title: Organophosphate Flame Retardants and Plasticizers in Aqueous Solution: pH-Dependent Hydrolysis, Kinetics, and Pathways.
abstract: Despite the growing ubiquity of organophosphate (OP) triesters as environmental contaminants, parameters affecting their aquatic chemical stabilities are currently unknown. The present study examined the pH-dependent (7, 9, 11, or 13) hydrolysis of 16 OP triesters in mixtures of 80 ng/mL for each OP triester over a period of 35 days at 20 °C. For the pH = 7, 9, and 11 solutions, 10 of the 16 OP triesters were stable and with no significant (p > 0.05) degradation. For the remaining 6 OP triesters, significant degradation occurred progressing from the pH = 7 to 11 solutions. At pH = 13, except for tributyl phosphate and tris(2-ethylhexyl) phosphate, 14 OP triesters were degraded with half-lives ranging from 0.0053 days (triphenyl phosphate) to 47 days (tripropyl phosphate). With increasingly basic pH the order of OP triester stability was group A (with alkyl moieties) > group B (chlorinated alkyl) > group C (aryl). Numerous OP diesters were identified depending on the pH level of the solution, whereas OP monoesters were not detectable. This is consistent with no significant (p > 0.05) depletion observed for 5 OP diesters in the same 4 solutions and over same 35 day period, suggesting OP diesters are end products of base-catalyzed hydrolysis of OP triesters. Our results demonstrated that pH-dependent hydrolysis of OP triesters does occur, and such instability would likely affect the fate of OP triesters in aqueous environments where the pH can be variable and basic.
authors.affiliation: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.|Department of Chemistry, Carleton University , Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Guanyong
authors.initials: G
authors.lastname: Su
authors.affiliation: Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University , Ottawa, Ontario K1A 0H3, Canada.|Department of Chemistry, Carleton University , Ottawa, Ontario K1S 5B6, Canada.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Letcher
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University , Nanjing 210023, China.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Yu
mesh_terms: D005411:Flame Retardants; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D010755:Organophosphates; D010968:Plasticizers
chemical_list: D005411:Flame Retardants; D010755:Organophosphates; D010968:Plasticizers