Near-infrared spectral studies of hydrogen-bond in water-methanol mixtures

Investigations of hydrogen bond in a water-alcohol mixture were carried out with the near-infrared (NIR) spectra of water-methanol solutions over a concentration range of 0-100 wt% with an interval of 5 wt% by analyzing the concentration-dependent variations of OH bands due to combination and overtone modes. Since the OH bands strongly overlapped in the NIR region, various spectral analysis methods, such as second derivatives, principal component analysis (PCA), and two-dimensional (2D) correlation analysis, were employed to improve the spectral resolutions and obtain the effective information from the NIR spectra of water-methanol mixtures. The possible combined modes between water and alcohol in the system of water-alcohol mixture were qualitatively described. The present study provides a new possibility for investigating the hydrogen bond in water-alcohol mixtures.