Photochemical Fate of Sulfa Drugs in the Aquatic Environment:  Sulfa Drugs Containing Five-Membered Heterocyclic Groups

The photochemical fate of five sulfa drugs with varying five-membered heterocyclic substituents (sulfamethoxazole, sulfisoxazole, sulfamethizole, sulfathiazole, and sulfamoxole) was investigated in aqueous solution. The rate of direct photolysis of these compounds is dependent upon the identity of the heterocyclic R group as well as the pH of the solution. Matrix deconvolution methods were employed to determine the absorption spectrum and photolysis rate of each protonation state (cationic, neutral, and anionic). From these data, quantum yields for direct photodegradation were calculated for each protonation state of the sulfa drugs. The quantum yields calculated range from

• UO
  University of Minnesota
• NI
  National Institutes for Water Resources
• UG
  U.S. Geological Survey