The effect of valency state on the determination of chromium in perchloric acid media by atomic-absorption spectrophotometry

Abstract

Measurements of the atomic absorption of chromium, present in perchloric acid solutions in both the chromium(III) and chromium(VI) states, show that the valency state of the chromium is important. Conversion of all of the chromium into the chromium(III) state by the addition of hydrogen peroxide overcomes this valency problem and also ensures that the maximum absorption is obtained for a given concentration of chromium.

Comparison of the atomic-absorption results obtained by using the air-acetylene and nitrous oxide-acetylene flames, with and without the addition of ammonium chloride, shows that the choice of these parameters has appreciable effects. Up to a 30 per cent. higher chromium response has been found to occur with the addition of ammonium chloride and a further 30 per cent. increase can be obtained by the use of the nitrous oxide-acetylene flame.