Occurrence of diclofenac and its metabolites in surface water and effluent samples from Karachi, Pakistan

Diclofenac and five of its transformation products were identified in Malir River and Lyari River water as well as in effluent samples from Karachi, Pakistan. To the best of our knowledge, this is the first report on the identification of 3′-hydroxydiclofenac and 8-chlorocarbazole-1-yl-ethanoic acid in environmental samples. Their estimated concentrations ranged between 0.08–0.3 μg L−1 and 0.03–0.4 μg L−1, respectively. In addition, 4′- and 5-hydroxydiclofenac as well as 1-(2,6-dichlorophenyl)-1,3-dihydro-2H-indole-2-one were detected in the samples at concentrations between 0.4–1.8, 0.01–0.3, and 0.02–0.2 μg L−1, respectively. The hydroxy derivatives seem to reflect human excretions via household wastewater, while the chlorocarbazole derivative is related to abiotic photolytic transformation of diclofenac.