New method for extraction, identification and quantification of Non-Intentionally Added Substances (NIAS) in polystyrene

An efficient one-step extraction method was developed for the recovery of additives and Non-Intentionally Added Substances (NIAS) from polystyrene, performed at room temperature for 2.33 hours, without grinding to avoid fostering the formation of NIAS unrelated to polymer processing. Solvent use (39.2 mL/g) was greatly reduced compared to extraction conditions previously reported. The study of NIAS is analytically challenging but with high importance since their presence is a potential threat to human health and to the environment while reducing plastic potential recyclability. For an understanding of NIAS formation and influence of processing parameters, a systematic approach was taken, using virgin polystyrene mixed with known quantities of standard additives as model materials (Irganox_1076, Tinuvin_326, Irgafos_168). The degradation of one additive was identified by NMR and GC-MS. Precise multiple-point quantification with internal standard was performed by GC-MS, measuring a 5.1 wt% Irgafos_168 degradation, with additives LOD ranging from 0.55-0.95 ppm. Evaluation of analytical challenges, such as matrix effects, was discussed and quantified. This method will help the quality control of virgin and recycled PS materials, including food contact ones, and improve the knowledge of PS processing impact on NIAS formation.