Determination of trace metals in fish species of the Ria de Aveiro (Portugal) by electrothermal atomic absorption spectrometry

Cadmium, copper, nickel, lead and zinc were determined in fish samples from seven sampling stations of the Ria de Aveiro (Portugal). The species analyzed were Anguilla anguilla, Mullus surmuletus, Trigla lucerna, Mugil cephalus, Chelon labrosus, Liza aurata and Dicentrarchus labrax, all of which are used for human consumption. For this purpose, procedures for the electrothermal atomic absorption spectrometry determination of cadmium, copper, nickel and lead in these samples were developed, as well as a microwave digestion method for obtaining a fast dissolution of the samples. The concentrations of metals found in the muscle of the fish species were very low. The minor contents corresponded to cadium, lead and nickel with values smaller than 0.043, 0.15 and 0.14 μg/g (wet weight), respectively, except in the case of nickel in the Anguilla anguilla species where more elevated concentrations were found (between 0.16 and 0.40 μg/g). The contents of copper in the samples ranged from 0.5 to 1.1 μg/g (wet wt.). Zn is the most abundant element in all fishes, with concentrations around 20 μg/g (wet wt.) in the Anguilla anguilla samples and with values oscillating between 4.7 and 12 μg/g in the rest of the species studied. In all cases, the results obtained for all the elements were considerably lower than those recommended by specific legislation for these aquatic organisms. The accuracy of the analytical methodology employed was also evaluated through the analysis of two reference materials (NIST-1577b and IAEA-V10): good agreement was obtained between the experimental results and the certified values.