Effect of selenium on determination of mercury in animal tissues

Selenium in animal tissues was found to influence the reactivity of mercury in the tissues with stannous chloride or with stannous chloride plus cadmium chloride added as reducing agents for the determination of mercury by the method developed by L. Magos (1971, Analyst, 96, 847-853) and L. Magos and T. W. Clarkson (1972, J. Assoc. Offic. Anal. Chem., 55, 966-971). The recovery of mercury in the tissues of animals to which inorganic mercury and selenite were simultaneously administered was low compared to the case in which inorganic mercury alone was administered. Of the in vitro interactions of inorganic mercury and selenite examined in tissue homogenates and blood samples, only those interactions in blood samples caused the difficulty in mercury analysis mentioned above, i.e., there was a marked decrease in recovery of mercury when an equimolar amount of each compound was added to the blood. These facts suggest that selenium and inorganic mercury in the animal tissues are likely to interact with each other and might form a chemically stable state of inorganic mercury which resists reduction with stannous chloride in the procedure for mercury determination.