Application of Open Ionization Mass Spectrometry in the Study of Chinese Herbal Medicine
Chinese query network open microbial strains ionization mass spectrometry (ambient ionization mass spectrometry, AIMS) without a rise in recent years (or slightly) before the sample processing steps, to achieve ionization of the atmosphere at the open mass spectrometry. In recent years, the development and application of various AIMS technologies has become one of the focuses of attention in the field of mass spectrometry. This work summarizes the application of AIMS technology in Chinese herbal medicine research, discusses typical analysis strategies, expounds the basic principles, characteristics and classification of AIMS technology, and forecasts the future development trend and possibility of this technology in the field of traditional Chinese medicine research. Impact.
Ambient ionization mass spectrometry (AIMS) is a new mass spectrometry technology that directly analyzes sample or sample surface materials in an open, atmospheric environment without the need for (or simply) pre-samples. The processing can realize the analysis of the sample, and has a series of advantages such as real-time, in-situ, high-throughput, simple and rapid, environmental protection, and can be combined with various mass spectrometer instruments, and has high analysis speed and high sensitivity of traditional mass spectrometry. Features. In 2004, the Cooks group first proposed desorption electrospray ionization (DESI) technology on the basis of electrospray ionization. In 2005, Cody et al. developed a direct analysis in real time (DART) technique based on atmospheric pressure chemical ionization. At the same time, Xie Jiantai et al. developed a similar electrospray-assisted laser desorption ionization mass spectrometry technique. In turn, the development of AIMS has attracted wide attention, and various new technologies have emerged. At present, there are more than 40 kinds of AIMS technologies. In order to promote the innovation and development of AIMS technology, the AIMS International Academic Conference, co-sponsored by China Mass Spectrometry Society and Huamao Tyco Biotechnology (Beijing) Co., Ltd., has been successfully held four times since 2013, leading AIMS technology to various The industry penetrates layer by layer, deeply affecting the development and utilization of the next generation of analytical detection technology. Compared with classical electrospray, atmospheric pressure chemical ionization and atmospheric pressure photoionization, AIMS has less solvent consumption, stronger salt and matrix resistance, and AIMS's open structure and modular design make it convenient. It is connected to various mass spectrometers, which greatly reduces the cost of instrument acquisition. This technology has shown wide application prospects in many fields such as medicine, pharmacy, food safety, environmental pollutant monitoring, explosives detection, biomolecular and metabolite characterization, and molecular imaging. Therefore, the basic and applied research of AIMS has attracted the attention of mass spectrometers. The basic research mainly focuses on constructing and developing a new type of AIMS ion source, and exploring the corresponding ionization mechanism. The applied research is mainly to qualitatively and quantitatively analyze various practical samples. . This work focuses on the application of AIMS in Chinese herbal medicine research. Through the discussion of typical analysis strategies, the basic principles, characteristics and classification of AIMS technology are expounded, and the possible trends and influences of this technology in the future development of traditional Chinese medicine research are prospected.
1. Basic principles, characteristics and classification of open ionization mass spectrometry
AIMS integrates three core steps: sample in-situ desorption, real-time ionization of the analyte, and ion transport to the mass analyzer. Let's take DART as an example to introduce the basic principle of ionization: use He or N2 as the working gas to pass through the discharge chamber, and apply a voltage of up to several thousand volts between the cathode and the anode inside the discharge chamber to cause high-voltage glow discharge to work. Gas ionization becomes a plasma gas stream containing excited gas atoms or molecules, ions, and electrons. The plasma gas stream flows through the disk electrode, selectively removes certain ions and is heated, and the heated plasma gas stream is ejected from the DART port to the surface of the sample to complete the thermally assisted desorption and ionization process. The ionization mechanism is generally considered to include processes such as Penning ionization of the surrounding gas by the excited working gas, further proton transfer, and other types of gas phase ion molecular reactions. The AIMS technology not only can ionize the sample under normal pressure, but also the open structure of the ion source is easy to achieve direct ionization and mass spectrometry on the surface of the object. This type of ion source is simple and fast to operate and requires no complicated sample preparation. Another important feature of AIMS technology is fast and high throughput. Usually, the analysis time of each sample is less than 5s, which fully demonstrates the advantages of rapid mass spectrometry and provides a new and effective way for high-throughput analysis. Therefore, the atmospheric open ion source opens up a wide range of applications in the fields of direct and rapid analysis, surface and in-situ analysis of mass spectrometry without sample preparation.
AIMS ion sources can be divided into three categories according to their ionization process and mechanism: 1) Direct ionization ion source. The sample is directly ionized into a high electric field, such as a number of ion sources developed on the basis of the ESI source, including direct electrospray probe ionization (DEPI), probe electrospray ionization (PESI), Paper spray ionization (PSI), Field induced droplet ionization (FIDI), and Ultra-sound ionization (USI); 2) Direct desorption of ionized ion source while simultaneously acting on the sample The role of desorption and ionization. Including Desorption electrospray ionization (DESI), Electrode-assisted desorption electrospray ionization (EADESI), Easy ambient sonic spray ionization (EASI), Desorption atmospheric pressure chemical ionization Desorption atmospheric pressure chemical ionization (DAPCI), Dielectric barrier discharge ionization (DBDI), Plasma-assisted desorption ionization (PADI), Atmospherical glow discharge ionization (APGDI) ), Desorption corona beam ionization (DCBI), Laser spray ionization (LSI), etc.; 3) Ionized ion source after desorption. This is a two-step mechanism ion source. The first step is to desorb the analyte, and the second step is to achieve the ionization process of the analyte, including gas chromatography electrospray ionization (GC-ESI). , Secondary electrospray ionization (SESI), Fused droplet electrospray ionization (FD-ESI), Extractive electrospray ionization (EESI), Liquid surface Penning ionization mass spectrometry ( Liquid surface Penning ionization (LPI), Atmospheric pressure Penning ionization (APPeI), Electrospray laser desorption ionization (ELDI), Matrix-assisted laser desorption electrospray ionization (Matrix-assisted laser desorption electrospray ionization, MALDESI), Laser ablation electrospray ionization (LAESI), Infrared laser-assisted desorption electrospray ionization (IR-LADESI), Laser electrospray ionization (LESI), Laser desorption spray Laser desorption spray post-ionization (LDSPI), laser-induced acoustic desorption electrospray ionization (LIAD-ESI), laser desorption-atmospheric pressure chemical ionization (Laser desorption-atmospheric pressure chemical ionization) LD-APCI), laser diode thermal desorption (LDTD), electrospray-assisted pyrolysis ionization (ESA-Py), atmospheric pressure thermal desorption-electrospray ionization (Atmospheric pressure) Thermal desorption-electrospray ionization (AP-TD/ESI), based on thermal desorption-based ambient ionization (TDAI), atmospheric pressure solids analysis probe (ASAP), real-time direct analysis (Direct Analysis in real time, DART), desorption atmospheric pressure photoionization (DAPPI), and the like.
2. Application of open ionization mass spectrometry in Chinese herbal medicine research <br> Establish a new method to analyze the medicinal ingredients and impurities in Chinese herbal medicine, which is of great significance for the quality evaluation and quality control of Chinese herbal medicine. The development of open ionization mass spectrometry provides a fast and direct means for the analysis of Chinese herbal medicine. This paper reviews the application of different types of open-ended ionization mass spectrometry in the analysis of Chinese herbal medicines, and discusses typical analysis cases.
(1) Direct ionization ion source The direct ionization ion source is a direct ionization open ionization mass spectrometry technology based on the electrospray principle, and the analyte in the sample tissue is directly ionized for mass spectrometry. This technology is fast, direct, real-time, in-situ, without sample preparation, and is suitable for direct analysis of Chinese herbal medicines. The main application techniques include: Direct ionization, Tissue spray, Leaf spray, Direct plant spray Field-induced DI, Internal extraction electrospray Internal extractive electrospray ionization mass spectrometry (iEESI) and the like. Although the names of these technologies are different, their principles and analytical strategies are similar, that is, using the sample itself as a solid substrate, using a solvent and a high voltage to dissolve or extract the analyte into a solvent, and the liquid phase analyte molecules are at a high electric field. Direct ionization, spraying, generation of charged droplets and ions for mass spectrometry.
Yao Zhongping's research group has done a lot of research work on the mechanism and application of electrospray ionization under solid matrix. Solid matrix electrospray ionization is the attachment of powders, suspensions and extracts of Chinese herbal medicines to solid substrates for direct ionization analysis. Available solid substrates include: pure metal probes, paper triangles, wood chips, aluminum foil, pipette tips, etc. . Because of its inertness, impermeability and relative rigidity, the aluminum foil can be folded to carry the solvent, and the powder sample is purposefully extracted, and electrospray ionization mass spectrometry is performed in an open environment. Aluminum foil electrospray ionization mass spectrometry has been successfully applied to the determination of main components in traditional Chinese medicine powder samples such as American ginseng and aconite. The pipette head mode is analyzed by connecting the pipette head to the mass spectrometer and the injection pump, extracting the traditional Chinese medicine powder in the injector head, and applying high voltage to the charged organic solvent to extract the analyte through the traditional Chinese medicine powder. Post ionization, analysis by mass spectrometry. The analysis of this pipette head mode has been successfully applied to the determination of saponins in ginseng, American ginseng and Panax notoginseng, lignans in Schisandra chinensis and alkaloids in various medicinal materials.
(2) Direct desorption of ionized ions Since the advent of DESI, its application in Chinese herbal medicine analysis has been reported. The main methods used include: surface desorption ionization of the analyte, direct desorption ionization of the reaction, surface imaging of the analyte, thin layer chromatography and direct desorption ionization mass spectrometry, etc., the most widely used is the surface desorption ionization of the analyte, without The pretreatment of Chinese herbal medicine samples can be directly analyzed.
DAPCI is an atmospheric piezoelectric corona discharge that generates electrons, protons, metastable atoms, hydronium ions and protonated solvent ions from chemical reagents to desorb the analytes on the surface of the ionized sample for mass spectrometry analysis, mainly for the analysis of low molecular masses. Volatile or semi-volatile compounds. The reported studies have analyzed the terpenoids in the Schisandra chinensis and the saponins in the ginseng and red ginseng.
DCBI applies a high DC voltage to the sharp needle to induce a helium atom corona discharge, generates excited state ions near the corona needle, reacts with the analyte on the surface of the sample, and produces a single charge analyte ion for mass spectrometry analysis. The use of DCBI to analyze low-polarity components in Chinese herbal medicines is extremely challenging. In order to solve this difficulty, a design scheme was reported in the literature. The reagents (saturated sodium hydroxide and methanol solution, 3:7, V/V) were added to the sample to improve the ionization efficiency of DCBI, and the method was successfully applied. The alkaloids were determined in 6 kinds of Chinese herbal medicines, and they were combined with TLC to determine the alkaloid content.
(3) Ionized ion source after desorption
DART-MS is an open-source ionization mass spectrometry technology widely used in the analysis of Chinese herbal medicines. Its ion source is currently commercially available. The main analytical strategies of DART-MS include: surface desorption ionization of the analyte, placing the sample in the DART source and mass spectrometry inlet; analysis of the powder sample, ionizing the glass capillary (rod) of the filled sample in a gas beam heated by the DART source Liquid sample analysis, the sample is dropped on the melting point tube (dip tube), metal screen (stainless steel metal grid), placed between the DART source and the mass spectrometer inlet; TLC and DART-MS combined analysis, is the compound in After separation on the thin plate, the thin plate is placed between the DART source and the mass spectrometer inlet, and the analyte is subjected to pyrolysis adsorption of the heated gas, and the analyte is ionized and then introduced into the mass spectrometer for analysis by ion-molecule reaction.
EESI and nano-EESI are open ionization mass spectrometry based on electrospray ionization. The invention was originally applied to the analysis of liquid and gaseous samples. The analyte was extracted from the solution phase or gas phase sample to generate ions via electrospray ionization. Mass spectrometry was performed. Chen Huanwen's research team successfully applied Nano-EESI-MS technology to the determination of ginsenosides in ginseng. The open ionization technique (LAESI), which combines laser desorption or ablation with electrospray, is suitable for solid sample analysis. The main applications in Chinese herbal medicine analysis are: composition analysis of peacock roots, stems and leaves, and sage in sage leaves. Determination of class components. The combination of open ionization technology and photoionization principle is applied in the research of Chinese herbal medicine. There are two main methods: desorption atmospheric pressure chemical ionization (DAPPI) and laser ablation atmospheric pressure photoionization (LAAPPI). These two methods enable efficient ionization of non-polar and neutral analytes on the surface of the sample for mass spectrometry. In addition, these two methods also have surface imaging functions, such as DAPPI-MS and LAAPPI-MS techniques in the composition of sage leaves. The application of surface imaging research, as well as DAPPI-MS analysis of the main medicinal components in the clam shell leaves. Plasma-assisted laser desorption mass spectrometry (PALDI-MS) has been successfully used to study the imaging of baicalein and wogonin in Astragalus membranaceus. The results show that this component is concentrated in the edge of the epidermal vascular bundle of the root.
(4) Application in quality evaluation and quality control of Chinese herbal medicine With the continuous development of open ionization mass spectrometry technology, it is widely used in the rapid evaluation and control of Chinese herbal medicine quality. The open ionization mass spectrometry fingerprint analysis method can give the overall chemical profile of the Chinese herbal medicine component, and can be used to evaluate the stability of the Chinese herbal medicine quality, trace the source, and identify the authenticity. To evaluate and control the quality of Chinese herbal medicine by open-ended ionization mass spectrometry, we first choose a suitable open ionization technology, establish a fingerprint analysis method, analyze the sample, and use the multivariate statistical analysis method. For example, principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), cluster analysis (HCA), and the like.
At present, using DART-MS technology combined with a variety of statistical analysis methods, successfully distinguishing different cultivars of loquat leaves; distinguishing different varieties of traditional Chinese medicines of Datura, Rauvolfia, Cucurbita and Umbelliferae, and identified The iconic chemical composition; distinguishes the angelica from different sources; identifies the iconic chemical components of Chuanwu, and distinguishes the degree of processing. DAPCI-MS technology combined with PCA analysis was applied to the study of Schisandra chinensis in South and North, and different cultivars and wild varieties were successfully distinguished, and different types of processed products were distinguished. Using Wooden-tipESI-MS combined with PCA and PLS-DA technology, the varieties of Fritillaria chinensis powder were identified and the counterfeit products were distinguished.
(5) The identification and quantitative analysis of Chinese herbal medicines in the research work of this laboratory is one of the important development directions of AIMS in recent years. The laboratory uses commercial DART as the ion source, and the developed method has strong repeatability and practical application. value. The research content mainly includes five aspects.
1 Rapid analysis of traditional Chinese medicine: The chemical constituents of 8 traditional Chinese medicines were studied, and the rapid and direct analysis of alkaloids, flavonoids and some ginsenosides was realized. The ionization mechanism of DART was discussed in depth.
2DART quantitative analysis of traditional Chinese medicine ingredients: DART quantitative analysis of the functional components of Chinese herbal medicine, Corydalis, and DART, and DART quantitative analysis of ginsenosides by methylation and deuterated internal standard;
3 Analysis of the difficult ionization components of DART technology: For the first time, the laboratory used the transient derivatization reagent tetramethylammonium hydroxide to carry out transient methylation in the DART source of saponin and oligosaccharide components, and increased the saponin content by methylation. Volatile, the formation of ammonium adduct ions, the realization of DART analysis of polyhydroxy compounds (such as ginsenosides and oligosaccharides). Among them, tetramethylammonium hydroxide not only plays a role in derivatization, but also enhances the sensitivity of saponin components in DART as an auxiliary ionization reagent [62]. Because the reaction is a free radical reaction, the reaction control is difficult, and the repeatability needs to be improved;
4DART is used for the detection of pesticide residues: DART rapid detection research has been carried out on more than 100 kinds of pesticide residues. It is found that many pesticide components not only have additive ions (ion-molecular reaction products) but also fragments in the DART ionization process (excessive Energy production), in addition, experiments have found that organophosphorus pesticides will undergo oxidation reaction of oxygen-sulfur exchange, and its reaction mechanism is discussed in depth;
5 Research on DART ionization mechanism: It is found that different working gases (helium, argon, nitrogen, etc.) have different characteristics due to their different ionization energies and the vibrational freedom of nitrogen, which makes them exhibit different characteristics in the ionization process. Although helium has a wider range of applications due to higher ionization energy, in some cases, less argon and nitrogen (lower than helium) produced by the ionization energy produce fewer fragments of the test compound, and then introduce it appropriately. The make up reagent can effectively increase the sensitivity of the analyte. It has been found that fluorobenzene and acetone with lower ionization energy can be used as auxiliary reagents to significantly improve the analytical sensitivity of the analyte.
3. Summary and Outlook <br> The safety and effectiveness of Chinese medicine quality depends mainly on the medicinal ingredients and impurities contained in it. This requires the application of fast and reliable analytical methods to evaluate and control the quality of Chinese herbal medicines. At present, a variety of open ionization mass spectrometry techniques have been successfully applied to the detection of various types of chemical components in a variety of traditional Chinese medicines, and comprehensive evaluation and quality control of the quality of various traditional Chinese medicines. In general, for components with higher volatility or higher proton affinity, such as alkaloids, flavonoids, etc., ionization can occur directly near the surface of plant tissue without the need for solvents and other matrices. In order to obtain good analytical results, solvent-assisted components such as saponins are required, and analysis of saccharide components requires even simple derivatization. One of the principles of open ionization sources is the gas phase ion-molecule reaction around the analyte. These reactions are difficult to achieve the classical closed CI source equilibrium conditions. Therefore, there are some difficulties in experimental conditions and data repeatability. It is still necessary to continuously improve the technology itself. In addition, accurate methods for the quantification of analytes are yet to be developed and improved. These problems require the continuous attention and research of analytical chemists and mass spectrometers. It is believed that in the near future, the analytical methods combining open ionization technology and small mass spectrometry instruments can be applied to the field production and finished drug production lines of traditional Chinese medicine production. More traditional Chinese medicine fields, such as the aid of Chinese medicine diagnosis, play a greater role in promoting the modern development of traditional Chinese medicine.
Chinese query network open microbial strains ionization mass spectrometry (ambient ionization mass spectrometry, AIMS) without a rise in recent years (or slightly) before the sample processing steps, to achieve ionization of the atmosphere at the open mass spectrometry. In recent years, the development and application of various AIMS technologies has become one of the focuses of attention in the field of mass spectrometry. This work summarizes the application of AIMS technology in Chinese herbal medicine research, discusses typical analysis strategies, expounds the basic principles, characteristics and classification of AIMS technology, and forecasts the future development trend and possibility of this technology in the field of traditional Chinese medicine research. Impact.
Ambient ionization mass spectrometry (AIMS) is a new mass spectrometry technology that directly analyzes sample or sample surface materials in an open, atmospheric environment without the need for (or simply) pre-samples. The processing can realize the analysis of the sample, and has a series of advantages such as real-time, in-situ, high-throughput, simple and rapid, environmental protection, and can be combined with various mass spectrometer instruments, and has high analysis speed and high sensitivity of traditional mass spectrometry. Features. In 2004, the Cooks group first proposed desorption electrospray ionization (DESI) technology on the basis of electrospray ionization. In 2005, Cody et al. developed a direct analysis in real time (DART) technique based on atmospheric pressure chemical ionization. At the same time, Xie Jiantai et al. developed a similar electrospray-assisted laser desorption ionization mass spectrometry technique. In turn, the development of AIMS has attracted wide attention, and various new technologies have emerged. At present, there are more than 40 kinds of AIMS technologies. In order to promote the innovation and development of AIMS technology, the AIMS International Academic Conference, co-sponsored by China Mass Spectrometry Society and Huamao Tyco Biotechnology (Beijing) Co., Ltd., has been successfully held four times since 2013, leading AIMS technology to various The industry penetrates layer by layer, deeply affecting the development and utilization of the next generation of analytical detection technology. Compared with classical electrospray, atmospheric pressure chemical ionization and atmospheric pressure photoionization, AIMS has less solvent consumption, stronger salt and matrix resistance, and AIMS's open structure and modular design make it convenient. It is connected to various mass spectrometers, which greatly reduces the cost of instrument acquisition. This technology has shown wide application prospects in many fields such as medicine, pharmacy, food safety, environmental pollutant monitoring, explosives detection, biomolecular and metabolite characterization, and molecular imaging. Therefore, the basic and applied research of AIMS has attracted the attention of mass spectrometers. The basic research mainly focuses on constructing and developing a new type of AIMS ion source, and exploring the corresponding ionization mechanism. The applied research is mainly to qualitatively and quantitatively analyze various practical samples. . This work focuses on the application of AIMS in Chinese herbal medicine research. Through the discussion of typical analysis strategies, the basic principles, characteristics and classification of AIMS technology are expounded, and the possible trends and influences of this technology in the future development of traditional Chinese medicine research are prospected.
1. Basic principles, characteristics and classification of open ionization mass spectrometry
AIMS integrates three core steps: sample in-situ desorption, real-time ionization of the analyte, and ion transport to the mass analyzer. Let's take DART as an example to introduce the basic principle of ionization: use He or N2 as the working gas to pass through the discharge chamber, and apply a voltage of up to several thousand volts between the cathode and the anode inside the discharge chamber to cause high-voltage glow discharge to work. Gas ionization becomes a plasma gas stream containing excited gas atoms or molecules, ions, and electrons. The plasma gas stream flows through the disk electrode, selectively removes certain ions and is heated, and the heated plasma gas stream is ejected from the DART port to the surface of the sample to complete the thermally assisted desorption and ionization process. The ionization mechanism is generally considered to include processes such as Penning ionization of the surrounding gas by the excited working gas, further proton transfer, and other types of gas phase ion molecular reactions. The AIMS technology not only can ionize the sample under normal pressure, but also the open structure of the ion source is easy to achieve direct ionization and mass spectrometry on the surface of the object. This type of ion source is simple and fast to operate and requires no complicated sample preparation. Another important feature of AIMS technology is fast and high throughput. Usually, the analysis time of each sample is less than 5s, which fully demonstrates the advantages of rapid mass spectrometry and provides a new and effective way for high-throughput analysis. Therefore, the atmospheric open ion source opens up a wide range of applications in the fields of direct and rapid analysis, surface and in-situ analysis of mass spectrometry without sample preparation.
AIMS ion sources can be divided into three categories according to their ionization process and mechanism: 1) Direct ionization ion source. The sample is directly ionized into a high electric field, such as a number of ion sources developed on the basis of the ESI source, including direct electrospray probe ionization (DEPI), probe electrospray ionization (PESI), Paper spray ionization (PSI), Field induced droplet ionization (FIDI), and Ultra-sound ionization (USI); 2) Direct desorption of ionized ion source while simultaneously acting on the sample The role of desorption and ionization. Including Desorption electrospray ionization (DESI), Electrode-assisted desorption electrospray ionization (EADESI), Easy ambient sonic spray ionization (EASI), Desorption atmospheric pressure chemical ionization Desorption atmospheric pressure chemical ionization (DAPCI), Dielectric barrier discharge ionization (DBDI), Plasma-assisted desorption ionization (PADI), Atmospherical glow discharge ionization (APGDI) ), Desorption corona beam ionization (DCBI), Laser spray ionization (LSI), etc.; 3) Ionized ion source after desorption. This is a two-step mechanism ion source. The first step is to desorb the analyte, and the second step is to achieve the ionization process of the analyte, including gas chromatography electrospray ionization (GC-ESI). , Secondary electrospray ionization (SESI), Fused droplet electrospray ionization (FD-ESI), Extractive electrospray ionization (EESI), Liquid surface Penning ionization mass spectrometry ( Liquid surface Penning ionization (LPI), Atmospheric pressure Penning ionization (APPeI), Electrospray laser desorption ionization (ELDI), Matrix-assisted laser desorption electrospray ionization (Matrix-assisted laser desorption electrospray ionization, MALDESI), Laser ablation electrospray ionization (LAESI), Infrared laser-assisted desorption electrospray ionization (IR-LADESI), Laser electrospray ionization (LESI), Laser desorption spray Laser desorption spray post-ionization (LDSPI), laser-induced acoustic desorption electrospray ionization (LIAD-ESI), laser desorption-atmospheric pressure chemical ionization (Laser desorption-atmospheric pressure chemical ionization) LD-APCI), laser diode thermal desorption (LDTD), electrospray-assisted pyrolysis ionization (ESA-Py), atmospheric pressure thermal desorption-electrospray ionization (Atmospheric pressure) Thermal desorption-electrospray ionization (AP-TD/ESI), based on thermal desorption-based ambient ionization (TDAI), atmospheric pressure solids analysis probe (ASAP), real-time direct analysis (Direct Analysis in real time, DART), desorption atmospheric pressure photoionization (DAPPI), and the like.
2. Application of open ionization mass spectrometry in Chinese herbal medicine research <br> Establish a new method to analyze the medicinal ingredients and impurities in Chinese herbal medicine, which is of great significance for the quality evaluation and quality control of Chinese herbal medicine. The development of open ionization mass spectrometry provides a fast and direct means for the analysis of Chinese herbal medicine. This paper reviews the application of different types of open-ended ionization mass spectrometry in the analysis of Chinese herbal medicines, and discusses typical analysis cases.
(1) Direct ionization ion source The direct ionization ion source is a direct ionization open ionization mass spectrometry technology based on the electrospray principle, and the analyte in the sample tissue is directly ionized for mass spectrometry. This technology is fast, direct, real-time, in-situ, without sample preparation, and is suitable for direct analysis of Chinese herbal medicines. The main application techniques include: Direct ionization, Tissue spray, Leaf spray, Direct plant spray Field-induced DI, Internal extraction electrospray Internal extractive electrospray ionization mass spectrometry (iEESI) and the like. Although the names of these technologies are different, their principles and analytical strategies are similar, that is, using the sample itself as a solid substrate, using a solvent and a high voltage to dissolve or extract the analyte into a solvent, and the liquid phase analyte molecules are at a high electric field. Direct ionization, spraying, generation of charged droplets and ions for mass spectrometry.
Yao Zhongping's research group has done a lot of research work on the mechanism and application of electrospray ionization under solid matrix. Solid matrix electrospray ionization is the attachment of powders, suspensions and extracts of Chinese herbal medicines to solid substrates for direct ionization analysis. Available solid substrates include: pure metal probes, paper triangles, wood chips, aluminum foil, pipette tips, etc. . Because of its inertness, impermeability and relative rigidity, the aluminum foil can be folded to carry the solvent, and the powder sample is purposefully extracted, and electrospray ionization mass spectrometry is performed in an open environment. Aluminum foil electrospray ionization mass spectrometry has been successfully applied to the determination of main components in traditional Chinese medicine powder samples such as American ginseng and aconite. The pipette head mode is analyzed by connecting the pipette head to the mass spectrometer and the injection pump, extracting the traditional Chinese medicine powder in the injector head, and applying high voltage to the charged organic solvent to extract the analyte through the traditional Chinese medicine powder. Post ionization, analysis by mass spectrometry. The analysis of this pipette head mode has been successfully applied to the determination of saponins in ginseng, American ginseng and Panax notoginseng, lignans in Schisandra chinensis and alkaloids in various medicinal materials.
(2) Direct desorption of ionized ions Since the advent of DESI, its application in Chinese herbal medicine analysis has been reported. The main methods used include: surface desorption ionization of the analyte, direct desorption ionization of the reaction, surface imaging of the analyte, thin layer chromatography and direct desorption ionization mass spectrometry, etc., the most widely used is the surface desorption ionization of the analyte, without The pretreatment of Chinese herbal medicine samples can be directly analyzed.
DAPCI is an atmospheric piezoelectric corona discharge that generates electrons, protons, metastable atoms, hydronium ions and protonated solvent ions from chemical reagents to desorb the analytes on the surface of the ionized sample for mass spectrometry analysis, mainly for the analysis of low molecular masses. Volatile or semi-volatile compounds. The reported studies have analyzed the terpenoids in the Schisandra chinensis and the saponins in the ginseng and red ginseng.
DCBI applies a high DC voltage to the sharp needle to induce a helium atom corona discharge, generates excited state ions near the corona needle, reacts with the analyte on the surface of the sample, and produces a single charge analyte ion for mass spectrometry analysis. The use of DCBI to analyze low-polarity components in Chinese herbal medicines is extremely challenging. In order to solve this difficulty, a design scheme was reported in the literature. The reagents (saturated sodium hydroxide and methanol solution, 3:7, V/V) were added to the sample to improve the ionization efficiency of DCBI, and the method was successfully applied. The alkaloids were determined in 6 kinds of Chinese herbal medicines, and they were combined with TLC to determine the alkaloid content.
(3) Ionized ion source after desorption
DART-MS is an open-source ionization mass spectrometry technology widely used in the analysis of Chinese herbal medicines. Its ion source is currently commercially available. The main analytical strategies of DART-MS include: surface desorption ionization of the analyte, placing the sample in the DART source and mass spectrometry inlet; analysis of the powder sample, ionizing the glass capillary (rod) of the filled sample in a gas beam heated by the DART source Liquid sample analysis, the sample is dropped on the melting point tube (dip tube), metal screen (stainless steel metal grid), placed between the DART source and the mass spectrometer inlet; TLC and DART-MS combined analysis, is the compound in After separation on the thin plate, the thin plate is placed between the DART source and the mass spectrometer inlet, and the analyte is subjected to pyrolysis adsorption of the heated gas, and the analyte is ionized and then introduced into the mass spectrometer for analysis by ion-molecule reaction.
EESI and nano-EESI are open ionization mass spectrometry based on electrospray ionization. The invention was originally applied to the analysis of liquid and gaseous samples. The analyte was extracted from the solution phase or gas phase sample to generate ions via electrospray ionization. Mass spectrometry was performed. Chen Huanwen's research team successfully applied Nano-EESI-MS technology to the determination of ginsenosides in ginseng. The open ionization technique (LAESI), which combines laser desorption or ablation with electrospray, is suitable for solid sample analysis. The main applications in Chinese herbal medicine analysis are: composition analysis of peacock roots, stems and leaves, and sage in sage leaves. Determination of class components. The combination of open ionization technology and photoionization principle is applied in the research of Chinese herbal medicine. There are two main methods: desorption atmospheric pressure chemical ionization (DAPPI) and laser ablation atmospheric pressure photoionization (LAAPPI). These two methods enable efficient ionization of non-polar and neutral analytes on the surface of the sample for mass spectrometry. In addition, these two methods also have surface imaging functions, such as DAPPI-MS and LAAPPI-MS techniques in the composition of sage leaves. The application of surface imaging research, as well as DAPPI-MS analysis of the main medicinal components in the clam shell leaves. Plasma-assisted laser desorption mass spectrometry (PALDI-MS) has been successfully used to study the imaging of baicalein and wogonin in Astragalus membranaceus. The results show that this component is concentrated in the edge of the epidermal vascular bundle of the root.
(4) Application in quality evaluation and quality control of Chinese herbal medicine With the continuous development of open ionization mass spectrometry technology, it is widely used in the rapid evaluation and control of Chinese herbal medicine quality. The open ionization mass spectrometry fingerprint analysis method can give the overall chemical profile of the Chinese herbal medicine component, and can be used to evaluate the stability of the Chinese herbal medicine quality, trace the source, and identify the authenticity. To evaluate and control the quality of Chinese herbal medicine by open-ended ionization mass spectrometry, we first choose a suitable open ionization technology, establish a fingerprint analysis method, analyze the sample, and use the multivariate statistical analysis method. For example, principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), cluster analysis (HCA), and the like.
At present, using DART-MS technology combined with a variety of statistical analysis methods, successfully distinguishing different cultivars of loquat leaves; distinguishing different varieties of traditional Chinese medicines of Datura, Rauvolfia, Cucurbita and Umbelliferae, and identified The iconic chemical composition; distinguishes the angelica from different sources; identifies the iconic chemical components of Chuanwu, and distinguishes the degree of processing. DAPCI-MS technology combined with PCA analysis was applied to the study of Schisandra chinensis in South and North, and different cultivars and wild varieties were successfully distinguished, and different types of processed products were distinguished. Using Wooden-tipESI-MS combined with PCA and PLS-DA technology, the varieties of Fritillaria chinensis powder were identified and the counterfeit products were distinguished.
(5) The identification and quantitative analysis of Chinese herbal medicines in the research work of this laboratory is one of the important development directions of AIMS in recent years. The laboratory uses commercial DART as the ion source, and the developed method has strong repeatability and practical application. value. The research content mainly includes five aspects.
1 Rapid analysis of traditional Chinese medicine: The chemical constituents of 8 traditional Chinese medicines were studied, and the rapid and direct analysis of alkaloids, flavonoids and some ginsenosides was realized. The ionization mechanism of DART was discussed in depth.
2DART quantitative analysis of traditional Chinese medicine ingredients: DART quantitative analysis of the functional components of Chinese herbal medicine, Corydalis, and DART, and DART quantitative analysis of ginsenosides by methylation and deuterated internal standard;
3 Analysis of the difficult ionization components of DART technology: For the first time, the laboratory used the transient derivatization reagent tetramethylammonium hydroxide to carry out transient methylation in the DART source of saponin and oligosaccharide components, and increased the saponin content by methylation. Volatile, the formation of ammonium adduct ions, the realization of DART analysis of polyhydroxy compounds (such as ginsenosides and oligosaccharides). Among them, tetramethylammonium hydroxide not only plays a role in derivatization, but also enhances the sensitivity of saponin components in DART as an auxiliary ionization reagent [62]. Because the reaction is a free radical reaction, the reaction control is difficult, and the repeatability needs to be improved;
4DART is used for the detection of pesticide residues: DART rapid detection research has been carried out on more than 100 kinds of pesticide residues. It is found that many pesticide components not only have additive ions (ion-molecular reaction products) but also fragments in the DART ionization process (excessive Energy production), in addition, experiments have found that organophosphorus pesticides will undergo oxidation reaction of oxygen-sulfur exchange, and its reaction mechanism is discussed in depth;
5 Research on DART ionization mechanism: It is found that different working gases (helium, argon, nitrogen, etc.) have different characteristics due to their different ionization energies and the vibrational freedom of nitrogen, which makes them exhibit different characteristics in the ionization process. Although helium has a wider range of applications due to higher ionization energy, in some cases, less argon and nitrogen (lower than helium) produced by the ionization energy produce fewer fragments of the test compound, and then introduce it appropriately. The make up reagent can effectively increase the sensitivity of the analyte. It has been found that fluorobenzene and acetone with lower ionization energy can be used as auxiliary reagents to significantly improve the analytical sensitivity of the analyte.
3. Summary and Outlook <br> The safety and effectiveness of Chinese medicine quality depends mainly on the medicinal ingredients and impurities contained in it. This requires the application of fast and reliable analytical methods to evaluate and control the quality of Chinese herbal medicines. At present, a variety of open ionization mass spectrometry techniques have been successfully applied to the detection of various types of chemical components in a variety of traditional Chinese medicines, and comprehensive evaluation and quality control of the quality of various traditional Chinese medicines. In general, for components with higher volatility or higher proton affinity, such as alkaloids, flavonoids, etc., ionization can occur directly near the surface of plant tissue without the need for solvents and other matrices. In order to obtain good analytical results, solvent-assisted components such as saponins are required, and analysis of saccharide components requires even simple derivatization. One of the principles of open ionization sources is the gas phase ion-molecule reaction around the analyte. These reactions are difficult to achieve the classical closed CI source equilibrium conditions. Therefore, there are some difficulties in experimental conditions and data repeatability. It is still necessary to continuously improve the technology itself. In addition, accurate methods for the quantification of analytes are yet to be developed and improved. These problems require the continuous attention and research of analytical chemists and mass spectrometers. It is believed that in the near future, the analytical methods combining open ionization technology and small mass spectrometry instruments can be applied to the field production and finished drug production lines of traditional Chinese medicine production. More traditional Chinese medicine fields, such as the aid of Chinese medicine diagnosis, play a greater role in promoting the modern development of traditional Chinese medicine.
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