Environmental photodegradation of mefenamic acid

Jeffrey J. Werner, Kristopher McNeill, William A. Arnold

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


Pharmaceuticals and personal care products are an emerging class of environmental pollutants. Photolysis is expected to be a major loss process for many of these compounds in surface waters, including the common non-steroidal anti-inflammatory drug mefenamic acid. The direct photolysis solar quantum yield of mefenamic acid was observed to be 1.5 ± 0.3 × 10-4. Significant photosensitization was observed in solutions of Suwanee River fulvic acid and Mississippi River water, as well as for the model photosensitization compounds 3′-methoxyacetophenone, 2-acetonaphthone and perinaphthenone. Quenching, sparging and light-filtering experiments suggested a direct reaction of mefenamic acid with excited triplet-state dissolved organic matter as the major photosensitization process. The persistence of the model photosensitizer suggests that the photosensitization by perinaphthenone occurs either by triplet-energy transfer or an electron transfer followed by rapid regeneration of the sensitizer. Due to its low quantum yield, the loss of mefenamic acid in sunlit natural waters is expected to depend on both direct and indirect photodegradation processes.

Original languageEnglish (US)
Pages (from-to)1339-1346
Number of pages8
Issue number10
StatePublished - Mar 2005

Bibliographical note

Funding Information:
The authors wish to thank the National Institute for Water Resources/USGS National Water Quality Competitive Grant Program and the University of Minnesota Center for Urban and Regional Affairs for the financial support of this work.

Copyright 2008 Elsevier B.V., All rights reserved.


  • Dissolved organic matter
  • Pharmaceutical
  • Photolysis
  • Quantum yield
  • Triplet


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