Research On Rapid Identification And Degradation Of Polysaccharide Using Ambient Plasma-based Mass Spectrometry Technology

Plant polysaccharides have significant effects on the treatment of diabetes.In recent years,ambient mass spectrometry（AMS）technology has been recognized as a quick and convenient analysis tool for obtaining fingerprints,which is attributed to its characteristics of no sample pretreatment and easy operation under atmospheric pressure.However,it is difficult to obtain fingerprints of polysaccharides by AMS due to their resistance for desorption and ionization.Therefore,it is still a challenge to accurately identify the fingerprints of macromolecular polysaccharides using ambient micro-fabrication glow discharge plasma（MFGDP）.In this study,a novel method was introduced for the rapid identification of polysaccharides.Specifically,based on the combination of methylation and temperature programmed system（TPS）,rapid analysis of polysaccharide mixtures is achieved through ambient micro-fabrication glow discharge plasma desorption ionization mass spectrometry（MFGDP-MS）.At the same time,in order to successfully extend the technology of ambient plasma to the application research of polysaccharide degradation,based on the research background that low molecular weight chitosan（LMWC）has more biological activity,the preparation technology of LMWC by microwave induced plasma desorption/ionization（MIPDI）was explored.The main work and research results are as follows:1)In order to meet the requirements of AMS pretreatment,the simplified methylation method in this study has the advantages of time saving and simplicity.The self-made TPS not only makes up for the low desorption efficiency of MFGDP,but also has the advantages of low cost,low ion transmission loss,operation under normal pressure,and wide application range compared with the laser-assisted desorption device reported in the literature.At the optimal temperature of TPS,oligosaccharides,plant polysaccharides and polysaccharide mixtures can be successfully characterized by TPS-MFGDP-MS.In the proposed method,the characteristic[M+NH₄]⁺adduct ions of oligosaccharides ions of oligosaccharides that are difficult for ambient mass spectrometric methods were abundantly produced,making it possible to simultaneously identify five or more polysaccharide mixtures.In addition,the algorithm-based random forest（RF）supervised classification model was used to classify 7typical hypoglycemic polysaccharides with good sensitivity,specificity and accuracy,indicating that the constructed RF model has good classification performance.2)Considering that the degradation parameters of MIPDI are of great significance to the degradation efficiency of CTS.First,by optimizing the degradation parameters of MIPDI,the degradation rate of chitosan can reach 61%within 60 min.Then,the types of active ions and their content at different reaction interfaces were studied by spectroscopy.The results showed that MIPDI has the most abundant?OH content at the gas-liquid interface.At the same time,the active particles represented by?OH can degrade chitosan with a molecular weight of 540KDa into water-soluble chitosan（≤10 KDa）.Finally,the structural changes before and after degradation of CTS were explored by FT-IR,XRD,FE-SEM,TGA,UV-vis,UPLC-MS and other characterization methods.The results show that the chain structure and crystal structure would gradually degrade as the treatment time increased while the chemical structure of chitosan did not change significantly.