Resolution of overlapping UV-visible absorption bands: Quantitative analysis of tautomeric equilibria

A quantitative approach for the analysis of two-component mixtures with unknown spectra of the pure components, based on resolution of the UV-visible absorption spectra into individual bands is proposed and its reliability is confirmed. The proposed method is applied for the analysis of the tautomeric equilibrium of 1-phenylazo-4-naphthol. The molar parts and individual spectra of both tautomeric forms and tautomeric constant Kt are determined. The proposed general approach could be applied for quantitative analysis of any other two-component equilibria including aggregation, acid-base processes, complex formation, where the absorption spectra of the individual forms cannot be obtained experimentally.