Determination of total mercury in fish tissues using combustion atomic absorption spectrometry with gold amalgamation

A simple and rapid procedure for measuring total mercury in fish tissues is evaluated and compared with conventional techniques. Using an automated instrument incorporating combustion, preconcentration by amalgamation with gold, and atomic absorption spectrometry (AAS), milligram quantities of wet fish tissue were analyzed directly for mercury (i.e., without acid digestion). Seven tissue types (skeletal muscle, liver, blood, gonad, brain, gill, and heart) from five species (340 fish) were analyzed. Because of the small quantities of tissue needed for analysis, we document the homogeneity of mercury within the tissues and determine a preferred sampling technique and location for skeletal muscle. The precision was found to be generally > 10% (rsd), and the accuracy was determined by using certified reference materials (dogfish muscle, dogfish liver, and oyster tissue). Comparisons to conventional cold-vapor AAS (CV-AAS) and isotope dilution inductively coupled plasma mass spectrometry found that the methods give statistically equivalent (p > 0.05) results. Because the combustion-AAS method is faster than conventional CV-AAS and produces no waste reagents, it should be particularly useful for laboratories that analyze large numbers of fish for mercury. The method detection limit for fish-muscle homogenate was estimated at 0.9 ng g(-1).