Evaluation of the bioaccumulation of trace elements in tuna species by correlation analysis between their concentrations in muscle and first dorsal spine using microwave-assisted digestion and ICP-MS

Environmental pollution by metals is a recognized problem worldwide. As a result of the exposure to this pollution, marine species may bioaccumulate metals in both muscle and fishbone, as has been demonstrated in some species of tuna. The objective of this study has been the development and optimization of an inductively coupled plasma-mass spectrometry (ICP-MS) based method, which allows the quantification of 21 elements including priority pollutants and biologically essential elements (B, Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Pd, Cd, Ba, La, Hg and Pb) in muscle and in the first spine of the first dorsal fin of albacore (Thunnus alalunga) and bluefin tuna (Thunnus thynnus). A microwave-assisted digestion has been developed for sample treatment, which has been evaluated using isotope dilution analysis (IDA) of Cr, Se, Cd, Ba and Pb. Evaluation of the analytical method in terms of sensitivity (LOQ between 0.002 and 1 mg kg(-1)), accuracy and precision within and between days (CV < 11.3%) has also been conducted. The developed method has allowed information to be obtained on levels of these metals in both matrices. The correlation analyses performed for each of the metals in both matrices shows a positive linear relationship between the concentrations in muscle and fishbone for Zn, Se, Rb, Cd, As and Hg, which could be due to a higher bioaccumulation of these elements in muscle as it is concluded from the low spine/muscle ratios observed for these elements. The 34 specimens of tuna analyzed show that while the levels of Pb, Cd, Ni, Zn, Cu and Cr in muscle are below the limits set by the WHO/FAO, EC and the US-EPA, Hg shows higher concentration than the limits set by the EC in four samples, indicating a potential risk to human health.