The 2650 cm -1 to 3900 cm -1 wavenumber data (the region that contains the O-H stretching signal) was selected from the measured spectra. A linear baseline connecting the points at the two extreme ends was subtracted from the spectra. This led to small negative values, instead of perfect zeroes, at the edges, due to experimental noise. An intensity offset was applied to the spectra to make the minimum intensity in each of them, a very small positive value ). Following the established convention for pre-processing of spectra for MCR studies, the spectra were all normalised to unit area, in order to account for possible intensity variations from one measurement to another due to external factors such as laser power fluctuation or optical alignment variations.