Khaled Elsherif - Chemistry Department, Faculty of Science, University of Benghazi, Benghazi, Libya
Qamar Hadidan - Chemistry Department, Faculty of Arts and Science, Elmergib University, Al-khoms, Libya
khawla Alkariwi - Chemistry Department, Faculty of Arts and Science, Elmergib University, Al-khoms, Libya

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 ۴۵۰ and ۴۷۰ nm for Zn-murexide and Cu-murexide, respectively. The murexide reagent interacts with Zn(II) and Cu(II) instantaneously at pH ۷ and pH ۵.۵, respectively, and the absorbance of the solution is stable for ۲۲۰ and ۱۲۰ minutes, respectively. Using Job’s continuous variation method, the stoichiometry of the complexes was found to be ۱:۲ 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 ۱.۳۵x۱۰۱۶ and ۲.۳۰x۱۰۷ for Zn and Cu complexes, respectively. The proposed spectrophotometric methodology established that zinc(II) and copper(II) could be estimated at levels of ۰.۲-۲.۰ and ۰.۵-۵.۰ ppm, which has molar absorptivity values of ۱.۹۵x۱۰۴ and ۶.۵۵x۱۰۳ l.mol-۱.cm-۱, respectively. Likewise, the formed complexes were stable at different pH values, allowing the simultaneous estimation of the two metals.

Spectrophotometric methods, Murexide, zinc, copper, stability constant