Catalytic behavior of nitrous acid for acetaminophen transformation during the freezing process

• Published in: Journal of hazardous materials 2023-08, Vol.456, p.131652-131652, Article 131652
• Main Authors: Ahn, Yong-Yoon, Kim, Jungwon, Kim, Kitae
• Format: Article
• Language: English
• Subjects: Abnormal stoichiometry; acetaminophen; aqueous solutions; Arctic region; catalytic activity; dissolved oxygen; electron paramagnetic resonance spectroscopy; electrospray ionization mass spectrometry; environmental science; Freeze concentration; Ice; lakes; Nitrite; nitrites; nitrous acid; oxidation; Pharmaceuticals; polymerization; species; stoichiometry; tandem mass spectrometry
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.131652

This study demonstrates the transformation of acetaminophen by reactive nitrous acid in a frozen solution and its abnormal stoichiometry. The chemical reaction between acetaminophen and nitrous acid (AAP/NO2− system) was negligible in the aqueous solution; however, the reaction rapidly progressed if the solution started to freeze. The ultrahigh performance liquid chromatography–electrospray ionization tandem mass spectrometry measurements showed that polymerized acetaminophen and nitrated acetaminophen were formed in the proceeding reaction. Electron paramagnetic resonance spectroscopy measurements showed that nitrous acid oxidized acetaminophen via a one-electron transfer reaction producing acetaminophen-derived radical species, which is the cause of acetaminophen polymerization. We demonstrated that a relatively smaller dose of nitrite than acetaminophen caused significant acetaminophen degradation in the frozen AAP/NO2− system and revealed that the dissolved oxygen content notably affected acetaminophen degradation. We showed that the reaction occurs in a natural Arctic lake matrix (nitrite and acetaminophen spiked). Considering that the freezing phenomenon is common in the natural environment, our research provides a possible scenario for the freezing chemistry of nitrite and pharmaceuticals in environmental chemistry. [Display omitted] •Acetaminophen transformation was much larger than the nitrite concentration during the freezing process.•Nitrite and dissolved oxygen introduced a chain reaction in the freezing-induced chemical system.•Acceleration of the reaction was ascribed by freeze concentration effect and pH change in the ice grain boundary region.•The polymerized and nitrated acetaminophen compounds are detected as a product of reaction.•The transformed pharmaceutical compounds may exert potential risks to the environment.