Method Development and Validation of Surrogate Organic Contaminants Analysis for Evaluation of the Recycled Polyethylene Terephthalate (rPET) Plastic Production Process by GC-MS

Method Development of Surrogate Contaminants in Recycled Plastic

Abstract

       The recycled Polyethylene terephthalate plastic (rPET) to be used as food packaging must be previously processed under efficient decontamination. According to the Notification of the Ministry of Public Health (No. 435) B.E. 2022, the decontamination steps in the recycling process must be displayed and the assessment of the surrogate contaminanttesting is required. This study aimed to develop a method for the determination of surrogate organic contaminants in PET following contaminants removal. In this study, flakes of plastic containers were added with 4 organic substance groups of surrogate contaminants which included volatile polar (chlorobenzene), volatile non-polar (toluene), non-volatile polar (benzophenone and methyl salicylate), and non-volatile non-polar (lindane). The flakes were extracted using organic solvent then analyzed by GC-MS technique. Method validation data was indicated that the specificity was acceptable. The calibration curves of surrogate groups showed the good linear range with R² value > 0.995. The LODs of surrogate groups 1−3 and 4 were 0.010 and 0.020 mg/kg, respectively, and the LOQs were 0.020 and 0.040 mg/kg, respectively. Accuracy and precision at 3 concentrations were investigated; %recovery, %RSD_r, and HORRAT were in the range of 86−102, 5.3−7.9, and 0.3−0.4, respectively. The analysis of PET plastic contaminated with all 4 groups of organic substances was monitored before and after cleaning under various conditions. In conclusion, the developed method is suitable for analysis of 4 groups of surrogate organic contaminant typically used to assess the efficiency of decontamination in the rPET production in compliance with legal requirements.