Total dissolution of environmental and biological samples by closed-vessel microwave digestion for radiometric analysis

Abstract

Dry soil, fish-fillet ash, and grass ash were dissolved with a closed-vesselmicrowave oven system and mineral acids. Reagents and dissolution conditionswere varied to ensure total dissolution and recovery of radionuclides. Solventsto dissolve 99.9% of the mass of 3 g samples satisfactorily were 45 ml 14NHF followed by 60 ml 4N HNO₃ saturated with H₃BO₃ for soil, 60 ml 9N HNO₃ followed by 60 ml 14N HF for grass,and 60 ml 9N HNO₃ for fish. The reliability of the dissolutionwas tested with samples from the DOE Quality Assurance Program.