Simultaneous Determination of Copper and Iron in Biological Samples with 1-(2-Pyridylazo)-2-naphthol in Anionic AOT Micellar Solution Using Derivative Spectrophotometry

Abstract

A simple and selective derivative spectrophotometric method using 1-(2-pyridylazo)-2-naphthol (PAN) in bis-2-ethyl hexyl sulfosuccinate (AOT) micellar solution was developed for determination of copper and iron. The effect of various parameters on the sensitivity and selectivity of the method was investigated and optimum conditions were selected. The pH = 2.5 was chosen as an optimum in order to reduce the interference effects. At this pH, in addition to Cu(II) and Fe(III), only Ni(II), Co(II) and Co(III) may be react with PAN and interfere the determination of copper and iron. The concentrations of nickel and cobalt in the most samples usually are very low and thus have no interference on the determination of copper and iron. In the presence of AOT the absorption spectrum of Fe(III)-PAN complex shift to higher wavelengths and the overlapping with Cu-PAN spectrum was decreased. In this condition, in ordinary spectrophotometry, Cu(II) has no interference in the determination of iron, but Fe(III) completely interfere the determination of copper. In the first order derivative mode the spectra of Cu(II)-PAN and Fe(III)-PAN complexes completely resolved together and selectively can determine them. The zero and first order derivative spectrophotometric calibration curves were drawn at working wavelengths of 558 and 580 nm for copper and 600 and 630 nm for iron. Molar absorbtivity were found 1.82 × 10⁴ and 2.75 × 104 L mol^-1 cm^-1, respectively for Cu(II)-PAN and Fe(III)-PAN complexes. In derivative mode, the limits of detection (LOD) for Cu(II) and Fe(III) were 0.038 and 0.025 μg mL^-1, respectively. The method has been applied to human hair and serum samples successfully.