The determination of chromic oxide in faeces samples by atomic absorption spectrophotometry

A rapid and accurate atomic absorption method for the determination of chromium in faeces samples from pasture experiments using chromic oxide ‘markers’ is described. Of the elements present after ashing and digesting the samples in a phosphoric acid—manganese sulphate—potassium bromate solution silicate, aluminium, calcium and magnesium were found to interfere in the determination. The effects of these interferences were overcome by the addition of calcium to the test solution and by the addition of silicate to the standards, which were prepared in ‘blank’ solutions. The sensitivities of a number of alternate chromium resonance lines relative to that of Cr 3578·7 Å. are given. These lines may be used to increase the concentration range of the analysis. The results of a comparison of the atomic absorption method with a chemical method are given.