate Juliana S. Félix, Pilar Alfaro, Cristina Nerín ∗ Department of Analytical Chemistry, Aragon Institute of Engineering Research (I3A), CPS, University of Zaragoza, Torres Quevedo Bldg., María de Luna St. 3, E-50018 Zaragoza, Spain article info Article history: Received 30 August 2010 Received in revised form 24 November 2010 Accepted 8 December 2010 Available online 16 December 2010 Keywords: Recycled polyethylene terephthalate Surrogates Challenge test Headspace-solid-phase microextraction Gas chromatography–mass spectrometry abstract Different analytical methods were optimized and applied to quantify certain surrogate contaminants (toluene, chlorobenzene, phenol, limonene and benzophenone) in samples of contaminated and recy- cled flakes and virgin pellets of polyethylene terephthalate (PET) coming from the industrial challenge test. A screening analysis of the PET samples was carried out by direct solid-phase microextraction (SPME) in headspace mode (HS). The methods developed and used for quantitative analysis were a) total dissolu- tion of PET samples in dichloroacetic acid and analysis by HS-SPME coupled to gas chromatography–mass spectrometry (GC–MS) and, b) dichloromethane extraction and analysis by GC–MS. The concentra- tion of all surrogates in the contaminated PET flakes analyzed by HS-SPME method was lower than expected according to information provided by the supplier. Dichloroacetic acid interacted with the sur- rogates, resulting in a tremendous decrease of limonene concentration. The degradation compounds from limonene were identified. Dichloromethane extraction and GC–MS analysis evidenced the highest values of analytes in these PET samples. Based on the foregoing data, the efficiency of the recycling process was evaluated, whereby the removal of 99.9% of the surrogates proceeding from the contaminated flakes was confirmed. © 2010 Published by Elsevier B.V. 1. Introduction PET is one of the most promising plastic for recycling in view of the low content of additives in the virgin material, low diffusivity and low uptake characteristics, and also due to the large number of PET bottles currently wasted [1–3]. The possibility of using recy- cled PET which will come into contact with food creates the need to develop efficient and sensitive analytical methods applicable to the identification and quantification of contaminants from recy- cled PET, which would also evidence that this recycled material complies with the terms of legislation. The recycling processes of PET for direct food contact have to evidence efficiency of contaminant removal and ensure consumer protection. The challenge test is a tool for this purpose [4,5]. Vir- gin polymer (either in pellets, container form or flakes) is soaked in a solution containing high concentration of selected surrogate contaminants, and then the exposed polymer is recycled (thermo- mechanical reprocessing (e.g., sorting, washing, grinding, melting, and pelletizing) and/or chemical treatment). Subsequent analysis of the contaminated polymer and the recycled one will provide evidence on the efficiency of the recycling process. ∗ Corresponding author. Tel.: +34 976 761873; fax: +34 976 762388. E-mail addresses: jfelix@unizar.es (J.S. Félix), palfarot@unizar.es (P. Alfaro), cnerin@unizar.es (C. Nerín). In 2008, the EU Commission adopted the challenge test as a requirement for the production of recycled plastics intended to come into contact with food [6–10]. Furthermore, the recycled plas- tic materials must be in accordance with the Regulations (EC) No 1935/2004 [11], (EC) No 2023/2006 [12] and (EC) No 282/2008 [6] and, additionally, these materials must comply with Directive 2002/72/EC [13]. Vilaplana and Karlsson [14] identified three key properties for quality assessment of recycled plastics: the degree of mixing (com- position), the degree of degradation, and the presence of low molecular weight compounds. These key properties are necessary to fully guarantee the applicability of recyclates for the manufac- ture of new products. However, when these recycled materials are intended for direct food contact the key issue for any recycling pro- cess has to be the decontamination of post-consumer compounds or substances from misuse to levels down to the range of impurities of virgin PET materials [15]. According to EFSA [7], experimental or theoretical considerations on the possible migration of contam- inants from recycled plastic intended to come into contact with food should be also clearly defined and relevant scientific evidence supported by appropriate documentation and/or scientific litera- ture should be provided. As safety and technical cleaning efficiency criteria, the migration of each surrogate from recycled packaging into food must not exceed 10 g kg -1 [8,10]. It is also important to note that FDA reported that the estimated daily intake (EDI) of contaminants migrating from recycled food-contact articles in the 0003-2670/$ – see front matter © 2010 Published by Elsevier B.V. doi:10.1016/j.aca.2010.12.013