Analytical problems in mercury analysis of seafood.

It is generally accepted that seafood represents one of the major sources of mercury to man. In this work two interlaboratory proficiency tests are described for the analysis of mercury in seafood. Thirty-seven public control and food industries laboratories participated in the first test, while 29 participants were included in the second one. Moreover, in order to clarify whether sampling of different edible muscle tissues of the same fish could affect the analytical results, the top, the central and the bottom portion of 28 fishes were examined. The different portions of fish showed no significant difference in mercury concentrations. Two different wet digestion methods (microwave oven and reflux in quartz vessels) were also tested in the case of 11 fishes. A systematic difference was observed between the two sets of results obtained with these digestion methods.