Structure of hexafluoroisopropanol–water mixture studied by FTIR-ATR spectra and selected chemometric methods

The FTIR spectra of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)–water binary solutions have been obtained by means of attenuated total internal reflection (ATR) spectroscopy. The spectral properties of the system have been analyzed as a function of alcohol concentration by following methods: multivariate curve resolution based on alternating least-square procedure (MCR-ALS) preceded by evolving factor analysis (EFA), kernel analysis, and two-dimensional (2D) correlation spectroscopy. From all the information obtained by these methods the four-component model describing the aggregation of HFIP and water molecules in HFIP–water mixtures was proposed. In characterization of properties of the components not only changes in the aggregation process were taken into account but also variations in relative population of different HFIP conformations were considered. The case reported is a very good example to show how the MCR-ALS and 2D analysis could complement each other, leading to enhancement of the multicomponent data interpretation.