title: Degradation of VX surrogate profenofos on surfaces via in situ photo-oxidation.
abstract: Surface degradation of profenofos (PF), a VX nerve gas surrogate, was investigated using in situ photo-oxidation that combines simple instrumentation and ambient gases (O2 and H2O) as a function of exposure conditions ([O3], [OH], UV light λ = 185 and/or 254 nm, relative humidity) and PF film surface density (0.38-3.8 g m(-2)). PF film 0.38 g m(-2) fully degraded after 60 min of exposure to both 254 and 185 nm UV light in humidified air and high ozone. The observed pseudo-first-order surface reaction rate constant (kobs = 0.075 ± 0.004 min(-1)) and calculated hydroxyl concentration near the film surface ([OH]g = (9 ± 2) × 10(7) molecules cm(-3)) were used to determine the second-order rate constant for heterogeneous reaction of PF and OH (k(OH)PF = (5 ± 1) × 10(-12) cm(3) molec(-1) s(-1)). PF degradation in the absence of 185 nm light or without humidity was lower (70% or 90% degradation, respectively). With denser PF films ranging from 2.3 to 3.8 g m(-2), only 80% degradation was achieved until the PF droplet was redissolved in acetonitrile which allowed >95% PF degradation. Surface product analysis indicated limited formation of the nontoxic phosphoric acid ester but the formation of nonvolatile chemicals with increased hydrophilicity and addition of OH.
authors.affiliation: Technion Center of Excellence in Exposure Science and Environmental Health (TCEEH), Technion-Israel Institute of Technology , Haifa, Israel. laurenp@tx.technion.ac.il
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Petrick
authors.forename: Sara
authors.initials: S
authors.lastname: Sabach
authors.forename: Yael
authors.initials: Y
authors.lastname: Dubowski
mesh_terms: D007306:Insecticides / Q000737:chemistry*; D007700:Kinetics; D063086:Organothiophosphates / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D007306:Insecticides; D063086:Organothiophosphates; C024273:profenofos