EVALUATION OF SOME WET DECOMPOSITION METHODS FOR MERCURY DETERMINATION IN BIOLOGICAL AND ENVIRONMENTAL MATERIALS BY COLD VAPOR ATOMIC-ABSORPTION SPECTROSCOPY

Four of the most commonly used wet digestion methods were evaluated fo r the accurate determination of mercury in biological and environmenta l materials by cold vapour atomic absorption spectroscopy. The method based on the use of HNO3-H2SO4 mixture was found to be most suitable f or the reliable determination of the element. The recovery efficiencie s of the method for mercury in fish homogenate and horse kidney sample s were 95.9 and 105.7%, respectively for the inorganic form, and 89.0 and 99.8% for the organic form. The method based on the use of HNO3-H2 O2 mixture also gave similar recoveries for the organic and inorganic mercury in these samples. In comparison, the recoveries of the organic mercury in the fish and kidney samples by the use of HNO3 only and HN O3-HClO4 mixture were < 50%, but their recovery efficiencies for the i norganic mercury were close to 100%. The application of the method uti lizing the HNO3-H2SO4 mixture to a range of biological and environment al standard reference materials gave the most accurate and reproducibl e analytical data. The suitability of the digestion method for the rel iable determination of mercury in soil samples was also demonstrated.