Study On The Detection Technologies Of Plant Medicines And Foods Based On Terahertz Spectroscopy And Chemometrics

With the development of social economy and the improvement of people's living standards,health problems have become a hot issue that people pay attention to.Traditional food and medicine testing methods often have problems such as long testing time,complicated processes,and possible destruction of sample components,therefore,fast and safe testing methods are particularly important.Terahertz wave is electromagnetic radiation with frequency range of 0.1 ~ 10 THz,which is in the crossover region of electronics to photonics.This frequency band can be used to observe intermolecular forces,analyze crystal lattice vibration,molecular collective vibration and other microscopic processes.In recent years,it has been widely used in qualitative and quantitative research in the fields of chemistry,medicine,and biological materials.In this paper,terahertz time-domain spectroscopy is used to measure the spectrum of several commonly used compounds in the field of food and medicine,and combined with quantum chemical calculations to simulate the system of single molecules,polymers(dimers),unit cells,etc.And complete the identification of the vibration mode of the corresponding characteristic peak;study the identification of terahertz spectra of chiral compounds;study the terahertz spectrum of several plant extracts;measure several kinds of traditional Chinese medicine,and combine chemometrics methods to complete the spectral data cluster visualization and classification analysis.Mainly done the following research:(1)Terahertz spectra of several small molecular compounds were measured.Taking benzoic acid,sodium benzoate and sorbic acid as examples,B3 LYP functional and B3PW91 functional were used to simulate their monomolecular and dimer structures,and the optimized bond length and bond angle parameters were compared with the experimental values in the literature.Identify the vibration mode of the theoretical characteristic peaks which are more consistent with the experimental.The limitation of single molecular structure is explained,which provides reference for structure construction,optimization and method selection in simulation process.(2)Study the identification of terahertz spectra of chiral compounds.The terahertz spectra of 6 drugs including three different configurations of asparagine and monohydrate compounds were measured,through two sets of heating experiments;And complete the L-asparagine,L-asparagine monohydrate compound cell simulation,The effect of crystal water on the crystal structure is expounded from the aspect of material structure,and it also shows the advantages of terahertz spectroscopy in identifying chiral compounds.(3)The terahertz spectra of several coumarin compounds were measured,and the characteristic peaks were summarized.The results show that terahertz spectroscopy technology also has broad prospects in the quality detection of plant extracts.(4)Using terahertz spectral data,selecting the detection results of a certain frequency band as a feature,complete the clustering visual analysis and classification identification of several confusing Chinese medicines with similar appearance and similar composition but different prices and efficacy.Provide experimental data support and research method reference for qualitative analysis of traditional Chinese medicine.This study starts with compounds with simple compositions,explores the fingerprints of different compounds in the terahertz band,and combines molecular simulations to deeply understand the impact of molecular structure systems on the physical and chemical properties of the material and its terahertz absorption.In the study of terahertz spectroscopy of traditional Chinese medicine with relatively complex ingredients,a large number of experiments are combined with stoichiometry to study the optical properties of botanical medicines.The results prove that terahertz spectroscopy has unique advantages in substance detection and identification.