Simultaneous spectrophotometric determination of iron species using orthogonal signal correction–generalized partial least squares calibration method after vortex-assisted dispersive liquid–liquid microextraction

Abstract

A vortex-assisted dispersive liquid–liquid microextraction method in combination with UV–Vis spectrophotometry was developed for the simultaneous extraction and determination of iron species. In this method, Fe²⁺ and Fe³⁺ were complexed with pyridine-2-amidoxime, neutralized through ion pair formation with sodium dodecyl sulfate, and extracted into the fine droplets of chloroform. After centrifugation, the absorbance of the extracted complexes was recorded in the wavelength range of 360–700 nm. The parameters affecting the extraction efficiency such as the pH, the type and volume of the extraction solvent, ligand concentration, and sample volume were optimized. The individual iron species was then determined by means of the orthogonal signal correction–generalized partial least squares method. Under the optimized conditions, the calibration curves were linear over the range of 2.0–100 and 3.0–200 µg L⁻¹ with detection limits of 0.4 µg L⁻¹ for Fe²⁺ and 0.8 µg L⁻¹ for Fe³⁺, respectively. The relative standard deviations for intra- and inter-day assays (n = 5) were 2.3 and 4.0 for Fe²⁺ at 50 µg L⁻¹ and 2.7 and 4.3 for Fe³⁺ at 30 µg L⁻¹, respectively. The enhancement factors of 77 and 69 were achieved for Fe²⁺ and Fe³⁺, respectively. The proposed method was successfully applied to the determination of iron species in water samples.