Determination of Acid Ionization Constants of 8-Hydroxyquinoline-5-sulfonic Acid by Ultraviolet Spectrophotometry Combined with Multivariate Curve Resolution-alternating Least Squares

A new simple method was developed to determine acid ionization constants of 8-hydroxyquinoline-5-sulfonic acid(8HQS) using spectrophotometry. Spectrum data of 8HQS were collected at different pH and arranged in a data matrix. 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 solution at pH 1. 32~11. 74 were gained through multivariate curve resolution-alternating least squares constrained optimization. The determined acid ionization constants of 8HQS were pK_a1=3. 79,pK_a2=8. 22.