POST-ADDITION OF SULFURIC-ACID TO WET DIGESTED BIOLOGICAL AND ENVIRONMENTAL MATERIALS FOR MERCURY DETERMINATION BY COLD VAPOR ATOMIC-ABSORPTION SPECTROMETRY

The charring of samples and loss of mercury by a nitric-sulfuric acid mixture has been overcome by prior digestion with nitric acid, followe d by the addition of sulfuric acid into the final solution. This appro ach provides optimum decomposition and analytical conditions for a rel iable cold vapor atomic absorption spectrometric determination of merc ury in biological and environmental materials. In all cases, the prese nce of sulfuric acid improved the sensitivity of the mercury response significantly. Furthermore, the prior-and post-addition of sulfuric ac id gave similar sensitivity and mercury concentrations for all samples . The adequacy of the prior digestion with nitric acid and post-additi on sulfuric acid for reliable mercury determination was successfully d emonstrated for blood, bone, bovine liver, mushroom, lake sediment, pe at and prawn samples.