Determination of trace amounts of cobalt in alumina by atomic-absorption spectroscopy

Abstract

After the dissolution of alumina by hydrochloric acid in a sealed tube at 270° C traces of cobalt are determined by measurement of atomic absorption at 240·7 nm. In one of the two procedures described cobalt, in the range 50 to 250 p.p.m. in alumina, is determined by aspiration directly into an air-acetylene or nitrous oxide-acetylene flame, and in the other procedure cobalt, in the range 10 to 100 p.p.m. in alumina, is determined by co-precipitation on hydrated manganese dioxide, followed by extraction into isobutyl methyl ketone as its 8-hydroxyquinoline complex. The extract is sprayed into an air-propane flame and absorbance measurements are made as before. No interferences were found from the other elements likely to be present in alumina.

The nitrous oxide-acetylene flame is less favourable than air-acetylene for the determination of cobalt because of the unfavourable effect of the strongly reducing cyanogen zone of the flame and because of considerable loss of atomic cobalt caused by ionisation.