Comparative analysis of additive decomposition using one-dimensional and two-dimensional gas chromatography: Part I - Irganox 1010, Irganox 1076, and BHT

Plastics incorporate diverse additives, including primary antioxidants with a typical amount between 0.05 to 3 wt.%, to enhance plastics functionality and durability, preventing their oxidation and maintaining their mechanical properties. While these antioxidants offer substantial benefits, their degradation can significantly impact plastic pyrolysis by changing the pyrolysis oil product distribution. Understanding the intricate distribution of decomposition products resulting from pyrolysis is essential yet often overlooked. This study delved into the analysis of the decomposition of common primary antioxidants, namely, Irganox 1010, Irganox 1076, and butylated hydroxytoluene (BHT), utilizing both one–dimensional gas chromatography coupled with a quadruple mass spectrometer (GC–MS) and two–dimensional gas chromatography equipped with flame ionization detector and time–of–flight mass spectrometer (GC×GC–FID/TOF–MS). This study showed that GC×GC–FID/TOF–MS provided a more detailed characterization of the pyrolysis product distribution of primary antioxidants used in plastics in comparison to GC–MS. For each of the antioxidants, using the GC×GC–FID/TOF–MS analytical approach enhanced the identification of degradation products at least fivefold. Furthermore, GC×GC–FID/TOF–MS identified products of more chemical classes than GC–MS. For instance, compounds from 14 chemical classes were identified from GC×GC–FID/TOF–MS in the pyrolysis of Irganox 1010, whereas only 9 chemical classes were identified in GC–MS. Olefins were the major chemical class for both Irganox 1010 and Irganox 1076 in the decomposition process, accounting for 23.25 wt.% and 20.76 wt.%, respectively. Ketones were the major chemical class in the case of BHT, having a 6.68 wt.% yield. This research enhanced the understanding of the decomposition of primary antioxidant and their product distribution during pyrolysis and shed light on the potential necessity for using two-dimensional gas chromatography.