Spectrophotometric Determination of Zn(II) and Cu(II) in ‎Analytical Sample Using Murexide Reagent ‎

The current research aims to develop a new spectrophotometric method for the determination of zinc(II) and copper(II) using a colorimetric reagent, as murexide ion. The complexation of Zn(II) and Cu(II) with murexide has been studied spectrophotometrically at absorption maxima of 450 and 470 nm for Zn-murexide and Cu-murexide, respectively. The murexide reagent interacts with Zn(II) and Cu(II) instantaneously at pH 7 and pH 5.5, respectively, and the absorbance of the solution is stable for 220 and 120 minutes, respectively. Using Job’s continuous variation method, the stoichiometry of the complexes was found to be 1:2 metal to ligand ratio for Zn and Cu, respectively. The continuous variation approach was used to estimate the stability constants (Kstab) values, which were found to be in the order 1.35x1016 and 2.30x107 for Zn and Cu complexes, respectively. The proposed spectrophotometric methodology established that zinc(II) and copper(II) could be estimated at levels of 0.2-2.0 and 0.5-5.0 ppm, which has molar absorptivity values of 1.95x104 and 6.55x103 l.mol-1.cm-1, respectively. Likewise, the formed complexes were stable at different pH values, allowing the simultaneous estimation of the two metals.