Studies in the ratio total mercury/methylmercury in the aquatic food chain†

Abstract

A rapid and extremely sensitive method for the separation of inorganic mercury (Hg) from methylmercury (MeHg) and the simultaneous determination of both compounds by CVAAS has been developed. The determination limit of the total procedure for MeHg is approximately 0.2 μg/kg for solids, 0.1 μg/kg for biological fluids like blood and urine, and 0.2 ng/kg for aqueous samples. The determination of inorganic Hg and MeHg of some links of the aquatic food chain according to this method resulted in high percentages of inorganic Hg (84.7–85.7% of total Hg) and low percentages of MeHg (14.3–15.3% of total Hg) for algae. While already mussels show lower percentages of inorganic Hg (44.4–79.9% of total Hg) but higher percentages of MeHg (20.1–55.0% of total Hg), all fish samples yield by far the lowest percentages of inorganic Hg (1–26.0% of total Hg) and as expected the highest percentages of MeHg (73.1–99% of total Hg). The ratio MeHg/total Hg found in fish even in fish of different species is approximately constant.