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Determination of stoichiometry and stability constants of iron complexes of phenanthroline, Tris(2-pyridyl)-s-triazine, and salicylate using a digital camera

Ahmed A. Shalaby and Ashraf A. Mohamed

Department of Chemistry, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt



Received: 28 January 2020  Accepted: 7 May 2020


The determination of stoichiometric ratios and stability constants of metal–ligand complexes is of great importance for physical, chemical, biochemical, and environmental studies and often require relatively expensive and sophisticated instruments. Herein, we introduce a simple, accurate, and low-cost method for determining these parameters by a conventional digital camera. The stoichiometric ratios and stability constants of iron complexes of 1,10-phenanthroline, 2,4,6-Tris(2-pyridyl)-s-triazine, and salicylate were determined, as model examples, using the molar ratio and the continuous variation methods. Digital images of solutions with various metal–ligand ratios were captured and analyzed, and the Yxy color absorbance and the ΔELUV color difference parameters were used as convenient analytical signals that favorably compete with conventional spectrophotometric signals. For the three studied iron complexes, the results of stoichiometric ratios and stability constants obtained from digital images were in excellent agreement with the spectrophotometric and the previously reported literature’s data.

Keywords: Digital imaging; Yxycolor absorbance; ΔELUV color difference; Stability constant; Metal complexes; Absorption spectra

Full paper is available at

DOI: 10.1007/s11696-020-01192-4


Chemical Papers 74 (10) 3589–3595 (2020)

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