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

Dry soil, fish-fillet ash, and grass ash were dissolved with a closed-vesse l microwave oven system and mineral acids. Reagents and dissolution conditi ons were varied to ensure total dissolution and recovery of radionuclides. Solvents to dissolve 99.9% of the mass of 3 g samples satisfactorily were 4 5 ml 14N HF 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 dissolution was tested with samples from the DOE Qualit y Assurance Program.