Behavior of Iodine in Binary Mixtures of Cyclohexane with Dioxane and Tetrahydrofuran Using a Multivariate Curve Resolution Technique

Abstract

The electronic spectra of the iodine molecule in binary mixed solvent systems dioxane–cyclohexane and tetrahydrofuran–cyclohexane were subjected to the multivariate curve–resolution analysis. By using the singular value decomposition method, four different species were identified in the binary mixed solvents. The multivariate curve resolution–alternating least-squares (MCR–ALS) method of Tauler was used to extract the concentration profile and pure spectra of the species present in the mixed solvent systems. Evolving factor analysis was used to obtain the initial estimate of the concentration profiles of the components. The MCR-ALS was implemented by using selected constraints, such as, nonnegativity, unimodality, selectivity, and closure, which are applied during each iteration. Several MCR runs were performed by changing constraints to find the results with lowest fitting error and most chemically reasonable spectra and concentration profiles. From the resulting pure spectra for different iodine species and the corresponding concentration profiles, the nature of iodine species detected in the mixed solvent systems and the influence of the nature of cosolvent have been discussed.