title: Aquatic photochemistry of nitrofuran antibiotics.
abstract: The aquatic photochemical degradation of a class of pharmaceuticals known as the nitrofuran antibiotics (furaltadone, furazolidone, and nitrofurantoin) was investigated. Direct photolysis is the dominant photodegradation pathway for these compounds with the formation of a photostationary state between the syn and the anti isomers occurring during the first minutes of photolysis. The direct photolysis rate constant and quantum yield were calculated for each of the three nitrofurans. Reaction rate constants with reactive oxygen species (ROS), 102 and *OH, were also measured, and half-lives were calculated using environmentally relevant ROS concentrations. Half-lives calculated for reaction with 1O2 and *OH are in the ranges of 120-1900 and 74-82 h, respectively. When compared to the direct photolysis half-lives, 0.080-0.44 h in mid-summer at 45 degrees N latitude, it is clear that indirect photochemical processes cannot compete with direct photolysis. The major photodegradation product of the nitrofurans was found to be nitrofuraldehyde, which is also photolabile. Upon photolysis, nitrofuraldehyde produces NO, which is easily oxidized to nitrous acid. The acid produced further catalyzes the photodegradation of the parent nitrofuran antibiotics, leading to autocatalytic behavior. Natural waters were found to buffer the acid formation.
authors.affiliation: Department of Chemistry, University of Minnesota, 207 Pleasant Street Southeast, Minneapolis, Minnesota 55455, USA.
authors.forename: Betsy L
authors.initials: BL
authors.lastname: Edhlund
authors.forename: William A
authors.initials: WA
authors.lastname: Arnold
authors.forename: Kristopher
authors.initials: K
authors.lastname: McNeill
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007700:Kinetics; D009581:Nitrofurans / Q000737:chemistry*; D010777:Photochemistry; D026082:Singlet Oxygen / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D000900:Anti-Bacterial Agents; D009581:Nitrofurans; D014874:Water Pollutants, Chemical; D026082:Singlet Oxygen