Aqueous solutions of the mixtures of double stranded ribopolyadenylic-polyuridylic acid (rPAU) with 2,2'-bipyridine (bipy) chelates of copper(U) at a constant ion strength (/= 0.15 M) and temperature (37°C), were studied in the medium of varying acidity, with use of UV-absorption spectroscopy and potentiometry. The data obtained revealed changes of the UV-absorption spectra due to the acid-base transformations of the solution components. Using soft modelling chemometric procedures based on factor analysis and multivariate curve resolution, the pure absorption spectra and concentration profiles of all the individual species detected in equilibrium conditions are estimated for the studied systems. The changes of the UV-absorption spectra of mixture solutions depending on the pH, were shown to differ from the ones expected on the ground of an additive model of the balance in the system. Some hindrance in formation of the hydroxobipyridine-copper(II) chelate was found at an increase in the rPAU concentration. The data obtained suggests an influence of the bipyridine-copper(II) upon the rPAU state in a neutral or weakly alkaline solution.