Simultaneous determination of ferric, ferrous and total iron by extraction differential pulse polarography: application to the speciation of iron in rocks

The voltammetric characteristics of Fe(III) oxinate at a mercury electrode, in the presence of 0.2 M tributylammonium perchlorate (tri-BAP) and 0.2 M tributylamine (tri-BA) as the supporting electrolyte have been studied in chloroform. With this supporting electrolyte a two electron quasi-reversible process for the reduction of Fe(III) oxinate was observed. Preceded by a solvent extraction of Fe(III) oxinate in chloroform, differential pulse polarography (DP) was used for the determination of iron. The calibration graph was linear over the concentration range 0.5-50 muM Fe(III) oxinate in chloroform and the detection limit was 1.5 muM. The proposed DP method has been used for the determination of ferric, ferrous and total iron in a mixture and successfully applied to the speciation of iron in rocks. (C) 2000 Elsevier Science B.V. All rights reserved.