Dissolution of surfactant mixtures investigated through hyperspectral imaging and multivariate curve resolution

Linear solvent penetration experiments are used to study the dissolution of mixed surfactant pastes consisting of two surfactants and water by means of confocal Raman microscopy. During the experiment, Raman spectra were collected along with space and over time. The resulting hyperspectral data were then processed by means of Multivariate Curve Resolution – Alternating Least Square (MCR-ALS) technique to estimate the evolution of the spatial profile of the surfactant concentrations over time. We show that hyperspectral imaging coupled with MCR-ALS can provide a detailed description of the dissolution process. The experimental concentration profiles are analyzed using a diffusive model with concentration-dependent diffusion coefficient, showing a quantitative agreement. We show that the additional information extracted by confocal Raman microscopy enables a more sophisticated analysis of linear penetration experiments when compared to the traditional approach of surfactant mesophases front propagation tracking even in absence of a detailed phase diagram.