Evaluation on intrinsic quality of licorice influenced by environmental factors by using FTIR combined with 2D-IR correlation spectroscopy

To evaluate the intrinsic quality of licorice influenced by environmental factors, the spectral comparison of licorice from two typical ecological habitats was conducted by using FTIR and 2D-IR correlation spectroscopy. There were differences in the peak intensities of 1155, 1076 and 1048 cm−1 of FTIR profiles. The difference was amplified by the second derivative spectrum for the peak intensities at 1370, 1365 and 1317 cm−1 and the peak shape in 958–920 cm−1 and 1050–988 cm−1. The synchronous 2D-IR spectra within the range of 860–1300 cm−1 were classified into type I and type II and their frequency in the two groups was noticeably different. Although the chemical compounds of licorice samples from two areas were generally similar, the contents of starch, calcium oxalate, and some chemical compounds containing alcohol hydroxyl group were different, indicating the influence of precipitation and temperature. This study demonstrates that the systematical analysis of FTIR, the second derivative spectrum and 2D-IR can effectively determine the differences in licorice samples from different ecological habitats.