Identification of volatile impurities and thermal degradation products in sodium polyacrylate by headspace gas chromatography-mass spectrometry

Volatile organic compounds (VOCs) in the vapor phase above an industrial sample of sodium polyacrylate were investigated under various temperature conditions using gas chromatography-mass spectrometry combined with headspace analysis (HS-GC-MS), with the aim of identifying impurities and thermal degradation products. Conditions ensuring effective chromatographic separation of the degradation products mixture with acceptable resolution of major and minor component peaks were proposed. The sodium polyacrylate samples were thermostated at temperatures simulating operational (30 and 60°C) and extreme technological (190°C) conditions, both with and without air purging. The absence of VOCs in the original industrial sample after thermostating at temperatures up to 60°C was established. At 190°C, nine thermal degradation products and impurities were identified for the first time in the vapor phase, including propylene glycol, 1,4-butanediol, nonanal, dimethyl glutarate, alkyl acetals, bicyclic terpenes (cedrene, longifolene), and 2,6-di-tert-butylquinone (antioxidant degradation product). It was demonstrated that short-term purging of the sample with air at 190°C leads to a significant (by an order of magnitude) reduction in the concentrations of all identified VOCs. Based on an analysis of published toxicological data, it was concluded that the identified VOCs pose a low inhalation risk. The obtained results are important for developing safety measures for the high-temperature processing of sodium polyacrylate and confirm its status as a low-hazard material.