Fate of the drug chlorpromazine in river water according to laboratory assays. Identification and evolution over time of degradation products. Sorption to sediment

Abstract

Toxic effects of the non-biodegradable drug chlorpromazine and its degradation products have been reported on microorganisms in aqueous media. Here, chlorpromazine degradation assays in forced and non-forced conditions have been done to know its persistence and degradation products in river water. Sunlight irradiation promotes the complete degradation of chlorpromazine (2 μg L−1) in less than 4 h, but if the exposure to sunlight is limited chlorpromazine is detected during 4 weeks in river water. Sixteen degradation products in surface water are described for first time after solid-phase extraction and analysis by ultra-pressure liquid chromatography/quadrupole time-of-flight/mass spectrometry; their structures are proposed from the molecular formulae of the fragment-ions observed in high-resolution tandem mass spectra. Hydroxylation and oxidation products such as chlorpromazine sulfoxide, 2-hydroxypromazine and 2-hydroxypromazine sulfoxide were predominant degradation products in the early stages; some benzo[1,4]thiazin-6-ol derivatives resulting from the breakdown of the phenothiazine core were the major and relatively stable products after 20 weeks under non-forced conditions. A degradation pathway of chlorpromazine in water is outlined. Moreover, it is shown that chlorpromazine is very strongly adsorbed on sediment while the degradation products that kept the promazine core have a notable capacity of sorption, too; sorption coefficients are calculated. Finally, a prediction about the toxicity of the degradation products in aquatic ecosystems suggests that some of them have toxicities similar, or even higher, than chlorpromazine.