Abstract
Formation of the metal complexes of aspartic acid (Asp) with the chromium metal ion (Cr3+) in solutions using potentiometric titrations is presented within a wide pH range (∼3.5 to ∼10.5) at 25°C and I=0.10 M NaNO3. Concentration distribution diagrams revealed that the main complex formed within this pH range is the bis Cr 3+ complex. Literature stability constant values for the Cr–Asp complexes were used to construct concentration distribution diagrams. Complexes taken into consideration were the simple one-to-one complex, the bis-complex, and the bis-mono-protonated complex, namely, Cr–Asp, Cr(Asp)2, and Cr(Asp)2H. The corresponding Log β values of these complexes were 12.46, 21.86, and 24.30, respectively. UV–Vis spectra demonstrate Cr 3+–Asp binding. The UV–Vis spectra were collected from a system that reached a high level of equilibrium state (50 days’ equilibrium time).
Acknowledgement
Special thanks go to Dr Ted Burkey of the University of Memphis for helpful comments.
Funding
This work was supported by the NSF [grant number HRD-1332459] and the American Chemical Society SEED program.
Supplemental data
Supplemental data for this article can be accessed at 10.1080/2164232X.2014.883291.