Quantification of Recycled Polypropylene Stabilizers for Quality Control by Liquid Chromatography–Tandem Mass Spectrometry Using Simple, Fast and Efficient Ultrasonic Extraction

Abstract

Identifying and quantifying stabilizers in recycled plastics is crucial for utilizing recycled plastics in high‐value‐added applications while avoiding inhibitory effects between additives. However, identifying and quantifying stabilizers composed of multiple chemical classes with different chemical structures presents significant challenges. In this study, the time‐dependent extraction of 17 stabilizers, including six phenolic antioxidants, two phosphite antioxidants, two sulfur antioxidants, two hindered amine light stabilizers (HALS), and five ultraviolet absorbers, from a model polypropylene (PP), was investigated to observe the extraction behavior of these stabilizers. Using ultrasonic extraction on cryogenically ground PP powder, the 17 stabilizers were extracted almost quantitatively within a short duration of 1 h. Utilizing the developed extraction method, stabilizers in 10 types of commercially available recycled PP were quantified by liquid chromatography–tandem mass spectrometry, and no significant matrix effects were observed. On average, nine types of stabilizers were detected per sample, highlighting the complexity of the stabilizer formulations in recycled PP. Sulfur antioxidants and HALS, which require caution due to their inhibitory effects, were found simultaneously in five samples, underscoring the importance of identifying and quantifying stabilizers in recycled PP.