Identification of ultraviolet transformation products of diclofenac by means of liquid chromatography and mass spectrometry.

The removal of the anti-inflammatory drug diclofenac, which can be determined in concentrations up to 1μg/mL in the aquatic environment, from water samples by the use of UV light is investigated by liquid chromatography/mass spectrometry (LC/MS). It is very important to find out whether diclofenac is fully mineralized into non-toxic products or if the UV treatment leads to other potentially bioactive products. The irradiation of an aqueous solution of diclofenac with light in the wavelength range of 220nm-500nm provides a fast degradation of diclofenac in less than four minutes. Eleven transformation products have been detected by means of reversed-phase LC/MS, seven of which have not been described in literature before. Fragmentation experiments allowed their characterization and lead to proposed structures for most of them. Some of the structures may explain the increased toxicity, which was observed after irradiation of diclofenac solution by other groups.