FTIR-ATR of aqueous β-alanine: pH effect and molecular dissociation

In this work, we present detailed analysis of the dissociation of β-alanine solutions over the pH range of 1.54 to 12.52 using the Fourier transform infrared attenuated total reflection (FTIR-ATR) technique combined with Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) methods. By applying appropriate spectrum subtraction methods, we obtained FTIR-ATR spectra of the solvated β-alanine as a function of pH. Discernible changes were identified in the absorption region between 1 800 and 1 000 cm-1. The number of components was calculated using singular value decomposition and evolving factor analysis in the complex system.The concentration profiles and the pure spectrum of three species in aqueous solutions in the pH ranging from 1.54 to 12.52 were gained through MCR-ALS constrained optimization. The effect of aqueous solution environment was also investigated in terms of 200 mmol·L-1 NaCl. The dissociation constants of β-alanine in aqueous solutions and NaCl solutions were also determined.