Simultaneous determination of mercury and butyltin species using a multiple species-specific isotope dilution methodology on the European, Anguilla anguilla glass eel and yellow eel

A methodology to simultaneously determine mercury (MeHg, IHg) and butyltin (TBT, DBT, MBT) compounds in eel samples was assessed and validated using multiple isotopically enriched species. The developed methodology was able to analyse simultaneously the organometal species accurately and precisely and to correct for the potential transformations/degradations of the different species during the various steps of the analytical procedure. Low detection limits were achieved (0.007–0.17 µg Hg kg⁻¹ for mercury (Hg) species and 0.42–0.71 µg Sn kg⁻¹ for tin (Sn) species) allowing analysis of low-mass samples and thus the analysis at the individual organism scale, including glass eels for which samples dry weight ranged from 60 to 100 mg. The methodology was validated with certified reference materials (BCR-464, BCR-477, BCR-710, DOLT-4 and NIST-2977) and applied to the analysis of these pollutants in two developmental stages of the European eel, Anguilla anguilla: individual whole glass eels and muscle tissue from yellow eels. The Adour estuary (South-west France) was selected to monitor the bioaccumulation of organometal species in these organisms, according their developmental stage, their morphological parameters and the sampling site. The results suggest that the accumulation of methylmercury in glass eel tissue is related to weight, with higher concentrations in smaller individuals. Butyltin concentrations were very close to the limit of detection, and no significant differences were detected between glass and yellow eels.