Preconcentration extractive separation, speciation and spectrometric determination of iron(III) in environmental samples

Preconcentration, speciation and separation with solvent extraction of Fe(III) from samples of different origin, using methyl isobutyl ketone (MIBK) as a solvent and the sodium salt of 2-carboethoxy-1,3-indandione (CEIDNa) as a complexing agent for Fe(III), were studied. CEIDNa reacts with Fe(III) in the pH range 1.5-3.5 to produce a red colored complex of Fe(III)-CEIDNa (1:3 molar ratio) soluble in MIBK. The investigation includes a study of the characteristics that are essential for solvent extraction, spectrophotometric and flame atomic absorption spectrometric determination (AAS) of iron. A highly sensitive, selective and rapid spectrometric method is described for the trace analysis of iron(III) by CEIDNa. The complex formed obeys Beer's law from 0.06 to 1.8 mg l(-1) with an optimum range. A single step extraction was efficiently used with a distribution ratio (D) = 10(3.6). The extracted red colored (1:3) Fe-CEIDNa was measured spectrophotometrically at 500 nm with a molar absorptivity of 1.2 x 10(4) l mol(-1) cm(-1). In addition, the organic phase was directly aspirated to the flame for AAS determination and the signals related to Fe(HI) concentration were recorded at 243.3 nm. The complexation of iron(III) with CEIDNa allows the separation of the analyte from alkali, alkaline earth and other elements, which are not complexed. The proposed preconcentration procedure was applied successfully to the determination of trace Fe(III) in soil, milk and natural water samples. (C) 2003 Elsevier B.V. All rights reserved.