Analytical developments to study diclofenac and some of its transformation products in a contaminated model ecosystem: analysis in bivalve, fish, sediment and watercress
Résumé
Pharmaceuticals are widely found in the aquatic environment, essentially at trace levels, nevertheless long-term exposure can have negative effects on biotic communities due to their intrinsic biological activity. Diclofenac (DCF) is one of the most frequently detected human pharmaceuticals in water and it has lately been included on the “watch” list of the European Union. However little data is available on the detection of this substance and its transformation products in aquatic organisms. In this context, analytical methodologies based either on QuEChERS or on ASE extraction followed by LC-MS/MS analysis were developed to quantify traces of DCF along with nine of its biotic and abiotic transformation products in bivalve, fish, sediment and watercress collected from lotic mesocosm experiments. The analytical protocol was first independently optimized and validated for each matrix of interest: sticklebacks, zebra mussels, sediment and watercress. For the optimization steps, uncontaminated matrices, corresponding to the matrices introduced into the mesocosms before the contamination with DCF were used. Considering the great diversity of transformation products and metabolites, a focus was made in this study on chemically stable and commercially available substances. Next target compounds were measured in samples collected from 6-months mesocosm experiments where DCF was continuously introduced in triplicate channels at three concentrations (5; 0.5 and 0.05 µg/L) and three more channels without DCF were used as control ones. DCF was quantified in zebra mussels and sediment for both highest exposure conditions and in watercress solely for the highest concentration. In sticklebacks DCF resulting concentration was inferior to our quantification limits probably due to rapid depuration as fishes were collected one week after the end of experiments. Among the selected metabolites, 4’OH-DCF was the most often quantified : it was observed in sticklebacks, sediment and watercress for the highest exposure concentration. The metabolites DCF-lactam and 5-OH-DCF were also measured as well as the 2-indolone either in sediment, watercress or bivalves. In this presentation, the optimization of the extraction and clean-up steps will be described. The results of the quantification of DCF, along with nine of its degradation products and metabolites, in organisms and watercress collected from mesocosms will be presented.