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Application of chemometrics methods in thermodynamics investigation of the dimerization equilibria of nile blue in different concentration by spectral titration

M.Mazloum Ardakani, J.Ghasemi, S.Lotfei, M.Noroozi

`The monomer-dimer equilibrium of Nile blue (NB) dye has been investigated by UV-Vis spectroscopy. The dimerization constants of Nile blue have been determined by studying of the dependence of their absorption spectra on the temperature in the range 20-800C at different total concentrations of dye (8.5ï‚´10-5 to 3ï‚´10-4M). The equilibriumparameters of the dimerization of Nile blue have been determined by chemometrics refinement of the absorption spectra obtained from thermometric titrations at different concentrations. The quantitative analysis of the data of undefined mixtures, was carried out by simultaneous resolution of the overlapping spectral bands in the whole set of absorption spectra. Utilizing the vanÂ’t Hoff relation, which describes the dependence of the equilibrium constant on temperature, as constraint,we determine the spectral responses of themonomer and dimer species as well as the enthalpy and entropy of the dimerization equilibrium.