Optimization of a cloud point extraction procedure with response surface methodology for the quantification of iron by means of flame atomic absorption spectrometry

Abstract

A simple micelle-mediated phase separation method has been developed for the pre-concentration of trace levels of iron as a prior step to its determination by flame atomic absorption spectrometry (FAAS). The method is based on the cloud point extraction (CPE) of iron using the non-ionic surfactant poly(ethyleneglycol-mono-p-nonylphenylether) (PONPE 7.5) without the addition of any chelating agent. Several variables affecting the extraction efficiency were studied and optimized utilizing a central composite design (CCD) and a three-level full factorial design. Under the optimum conditions, the limit of detection (LOD), limit of quantification (LOQ) and preconcentration factor were 1.5 μg L-1, 5.0 μg L-1 and 100, respectively. The relative standard deviation (RSD) for six replicate determinations at 50 μg L -1 Fe(III) level was 1.97 %. The calibration graph was linear in the range of 5-100 μg L-1, with a correlation coefficient of 0.9921. The developed method was validated by the analysis of two certified reference materials and applied successfully to the determination of trace amounts of Fe(III) in water and rice samples.