| Abstract:
In water, methylene blue (MB) is known to be aggregated to dimmer and trimmer at high concentration levels. We conducted a thermodynamic study on the aggregation of MB using multivariate curve resolution analysis of the visible absorbance spectra over a concentration range of 2.0x10-6-4.0x10-4 M. A hard modeling-based multivariate curve resolution method was applied to determine the dissociation constants of the MB aggregates at various temperatures ranging from 25 to 75°C. This method was able to resolve the visible absorbance spectra as a function of MB concentration in individual temperature or simultaneously in all other temperature ranges. Utilizing the van, t Hoff relation, the enthalpy and entropy of the dissociation equilibriums were calculated. For the dissociation of both aggregates, the enthalpy and entropy changes were positive and negative, respectively.
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