Separation, preconcentration and measurement of inorganic iron species by cloud point extraction and flow injection flame atomic absorption spectrometry

Abstract

A sensitive and simple method for determination of iron species after separation/preconcentration by cloud point extraction (CPE) has been developed. When the temperature is higher than the cloud point extraction temperature (60 °C), the complexes of iron(II) and iron(III) species with ferron enter the surfactant-rich phase. Total amount of iron in the surfactant-rich phase was analyzed by FI-AAS, whereas, Fe(II) concentration was determined by a spectrophotometric method using mathematical equation to overcome the interference of Fe(III), when they are both present in the same solution. In this way the time-consuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) were eliminated. The parameters affecting could point extraction, such as concentrations of ferron and Triton X-114, pH, and equilibrium temperature were systematically investigated. Under the optimum conditions, the calibration curves were linear over the range of 10-250 and 5-150 μg l^-1 for 20 and 40 ml preconcentration volume, respectively. The detection limit was 1.7 μg l^-1, and relative standard deviation (RSD) was 2.1% for 20 ml preconcentration volume. The method was applied to the determination of iron species in water samples and total iron in milk. The accuracy was determined by recovery experiment, independent analysis by furnace atomic absorption spectrometry and analysis of certified reference water.