Analysis of Equilibrium and Kinetics of Chromium-Fluoride Complexation from Spectroscopic Data via Chemometrics Methods

摘要

The complexation of Cr~(3+) with F~- undergoes a multistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L( metal to ligand) and 50℃, the result of Principal Component Analysis(PCA) shows that three complexes, ML, ML_2 and ML_3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis(TTFA). Meanwhile, a reactive intermediate was observed before the formation of ML_x during the specific kinetic study at 15℃. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.