Near-infrared (NIR) spectroscopy can capture the information of both isolated molecules and the inter- or intra-molecular interactions, and the spectral variation induced by temperature can be reflected in the temperature-dependent NIR spectra. Meanwhile, NIR spectroscopy is a powerful tool for obtaining the spectral information of OH groups, and the temperature has a significant effect on the hydrogen bonds. All these features make the technique a powerful tool for analyzing the content and structure in complex systems, particularly for the aqueous solution and bio-systems. Due to the complexity of the spectra, however, chemometric methods must be adopted for analyzing the temperature-dependent NIR spectra. In our works, the quantitative spectra–temperature relationship (QSTR) models were established for the mixtures of water, methanol, ethanol and ethylenediamine. Quantitative analysis of the composition in mixtures was achieved based on the difference between QSTR models of different mixtures. Moreover, multilevel simultaneous component analysis (MSCA) was applied for establishing the QSTR and quantitative models using temperature-dependent NIR spectra. A new method named as mutual factor analysis (MFA) was proposed for extracting the common spectral features contained in the spectra of different temperature or different concentration, and the relative quantity of the extracted spectral features was proportional to the temperature or concentration. On the other hand, chemometric methods can also be used to extract structural information from temperature-dependent NIR spectra. Gaussian fitting was employed to separate spectral features of water species of different hydrogen bonding from the spectra of glucose solutions. High order chemometric algorithms were applied for analyzing the formation of water-ethanol hetero-cluster using the temperature-dependent NIR spectra of water-ethanol mixtures. Moreover, independent component analysis and two-dimensional correlation analysis were used for studying the transition of protein conformation by the temperature dependent NIR spectra.

Temperature-dependent near-infrared spectroscopy for analyzing aqueous samples

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.