Computer simulations of NIR spectra of thymol – Towards linking basic and analytical NIRS

Analytical near-infrared spectroscopy has been evolving rapidly over the last decades reaching a remarkable value for both industrial and institutional laboratories nowadays. Its growth has been strongly connected to focussed development of the instrumentation and multi-variate analytical methods. Multi-variate analysis gives near-infrared spectroscopy the desired analytical performance level but lacks the ability to provide physical insights into the analysed molecular system. Large amount of information carried in an NIR spectrum is omitted in analytical routines. In the present article, we review the latest accomplishments in cross-field research aimed at connecting the basic and analytical near-infrared spectroscopy. An example of thymol molecule, an important constituent of a traditional herbal medicine Thymi herba, is discussed. The key novelty in this case is computer simulation of NIR spectra which allows gaining better understanding of how spectra forming factors correspond to the partial least squares regression coefficients with special attention paid to the role of intermolecular interactions.