Infrared Spectroscopy Applied Research, Licorice Quality Analysis

Current quality analytical methods on Glycyrrhiza has some significant problems, including complicated and time-consuming procedure, big expenditure and environment pollution. In order to solve these problems, this paper sets the powder of raw materials of Glycyrrhiza from different sources as the research object, utilizes IR spectroscopy technology, and combines it with Chemometrics software and other chemical measurements. At last, the fast quality analytical method for Glycyrrhiza is built respectively from qualitative and quantitative aspects.The main research results are as followed:(1)Through comparing the 1D IR spectra and its second derivative IR spectra of the powder of raw materials and the extract of Glycyrrhiza with the corresponding spectra of several reference substances, the IR characteristic peak of certain constituents in Glycyrrhiza are found.IR characteristic absorption peaks in Glycyrrhiza are 1020cm-1(stretching vibration of glucoside C-O in starch),1047 cm-1(stretching vibration of glucoside C-O in sucrose),1318cm-1 (stretching vibration of C-O),1512cm-1 (skeleton vibration of benzene ring),1703 cm-1(stretching vibration of acid anhydride C=O)。Characteristic absorption peaks in second direvative spectra are 1745cm-1 (stretching vibration of C=O in carboxylic acid) and 1386cm-1 (deformation vibration of C-H)(2) Through the Chemometrics method such as PLS to combine the IR spectroscopy with the result of HPLC. The models used for quantitative prediction of Liquiritin and Glycyrrhizic acid in raw powder of Glycyrrhiza are built. The RSD value in prediction group is in the region of-4.72%-5.03%, which indicates the prediction result is fine. The detection ranges are Glycyrrhizic acid 2.285-6.093mg/100mg, Liquiritin 1.117-4.954mg/100mg. The precision and capability of prediction have relation with the number and content of the samples in calibration group. The examination of the effectiveness of the models built by NIR and MIR spectroscopy shows that the two kinds of spectroscopy can successfully build quantitative model for the raw powder of Glycyrrhiza with the help of Chemometrics method.(3)Through the PLS method to combine the resμlts of IR spectroscopy with the data of content determination of Polysaccharide such as sucrose and starch by H2SO4-Anthrone Coloration, the models for predicting Polysaccharide in Glycyrrhiza are built. The RSD value in prediction group of sucrose is in the region of-1.68%-1.94%, the RSD value in prediction group of starch is in-8.35%-8.71%. The detection ranges are sucrose 1.010-2.081μg/mg, starch 1.014-2.382μg/mg.(4) The height of characteristic peaks in IR spectroscopy has positive relationship with the content of corresponding constituents. The content in wild Glycyrrhiza is higher than the content in cultivated samples. The important effects of growth age and cultivated condition are on the quality of the medicinal herb. The samples from different species have many similarities, so that it is only indicated that the contents of flavonoid constituents and starch have some differences.