Flame atomic absorption spectrometric investigation and determination of cobalt and copper using ethanolamine and triethanolamine as chemical modifiers

Abstract

In the flame atomic absorption spectrometric investigation and determination of cobalt and copper, serious interfering effects were observed from borate and silicate on cobalt whereas borate, iron, indium and iridium interfered on copper. Enhancement, depression and absence of interferences were observed from a range of organic species on both cobalt and copper. All of these effects were attributed to chemical interferences as a result of their occurrence at different flame profiles to various extents. Ethanolamine (EA) and triethanolamine (TEA) were found to be effective chemical modifiers for complete elimination of the interferences encountered from the foreign species studied separately or in combination on cobalt and copper, respectively. The role of EA and TEA in eliminating the interfering effects originates from the solution for TEA whereas EA exerts its effect at the base of the burner where complexation with cobalt takes place by heating. In the reaction zone, an equilibrium for the decomposition of EA–Co or TEA–Cu species is established, yielding a consistent number of free cobalt and copper atoms. The excess amount of the modifier decomposes in the reaction zone, creating a reducing medium, which shifts the equilibrium in favour of analyte atomization. A procedure is proposed for the determination of cobalt or copper in some of their complexes.