Loss of zinc and cobalt during dry ashing of biological material

Abstract

Loss of zinc and cobalt during dry ashing of marine mussels (Mytilus edulis) and brown seaweed (Fucus spiralis) has been studied by using material labelled by exposure of living organisms to sea water spiked with zinc-65 or cobalt-60. Even after ashing in porcelain crucibles at temperatures of up to 1000 °C, no significant loss of zinc or cobalt by volatilisation was observed. After ashing at 450 and 550 °C, both radionuclides could be removed quantitatively from the crucibles by leaching with hydrochloric acid. Adsorption on the crucible after ashing at 1000 °C was measured only for cobalt-60. A significant proportion of the cobalt tracer could not be removed from the crucibles by treatment of the latter with acid. From these results it is concluded that dry ashing is a reliable method of sample destruction for the determination of zinc and cobalt in M. edulis and F. spiralis.