Chemical modifiers for controlling interferences in the flame atomic absorption spectrometric determination of chromium(III) and chromium(VI) and their separation

Abstract

The interfering effects of a range of organic and inorganic species on the atomic absorption signals of Cr^III and Cr^VI were investigated. Such effects were eliminated by adding 20 mmol l^–1 butylamine (BA) or N-cyanoacylacetaldehyde hydrazone (CyAH), as a chemical modifier, to both the sample and standard solutions. The role of BA was extended to separate Cr^III from Cr^VI in admixture, with 100% recovery, using oleic acid as a surfactant at a pH of 5.5 ± 0.2. A mechanism for Cr atom population in the flame in the presence and absence of concomitants is suggested. Also, the role of BA or CyAH in eliminating interferences was investigated. The flotation mechanism is discussed. A simple, sensitive and rapid procedure for the separation and determination of Cr^III from aqueous solutions was elaborated. The method was applied to the determination of Cr^III in some complexes.