Two-dimensional (2D) band shift correlation spectroscopy for near-infrared (NIR) imaging data

Two-dimensional (2D) correlation technique was applied to near-infrared (NIR) imaging data analysis of cellulose tablets under varying grinding time. A substantial level of band position shifts were observed when the grinding was applied to the cellulose samples. It was shown that fine features of the band position shifts could be readily analyzed by the 2D correlation scheme. Namely, a perturbation-induced variation of the observed peak position, instead of intensity, was utilized as a spectral index. The 2D NIR band shift correlation indicates a morphological change of the cellulose samples associated with the transition of crystalline structure to amorphous. By using 2D band shift correlation analysis, it becomes possible to sort out detailed information on the sequential order of physical and chemical transitions represented by band position shifts.