Solvent extraction and spectrophotometric determination of iron(II) with di-2-pyridyl ketone benzoylhydrazone

Abstract

Di-2-pyridyl ketone benzoylhydrazone (DPKBH) was used for the spectrophotometric determination of trace amount of iron(II) in connection with the extraction process. The green iron(II) complex with a maximum absorbance at 379 and 686 nm is quantitatively extracted into benzene from aqueous solution buffered to pH 4.7 – 6.0. Beer's law is obeyed over the range 0–30 μg of iron in 10 ml of benzene at 686 nm. The molar absorptivity of the complex is 1.59 × 10 4 liters mol −1 cm −1. The relative standard deviation for 16.8 μg of iron was 0.48% at this wavelength. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were p K a1 = 3.18 and p K a2 = 10.87 at 25 °C and μ = 0.1.