Current location: JICS Archive > Vol. 8 > No. 1 > Articles : 16

Application of Multivariate Curve Resolution Analysis for Studying the Thermodynamics of Methylene Blue Aggregations in Aqueous Solutions

B. Hemmateenejad*, G. Absalan and M. Hasanpour

Department of Chemistry, Shiraz University, Shiraz 71457, Iran

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 2.0 × 10^-6-4.0 × 10^-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.

Keywords: Multivariate curve resolution, Methylene blue, Aggregation, Chemometrics, Thermodynamics, Aqueous solution