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

Abstract

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 °C, 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, during the specific kinetic study at 15 °C. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.