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A new method was proposed for point-of-care testing (POCT) of immunosuppressants in blood using thin-layer paper spray ionization and a miniature mass spectrometer. The aluminum thin-layer plate was used as paper spray substrate, and cut into an equilateral triangle. Aliquots of 10 μL blood sample were loaded on the aluminum thin-layer plate, and then 20 μL methanol was dropped as elution/spray solvent. The tip of the triangular plate was placed 1.0 cm in front of the discontinuous atmospheric pressure interface (DAPI) of the miniature mass spectrometer. When the spray voltage was applied, the sample was eluted from the triangular plate and formed paper spray ionization at the tip. Coupled with the miniature mass spectrometer, five immunosuppressants were detected under negative ion mode. The precursor ions ［M-H］- of tacrolimus, sirolimus, everolimus, ciclosporin A, and mycophenolic acid are m/z 802.6, 912.6, 957.1, 1 200.8, 319.1, and product ions are m/z 560.2 and 604.3, m/z 590.3 and 321.2, m/z 590.3 and 365.2, m/z 1 088.8, m/z 287.4 and 275.1, respectively. Based on the observed signal-to-noise ratio (S/N) of the most intense tandem mass spectrometry (MS/MS) fragment peaks and using the S/N=3 and 10 as the criteria, the limits of detection (LODs) and quantitation (LOQs) are estimated to be 0.5-5 mg/L and 1-10 mg/L, respectively. The internal standard method was used for quantitative analysis, and indapamide was used as the internal standard compound. Sufficient linearity for each analyte is obtained with the correlation coefficients (r) greater than 0.99. The proposed method displays good recoveries in the range of 91.0%-114.3% with the relative standard deviations (RSDs) less than 8.4%. Moreover, the developed method was used for the analysis of blood samples, which spiked with tacrolimus, sirolimus, everolimus, cyclosporine A and mycophenolic acid at the concentration of 100 mg/L. The analytical results demonstrated the consistency between the proposed method and the traditional liquid chromatography-mass spectrometry (LC-MS) method. The entire analysis procedure can be completed within 1 min. The proposed method is simple, fast, accurate, efficient, and suitable for POCT of immunosuppressants in blood.

Naturally-occurring precipitate of traditional Chinese medicine (TCM) is generally considered to be a common phenomenon. The formation of naturally-occurring precipitate originates from the interactions among different chemical components during the decoction process. Previous literature has reported the existence of naturally-occurring precipitate in Sini decoction. In this study, seven pairs of acid-base non-covalent complexes in Sini decoction were characterized using cold spray ionization-mass spectrometry (CSI-MS). The CSI device was built in house, where a stream of nitrogen gas was cooled by liquid nitrogen and used as the sheath gas, providing low-temperature ionization conditions for the MS analysis of the acid-base non-covalent complexes. The gas pipeline was equipped with a valve to regulate the nitrogen flow rate. Data acquisition was carried out using a quadrupole/Orbitrap high-resolution mass spectrometer operated in both full-scan MS and collision-induced dissociation MS/MS modes. Experimental results showed that the seven pairs of acid-base non-covalent complexes were unequivocally observed in positive and negative ionization modes. Mass spectrometric responses for each acid-base non-covalent complex varied with different chemical structures, binding abilities and ionization efficiencies. A representative pair of acid-base non-covalent complex (enoxolone/benzoylmesaconine) was selected to investigate the influence of the acid-base concentration ratio (3∶1, 2∶1, 3∶2, 1∶1, 2∶3, 1∶2, 1∶3) on the binding stoichiometry. The enoxolone/benzoylmesaconine complexes with the binding ratios of 1∶1, 1∶2, 2∶1 were observed, among which the mass spectrometric peak of the 1∶1 binding ratio was the most intensive. The non-covalent interactions of the representative enoxolone/benzoylmesaconine complex were analyzed using isothermal titration calorimetry (ITC) and computational chemistry. The thermodynamic parameters were obtained in the ITC experiment. In comparison with entropy change, the contribution of enthalpy change to Gibbs free energy was more significant, indicating that Van der Waals force and hydrogen bonding might be the main driving force in the formation of acid-base non-covalent complexes. This result was further confirmed by the docking model and simulation results of computational chemistry. Multiple hydrogen bonds derived from the interactions between specific atoms locating in the acid and base compounds promoted the self-assembly process. Moreover, Van der Waals attraction or repulsion force was generated between the C and H atoms at different positions, which in conjunction with hydrogen bonding interaction drove the formation of the acid-base non-covalent complexes. This study provides theoretical foundation and technical instruction for exploring the formation mechanism of naturally-occurring precipitate in Sini decoction.

Due to the high viscosity and bulk complexity of crude oil samples, it poses a grand challenge to determine hydrogen sulfide (H2S) in them. Although many methods have been developed for the analysis of H2S in complex systems, these methods generally have complex processes, large analysis error and low sensitivity. In the study, based on the reaction between triazine and H2S by generating thiadiazine, a small volume of complex crude oil sample was introduced directly into a triazine solution using acetonitrile as solvent for transferring H2S into detectable species by organic mass spectrometry. The experimental parameters of solution composition, acetic acid content, reaction time and reaction temperature were optimized, and the method of paper spray ionization-mass spectrometry (PSI-MS) was established for rapid analysis of H2S in complex crude oil samples. An optimal performance was achieved when the reaction of triazine and H2S was carried out at 30 ℃ for 2 h with acetonitrile containing 0.1% acetic acid as solvent. The standard curve for the quantitative analysis of H2S was constructed according to the linear relationship between MS signal intensity of resulting thiadiazine and the concentration of H2S, which was applied for actual crude oil samples from different sources. The results showed that the linear range and the limit of detection (LOD) were 0.1-1 000 μg/L and 0.041 μg/L with intra-day precision of 3.04% and inter-day precision of 3.18%, respectively. The PSI-MS was also employed to determine H2S in different actual crude oil samples, and the spiked recovery was 91.7%-103.5% with relative standard deviation (RSD) of 1.2%-4.5%. This method has the advantages of easy operation, low cost, high sensitivity and less contamination to mass spectrometer, which is promising for the direct and fast analysis of H2S in complex crude oil samples.

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Particle size and chemical composition are the basic parameters of nanomaterials. The nanoscale size endows nanomaterials with special properties different from bulk materials, such as surface and interface effect, small size effect, quantum size effect, macroscopic quantum tunneling effect and dielectric confinement effect. The type and content of chemical components determine the chemical properties of nanomaterials, such as chemical activity, catalytic selectivity, adsorption selectivity and biological affinity. To a large extent, particle size and chemical composition determine the application of nanomaterials in energy, electronics, environment, sensing, biomedicine and other fields. Therefore, the particle size and composition analysis of nanomaterials are of great significance for the optimization and application of their preparation process. Mass spectrometry is one of the main analytical techniques, which is used to detect the mass, elemental composition and chemical structure of particles or molecules, and it can analyze almost all types and forms of materials, with the characteristics of high analysis accuracy and high detection sensitivity. It has been more widely applied in nano-coating thickness analysis, nanomaterials composition analysis, trace impurity analysis and composition distribution analysis. In some recent research studies, mass spectrometry has also been used to analyze the number concentration, particle size and particle size distribution of nanoparticles, demonstrating its potential for particle size measurements in suspensions over a large size range. In this paper, the advances in studies on mass spectrometry in the analysis of the composition and particle size of nanomaterials were reviewed. The basic principles, advantages and disadvantages, range of application and application cases of inductively coupled plasma mass spectrometry, glow discharge mass spectrometry, secondary ion mass spectrometry and matrix-assisted laser desorption ionization mass spectrometry techniques applicable to the analysis of nanomaterials were introduced, demonstrating the potential of mass spectrometry in the characterization of nanomaterials. Finally, this paper summarized the challenges faced by mass spectrometry analysis technology in environmental interference, size characterization of particles with complex morphology, spatial resolution of components and insitu analysis. The strategies to overcome the above problems by designing special instruments for characterization of nanomaterials and combining with other separation and detection techniques were proposed, trying to provide some reference for the development of mass spectrometry characterization techniques of nanomaterials.

The mass analyzer based on quadrupole field theory, including quadrupole and ion trap, control and screen ions by a non-magnetic, alternating electric field, which was the first proposed by Professor Paul in 1953. Since the birth of quadrupole, ion trap and other related mass spectrometry technologies have been developed relatively maturely, which have made a significant impact and contribution to mass spectrometry. This paper deduced and interpretd the complete physical and mathematical formulae of the design and generation process of the quadrupole field. The process of obtaining the potential distribution of the quadrupole field, the obtaining process of boundary conditions such as electrode shape and voltage on the electrode, and the process of deducing the quadrupole structure and ion trap structure according to the potential distribution of the quadrupole field were discussed. In the above processes, for the purpose of binding ions, a general potential (Prof. Paul called it “allgemeinste potential” in German) distribution equation was obtained by introducing a simple harmonic motion model. And then, according to the basic laws of electromagnetic field and Maxwell’s equation, the condition of zero electric field divergence was introduced. Based on this, through the discussion of the two simplest solutions and boundary conditions, the structure and field distribution equations of the quadrupole and the ion trap were obtained, respectively. This content was an important supplement to the elaboration on the theory of quadrupole field mass spectrometry, which was helpful for a deeper understanding of basic principles of quadrupole field. At the same time, this paper provided a potential mass analyzer design method. Firstly, the design began with the conception of the state of ion motion, and then a force that could control the movement of ions according to the idea was found. Secondly, combined with the basic laws of electromagnetic fields, the general equation and its limiting conditions for the potential distribution that could form this force were obtained. Thirdly, according to the easy-to-operate settings in practice, the boundary conditions of the field (such as electrode shape, electrode voltage, etc.) were obtained, and the intermediate variables in the general equation were replaced with these operable physical parameters. At last, according to the potential distribution equation, the ion motion equation was calculated, and the mathematical relationship between the mass-to-charge ratio and the controllable physical parameters was found. And finally, a mass analysis method for controlling and separating ions was obtained. This kind of design method has important reference significance for theoretical research and original innovation research related to mass spectrometry.

Gunpowder is one of the four great inventions of ancient China, which once had an important impact on the world pattern and development process. However, after the late Ming Dynasty and the early Qing Dynasty, gunpowder firearms gradually declined in China. Gunpowder moved to the West with the war and became black powder, which promoted the birth and development of modern chemical science. The development of chemical science is of great significance to the dynamite family. The brilliant achievements of China's modern king of dynamite revitalize the glory of Chinese gunpowder. This paper reviews the legendary development course and the groundbreaking role of dynamite, describes the properties, rich types and unique working principles of its special chemical energy, and tries to trace the internal mechanism of gunpowder combustion and explosion. It aims to highlight the importance of scientific thinking mode and the development of chemistry discipline to the study of explosives, so as to continuously enrich the knowledge connotation of chemistry students, stimulate their enthusiasm for innovative thinking, enhance their professional confidence, cultural confidence and national confidence, and promote the spirit of scientists. [ABSTRACT FROM AUTHOR]

Study of chemical properties of water radical cations is of great significance for elucidating related reactions process. In this paper, the reaction characteristics of (H2O)2+• prepared online with several benzene derivatives were investigated. The results showed that, when (H2O)2+• reacted with aromatic compounds without electron-withdrawing groups, such as benzene (C6H6, 78 u), anisole (C7H8O, 108 u) and 2,4-dimethylaniline (C8H11N, 121 u), the corresponding phenol product ((C6H5OH) +•, m/z 94), (C7H7O−OH)+•, m/z 124) and (C8H10NOH+H)+, m/z 138)) were observed, accompanied with the production of electron transfer (ET) products (C6H6) +•, (C7H8O) +•) or proton transfer (PT) product ((C8H11N+H)+). Isotope labeling experiments proved that OH in corresponding phenol products was originated from (H2O)2+•. Interestingly, when (H2O)2+• reacted with substituted benzenes bearing strong electron-withdrawing group, such as benzonitrile (C6H5CN, 103 u) and nitrobenzene (C6H5NO2, 123 u), the main products were the radical substituted adducts (C6H5CN+ H2O)+• (m/z 121) and (C6H5NO2+H2O)+• (m/z 141), respectively, without phenol products or substituted benzene radical cation were noticed. It was obvious that the reaction between (H2O)2+• and the substrate occurred through four competing processes: (a) electron transfer (ET) reaction, in which aromatic compounds release an electron to (H2O)2+• to from an aromatic radical cation; (b) proton transfer (PT) reaction in which aromatic compounds got a proton derived from the dissociation of (H2O)2+•; (c) dissociative electron transfer (DET) reaction, accompanied with the electron transfer process, C−H bond cleavage and C−OH bond formation; (d) radical substitution reaction in which a radical cation adduct consisting of aromatic molecule and H2O generates. It was speculated that the diverse reactivity of (H2O)2+• was owe to its two interchange structures ((H2O)H+−•OH and [H2O∴OH2]+•) generates. It was proposed that the electron withdrawing groups on the aromatic ring would benefit for the existence of two-center and three-electron structure of (H2O)2+• and induced the radical substitution reaction. In contrary, compounds without electron withdrawing groups or bearing electron donating groups on the aromatic ring would contribute to the presence of proton transfer structure of (H2O)2+• (containing H+ and •OH) and facilitate the C−OH bond formation. This study will help to elucidate the chemical reaction processes involving benzene or substituted benzenes and (H2O)2+•.

Quadrupole mass spectrometer is currently one of the most widely used small-scale mass spectrometry instruments. Studying the ions trajectory in a quadrupole field is very important for a deeper understanding of the behavior of ions in quadrupole field, which not only helps to propose new scientific and technological issues in mass spectrometry, but also has practical guidance for the development of instruments. The digital simulation of ions trajectory is an efficient mean for studying the motion of ions in quadrupole field. In this paper, a digital simulation model of quadrupole field, namely Sim-Quaq-COM-V1.0, was established based on COMSOL Multiphysics. The simulation results of the model are in good agreement with the theoretical calculation results, and it can be used as an accurate digital model to study the behavior of ions in quadrupole fields. On this basis, the motion behavior of ions in the hyperbolic quadrupole and the cylindrical quadrupole were compared, and the number of m/z 69 ions passing through the hyperbolic quadrupole field is about 4 times that of the cylindrical quadrupole field under the same conditions. The model has three advantages. Firstly, the self-designed general geometric model and grid were adopted as the built-in model, which can be used to simulate the cylindrical quadrupole field and hyperbolic quadrupole field of various geometric sizes. The modular design is simple and clear. Users only need to modify the geometric parameters and mesh parameters to generate the corresponding geometric model and high-precision mesh. Secondly, the parameters of the model could be configured uniformly in a text file, and the model parameters could be adjusted in batches by modifying the text file. Lastly, the function of multi-core and cluster in COMSOL were utilized to achieve large-scale parallel computing through multi-CPU server and quickly process a large number of ions at the same time. Compared with other models like the default COMSOL model for cylindrical quadrupole field, the simulation speed and accuracy of this model are improved. Through the simulation calculation model, the time of geometric design and modeling is saved, the global parameters can be quickly configured, and the difficulty of calculation is reduced. The model supports parallel computing technology. It is greatly improved in terms of calculation speed and calculation amount, thus can process a large number of ions at the same time, shorten the research cycle, and help the digital development of mass spectrometer design and research technology.

Protein content in food is an important indicator of the nutritional value of food, and it is also related to food safety and many other issues, therefore it is significant to accurately determine the protein content for the valuation of food nutrition and safety. The main elements in food include carbon, nitrogen, hydrogen and sulphur, of which nitrogen mainly comes from protein. The average nitrogen content in protein is 16%, so the conversion factor for “nitrogen-to-protein” is 6.25. Therefore, the protein content in food can be obtained by measuring the nitrogen content of food combined with “nitrogen-to-protein” conversion factor. The traditional methods of protein detection are Kjeldahl method, spectrophotometry, and Dumas combustion. The Kjeldahl method is time-consuming and consumes a large amount of reagents, which can cause environmental pollution. Spectrophotometry is susceptible to interference and the quantitative curve is not easy to draw. Dumas combustion is expensive in terms of consumables. In this paper, a platform of tube furnace-quadrupole mass spectrometer was set up to analyze the protein content in food. Food samples were heated at high temperatures in a tube furnace and combusted in an oxygen-rich environment. After the gas products were ionized, they were directly introduced into a quadrupole mass analyzer for detection, which eliminated the need for processes such as oxidation-reduction, adsorption-desorption by using the selection ion scan function of the mass spectrometer. Five kinds of food samples with different protein contents were selected as research object. Each food sample was weighed at 1 g. The food samples were fully combusted in tube furnace at high temperature (1 300 ℃). The gas products were infused through a drying and filtering tube to remove water and smoke, and then entered the EI ion source through a capillary for ionization. By electronic ionization, nitrogen element characteristic ions, N+, NO+, and NO2+ are generated. The peak intensity of the NO2+ ions were detected by the selection ion scan function of the quadrupole mass analyzer. A standard curve for nitrogen quantification is plotted to be y=115.64x+1 896.9 with the correlation coefficient (R2) of 0.99992 and the relative standard deviation (RSD) of 2.1%-6.1%. The nitrogen content can be calculated by using the peak intensity of NO2+ ions according to the standard curve. The experimental platform of tube furnace-mass spectrometer provides a green, rapid, accurate, and low-cost detection method for quantitative analysis of protein content in food.

A method of gas chromatography-mass spectrometry (GC-MS) was established to determine the migration of dibutyl sebacate, dioctyl sebacate, diisooctyl sebacate, decanedioic acid bis(2,2,6,6-tetramethyl-4-piperidinyl)ester in water-based, acidic and alcoholic food simulants, and olive oil and chemical alternative solvents. The 95% ethanol and isooctane chemical substitution solutions were directly analyzed by GC-MS. The olive oil samples were extracted with acetonitrile followed by QuEChERS purification, and then analyzed by GC-MS. Other simulants (water, 4% acetic acid, 10% ethanol, 20% ethanol, and 50% ethanol) were extracted with n-hexane and then determined by GC-MS. The results showed that the method is well performed under optimized conditions, with the correlation coefficient (r2) greater than 0.995. The limits of detection and the limits of quantitation of the four sebacic acid ester compounds in water, 4% acetic acid, 10% ethanol, 20% ethanol, 50% ethanol, 95% ethanol, isooctane, and olive oil simulants are 0.1-0.2 mg/kg, 0.3-0.5 mg/kg, respectively. Migration experiments on plastic samples were conducted, and spiking experiments at three concentration levels of 0.30, 2.0, 4.0 mg/kg in water, 4% acetic acid, 10% ethanol, 20% ethanol, 50% ethanol, 95% ethanol, and isooctane food simulants, and three concentration levels of 0.50, 2.0, 4.0 mg/kg in olive oil food simulants were carried out. The spiking recoveries range from 92.5% to 108%, and the relative standard deviations (RSDs) are 2.4%-8.8%. The method solves the problem that decanedioic acid bis(2,2,6,6-tetramethyl-4-piperidinyl)ester cannot be extracted into n-hexane in 4% acetic acid by adjusting pH value using ammonium hydroxide, the optimal pH range was determined by comparing the responses of four targets at different pH values. QuEChERS was firstly used for migration experiments of sebacic acid esters in food contact materials to solve the turbidity and partial oil precipitation of olive oil simulants in the concentration process after extraction. By optimizing the QuEChERS filling material, the interference of organic acids, fatty acids, sugar and other impurities on the targets were reduced, producing greater separation effect of the targets. The separation efficiency of four chromatographic columns with different polarity was compared, and the DB-17HT column was selected to detect the four sebacic acid esters simultaneously. Plastics such as polypropylene, polyethylene terephthalic acid terephthalate, polyvinyl chloride, composite membranes, paper cups, recycled PET and recycled PVC were collected and migration experiments were carried out, the migration of sebacic acid esters in these plastics materials was investigated. This method is highly sensitive, precise, and accurate, fully meeting the requirement for determining the migration of the sebacic acid esters in food contact materials and their products.

Disulfide bond in protein is an important post translational modification and it is extremely essential for stabilizing the three dimensional structure of proteins, maintaining the correct folded conformation and regulating their biological activities. Therefore, disulfide bonds assignment is of importance to understand life process and to develop protein pharmaceutical. Mass spectrometry technology can serve not only as a means cleaving the disulfide bonds, but also as an analysis tool assigning disulfide bonds connectivity. As a fragmentation means, mass spectrometry has various of MS/MS fragmentation modes. As a detector, it has the advantages of high sensitivity and high accuracy for mass spectrometry information. With these merits, mass spectrometry could fulfill the desire in the characterization of disulfide bonds. This paper summarized the mass spectrometric methods for locating disulfide bonds in proteins or peptides, according to the medium where the disulfide bonds were broken and the cleavage mechanism. Two cleavage mediums (solution and gas phase) were divided. According to the cleavage mechanism, reduction/oxidation reaction using chemical reagents, electrochemical reduction based on electrode reaction, and post column reduction were classified, in which disulfide bonds were cleaved in solution and the mass spectrometer was mainly used as an analysis tool. Meanwhile, molecular collision fragmentation including CID and HCD, electrons capture fragmentation (ECD and ETD), photons absorption fragmentation (e.g. MALDI-ISD and UVPD), and cleavage based on ion ion reactions were summarized, in which disulfide bonds were cleaved in gas phase. For these methods, mass spectrometer was used not only as an analysis tool but also more importantly as a cleavage approach. This review included most disulfide bonds assignment methods and would facilitate bioinformatics related researchers to choose an appropriate mass spectrometric method. Additionally, at the end of this paper, several new challenges in the field of disulfide bond assignment were put forward such as the characterization of multiple disulfide bonds in a short peptide, insufficient study of the disulfide bond artifacts, and the new methods based on novel instruments like UVPD. Moreover, in terms of methodological study, it would be promoted by the development of the new ionization and fragmentation technique producing new kinds of characteristic ions and corresponding data processingtools emerged in the future. Through this review, it was expected to develop more effective mass spectrometric methods for disulfide bonds characterization.

Chemical key laboratory is a special chemical laboratory, it is characterized by complex personnel, big personnel mobility and more expensive large instruments, so the safety management is much difficult. This paper focuses on the safety management of chemical key laboratory, including the safety of chemicals, the safety of instruments and the safety of water and electricity. Combining with the situation of key laboratory where the authors work, the paper proposes specific measurements of safety management from four aspects: safety consciousness, security system, hardware construction and software management. [ABSTRACT FROM AUTHOR]

Residual host cell proteins (HCPs) can significantly impact the efficacy and safety of biologics, and are considered as critical quality attributes that require rigorous quality control. Currently, the enzyme-linked immunosorbent assay (ELISA) is the most common methodology for monitoring residual HCPs in biologics. However, the accuracy of ELISA is highly dependent on the specificity of the used antibodies, and it does not provide informations about the types and quantities of individual HCP, making it necessary to complement ELISA with other analytical methods. Mass spectrometry (MS) has emerged as key analytical and characterization technique for HCPs analysis. Without solely depending on antibody affinity recognition, MS enables the identification and quantification of individual HCP, which facilitates a deeper understanding of HCP profiles, clearance patterns, risk assessment, and problematic HCP monitoring. Moreover, the method of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) offers faster development for new products. Despite its advantages, LC-MS/MS faces challenges in HCP analysis, such as the lack of standardized procedures and validation standards, signal suppression in the presence of high-abundance active pharmaceutical ingredient (API), and the high instrumentation cost and specialized expertise barriers in routine quality control settings. Researchers and industry experts are working towards establishing standardized procedures and validation guidelines for HCPs analysis using LC-MS/MS, which includes utilizing data dependent acquisition (DDA) for the construction of project-specific HCP libraries, data independent acquisition (DIA) for efficient HCP screening, and targeted strategy like multiple reaction monitoring (MRM) for absolute quantification of high-risk HCPs. Efforts are also underway to mitigate signal suppression effects and reduce instrumentation costs. To overcome high-abundance API interference in HCP detection, advanced techniques involving API-HCP separation, HCP enrichment, and non-denaturing enzymatic digestion have been developed, allowing for the monitoring of HCPs at exceptionally low levels (0.1 to 0.01 ppm). This paper provided an overview of MS-based HCPs analysis workflow utilized "proteomics" approach, covering essential considerations in instrument selection, sample preparation, LC separation, MS data acquisition, and data analysis and reporting, corresponding optimized practices were discussed. Nowadays ELISA is still a workhorse for residual HCP analysis, however, LC-MS/MS is a valuable tool for the analysis of residual HCPs in biologics. It offers a more comprehensive and detailed view of HCP profiles and their clearance patterns throughout the production process, enabling better risk assessment and monitoring of problematic HCPs. While challenges remain, ongoing research and development efforts are paving the way for the broader adoption of LC-MS/MS in the biopharmaceutical industry, ultimately ensuring the quality and safety of biologic products.

Copper (Cu) is a crucial trace metal element in human body, which plays an important role in many life processes. Meanwhile, copper is strictly regulated in the human body and its homeostasis is closely related to the physiological state. The occurrences of many diseases are often accompanied by the copper imbalance. By monitoring the subtle variation in copper homeostasis, it can more accurately identify the factors that lead to abnormal changes in human physiology, especially the impact of environmental factors on the occurrence and development of diseases. In the past two decades, with the development of analytical instruments and improvement of analytical methods, non-traditional stable isotopic analysis has been widely applied in geochemistry and archaeology. Owing to its strong traceability, non-traditional stable isotopic analysis can also provide a new perspective to reveal the mechanisms of element homeostasis imbalance. Especially, stable copper isotopic analysis has a wide application prospect in environmental health research. Because of the virtues of wide application range and high analytical accuracy, multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has effectively promoted the process of copper isotopic analysis. In this paper, we reviewed the mechanisms of non-traditional stable isotope fractionation and analysis methods of Cu isotopes based on MC-ICP-MS, and the basic conception of mass dependent fractionation (MDF) and non-mass dependent fractionation (MIF) as well as the instrumental configuration of MC-ICP-MS. We also introduced the methods of copper isotopic analysis, and then summarized the main applications of copper isotopic analysis in environmental health research. We focused on two aspects, i.e., Cu isotopic analysis of population characteristics and research on disease indicators. In summarizing the relevant researches of Cu isotopic analysis of population characteristics, we reviewed the influence factors, such as age, gender, dietary habits, and other factors. Afterwards, the studies of copper isotopic analysis on some diseases, such as cancers, nervous diseases, disorders of copper transporters, and other diseases were summarized. Finally, we discussed the application prospects of copper isotopic analysis in environmental health research. Until now, the application of stable copper isotopic analysis in environmental health is still in the initial stage, and there still exist many difficulties and challenges. We primarily list four main difficulties and challenges in future studies, including high-throughput sample analysis, background population investigation, combination of other clinical indicators, and combination of multiple omics techniques.

Volatile organic compounds (VOCs) have been widely studied as potential biomarkers of cancer cells. Currently, in vitro cells are mostly cultured in two-dimensional (2D) adherent mode, which is different from in vivo tumor cells with three-dimensional structures. Tumor cell spheres cultured in three-dimensional mode have many similar characteristics to those of in vivo tumors, such as: 1) the structure of cell spheres is divided into proliferative, quiescent, and hypoxic zones; 2) the extracellular matrix deposited in the cell spheres not only increases the density of the spheres but also affects the tumor progression by intercellular interactions. In addition, VOCs detection is mainly accomplished by gas chromatography-mass spectrometry (GC-MS) combined with solid-phase microextraction (SPME), which permits both qualitative and quantitative analysis of VOCs. In this present work, lung cancer cells A549 and lung epithelial cells BEAS-2B were respectively taken as examples to construct three-dimensional (3D) culture models, and 2D models and culture media were used as controls. The VOCs released from cells were detected by SPME-GC-MS. Totally, 163 VOC chromatographic peaks were included in the statistical analyses using an untargeted strategy. Based on orthogonal partial least squares discriminant analysis (OPLS-DA) with the combined criteria of Mann-Whitney U test (p2), differential VOCs released by cells in 2D and 3D culture modes were screened out. There were four VOCs of acetic acid, 1-pyrroline, 4-methylheptane and 2,4-dimethyl-1-heptene released at differential levels from A549 cells cultured under 2D and 3D modes, and four VOCs of ethanol, 1-pyrroline, 4-methylheptane and 2,4-dimethyl-1-heptene released at various amounts from BEAS-2B cells cultured under 2D and 3D modes, respectively. In comparison to 2D models, 3D models released 2.11 to 12.81 times more of these VOCs. Afterwards, the possible biochemical sources of the differentially released VOCs and the possible mechanisms for the differences in the releases of VOCs in the 2D/3D models were discussed. These differentially released VOCs have been reported to be potential markers in lung cancer cells, liver cancer cells, and other biological samples in previous studies. In addition, compared to 2D models, 3D models can better simulate tumor growth in vivo as well as cellular microenvironments, including the creation of reactive oxygen species (ROS) and extracellular matrix deposition. These physiological microenvironments may promote the release of cellularly differential VOCs. In this paper, by constructing 3D cell models and analyzing differential changes in cellular VOCs, it was proved that 3D culture has a broad application prospect in the detection of cellular VOCs in vitro, and is expected to be a valuable research platform for cancer biomarker screening.

Khat is a kind of common drug plant. Many experiments have shown that the content of cathinone norpseudoephedrine and norephedrine in some varieties of Khat are similar. However, some studies showed that there are differences in the intensity of psychoactivity between these varieties. Therefore, it is speculated that other substances in Khat may affect the psychoactive strength of Khat. But currently there are some difficulties in non-targeted screening of unknown compounds without mass spectrometry database information and standard solutions. In this paper, the unknown cathinone alkaloids in Khat were discovered and resolved by HPLC-Q-TOF MS in-source fragmentation multistage mass spectrometry. The separation was carried out on a ZORBAX Eclipse Plus Phenyl-Hexyl column (3.0 mm×100 mm×1.8 μm) with a gradient elution using 0.1% formic acid in water (A)-acetonitrile (B) as the mobile phase. The mobile phase flow rate was 0.3 mL/min, and the column temperature was 30 ℃. The screening of unknown cathinone alkaloid components was realized by the in-source cleavage characteristics of cathinone alkaloids in single-stage mass spectrometry under full-scan mode using an ESI ion source, and then the molecular structures of the unknown cathinone alkaloid components were deduced from the multi-stage MS cleavage patterns of the unknown cathinone alkaloid components in the target ion acquisition mode. The results showed that this method can effectively realize the screening and resolution of the unknown alkaloid components in Khat. A total of three cathinone alkaloid components, including methcathinone, ethcathinone and 2-amino-1-phenyl-1-butanone, were identified in Khat. Methcathinone and ethcathinone were corroborated using standard substances, and 2-amino-1-phenyl-1-butanone needs to be further corroborated due to the lack of corresponding standard substances. The work provides a guideline for the further study of the psychoactive components in Khat, and a reference for the analysis of unknown compounds in other fields.

The study of catalytic reaction mechanism is a critical and extremely challenging project. Online monitoring of reactants, intermediates and products during catalytic reactions can provide key evidence for the in-depth study of complex catalytic reaction networks, reaction pathways and reaction kinetics. As an online mass spectrometry based on soft ionization technique, vacuum ultraviolet photoionization mass spectrometry (VUV-PIMS) has proven itself as a versatile and powerful analytical technique for online and real-time process monitoring, which has gradually become a highly concerned characterization technique for catalytic reaction processes due to its advantages of high molecular ion yield, simple spectrum interpretation and high sensitivity. Compared with other commonly used synchrotron radiation and laser-based VUV light sources, the low pressure discharge lamps filled with various rare gases are compact, easy to operate, and low cost, such as krypton discharge lamps. However, the relatively low photon intensity of these lamps limits their applications. The efforts have been taken to develop stronger VUV light sources or lamp-based efficient combined ion sources to solve this issue. In this paper, the development of VUV-PIMS technology, especially the research progress of photoionization ion sources based on the VUV lamp, were reviewed, such as high-pressure photoionization (HPPI) source, single photon ionization-photoelectron ionization (SPI-PEI) combined ion source, and single photon ionization-chemical ionization (SPI-CI) combined ion source. By combining capillary sampling technology or molecular beam sampling technology, the applications of VUV-PIMS for real-time and online monitoring of stable products and active intermediates in catalytic processes were introduced, such as ammonia synthesis, methane/ethane catalytic conversion, methanol to olefins. The applications in online monitoring of these catalytic reaction processes exhibited an excellent performance and wide potential applications of VUV-PIMS in process monitoring and reaction mechanism research. Finally, the future development trend of VUV-PIMS was prospected for the application requirements of accurate characterization of catalytic reaction process.

Metal nanoclusters (NCs) are stable aggregates at the molecular level, consisting of several to hundreds of metal atoms bound together by physical or chemical interaction. These nanoclusters exhibit unique physicochemical properties that have garnered significant attention in various fields, including biology, catalysis, sensing, and drug delivery. In the field of catalytic reactions, atomically precise metal nanoclusters have acted as an archetypical model for elucidating the structural evolution and structure-property relationship of nanomaterials. However, due to the factors such as the uncertainty of the growth mechanism, the complexity of the crystallization process, and the inherent poor stability, the cluster research faces some challenges in the precise synthesis, structural analysis as well as the comprehension of catalytic reaction mechanism which hinder the full exploration and understanding of these fascinating properties of clusters. Recent years, mass spectrometry (MS) has emerged as a crucial tool in biomolecular analysis and the detection of organic reaction intermediates due to its high sensitivity, high resolution, and fast response. In cluster chemistry, the researchers have also introduced this technique into the study of metal nanoclusters with precise atomic numbers, which have played an important role in the synthesis of clusters and the analysis of their structures as well as reaction mechanisms. The ion source, as the "heart" of the MS, can ionize the analyte and then be detected by MS. Currently, the main ionization methods used for cluster analysis are electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). These two "soft" ionization techniques can obtain the quasi-molecular ion peaks of the clusters without destroying the structure of the clusters, thus determining the composition of the clusters. In addition, MS enables real-time characterization of the reaction process in solution, allowing for online monitoring of complex reaction components, providing an experimental basis for synthesis processes and catalytic reaction mechanisms of metal clusters. Notably, gas-phase ion-molecule reactions can provide catalytic primitive steps and reaction kinetics enabling in-depth analysis of microscopic reaction mechanisms at a strictly molecular level. For the structural characterization of clusters, tandem mass spectrometry (MS/MS) combined with quantum chemical calculation provides a powerful tool to study and understand the structural evolutions of clusters. By comparing and verifying the experimental and computational results, the correlation between the catalyst structure and its performance can be established, deepening our understanding of the catalytic reaction mechanism and process. This paper was focused on the latest development of soft ionization MS in monitoring intermediates of cluster synthesis, structure analysis, and catalytic reaction mechanism, and the emerging directions in this fascinating area of research were highlighted.

The content of ethanol in wine can affect its quality. Some edible alcohol contains small amounts of methanol, and its accumulation can cause serious health problems. Therefore, it is very important to test the contents of methanol and ethanol in alcohol products. In this paper, a rapid method for the determination of methanol and ethanol by ambient corona discharge ionization mass spectrometry was developed. The method is based on the interaction of water radical cation with methanol and ethanol, respectively. In the positive ion mode, the water dimer radical cation (H2O)2+· (m/z 36) with ambient corona discharge ionization source was prepared by using ambient corona discharge ionization source, and it was introduced into the mass spectrometer with methanol or ethanol through a dual-channel low-energy corona discharge ionization device. The two reacted with each other to form the corresponding water radical cationic complex [CH3OH+H2O]+· (m/z 50) and [CH3CH2OH+H2O]+· (m/z 64), which realized the direct and rapid qualitative and quantitative analysis of methyl alcohol and ethanol in different kinds of alcoholic beverages. The result showed that the limits of detection and the limits of quantification of methanol and ethanol were 0.011 and 0.004 mg/L, 0.038 and 0.014 mg/L, respectively. The correlation coefficients of the target ionic strength curves obtained by the interaction of different concentrations of standard methanol and ethanol with water free radical cation could reach to 0.990 4 and 0.991 1, respectively. By using this method, no methanol was detected in common alcoholic drinks, and the ethanol content in liquor was higher than beer. In the actual work, the method has good practicability through the experimental exploration and verification of different wines. This method does not require sample pretreatment, has the advantages of simple operation and fast analysis, and is especially suitable for the detection of aqueous system. This study has important guiding significance for the quantitative detection and analysis of methanol and ethanol in complex system, provides technical support for the detection of alcoholic beverages and food, and also provides an effective strategy for the quantitative detection of the content of small and medium molecular alcohols in actual samples.

Microdroplets have many unique features such as small size and high electric field, therefore they can be accelerated to initiate chemical reactions and even promote some reactions that cannot be carried out in liquid phase. N, N-Dimethylaniline (DMA) is commonly used in medicine as a raw material for the synthesis of pharmaceutical intermediates. At present, the study involving in the detection of DMA is mainly focused on quantitative detection, and there is few reports on oxidation reaction and gas phase dissociation reaction of DMA. In this paper, the oxidation behavior and dissociation reaction of DMA and related compounds were studied by microdroplet spray mass spectrometry and tandem mass spectrometry. It was found that the ultra-high electric field spontaneously generated by microdroplets at the air-water interface can enable the oxidation reaction of DMA and related compounds to form abundant radical cation DMA+·. By changing the reaction distance, carrier gas pressure, injection velocity, sample concentration and substituent groups, the influence of experimental conditions and substituent modes on the generation of DMA+· was explored. The result showed that the presence of electron donor groups is benefit for the stability of radical cations. After the dissociation of DMA+·, the main product ions were generated by elimination of hydrogen radical and a successive elimination of HC≡N via methyl migration reaction. In addition, when the electron-donating CH3 group was connected with DMA, the intensity of related radical cation increased obviously, indicating that the electron-donating groups promoted the migration reaction. In conclusion, the stable transient intermediate DMA+· that is difficult to prepare by other means, was obtained by microdroplet reaction in this study. This method is helpful to deepen the understanding of the chemical promoted oxidation reaction characteristics of water droplets and enriches the rearrangement reaction types of aniline compounds in gas phase dissociation. It is expected that the prepared active species such as high reactivity radical cations will be applied to chemical industry or pharmaceutical fields in the future.

The development of fragment ion detection is significant for improving the analysis capacity of mass spectrometry. Fragmentation technique has been widely used in the identification of peptides and top-down/bottom-up proteomics analysis. To date, collision-induced dissociation (CID) remains the most commonly used ion activation method in MS/MS experiments, but the effectiveness of CID in ion trap mass spectrometer is limited by low mass truncation and weak fragmentation yield. Recently, technological advances have made the CID process in the ITMS more flexible. The CID process in an ion trap mass spectrometry (ITMS) is usually achieved by superimposing a small auxiliary alternating current (AC) voltage on the main radio frequency (RF) voltage. When the frequency of AC is close to or equal to the lifetime frequency of the isolated ions, the ions are resonantly excited, resulting in a dramatic increase in the kinetic energy of the ions. The high kinetic energy ions will then collide with the background gas, converting the kinetic energy into the internal energy of the ions. Eventually, when the internal energy of the ion is greater than the potential barrier of a bond breaking, a series of fragmentation ions will be formed. In theory, controlling the qvalue is essential to maintain the fragmentation efficiency and trapping efficiency of tandem MS/MS, thus improving the detection of fragmentation ions, while currently reported techniques typically require complex circuitry and often yield different CID modes. In this paper, the effective improvement of fragment ion detection by developing the dipole direct current excitation-collision induced dissociation (DDC-CID) technique was demonstrated, which was implemented on a digital ion trap mass spectrometer by adjusting the duty cycle during CID, or specifically, by increasing the dipole direct current (DC) voltage during CID. The use of pulsed switches and square wave voltages in the digital ion trap technique was a good solution to the problem of circuit design for frequency scanning ion traps. With the DDC-CID technique, the fragmentation efficiency of precursor ions could be improved marginally, with at least 3-fold increase in capture efficiency for low mass fragmentation ions and 1.2-fold increase in fragmentation efficiency for reserpine molecules. These experimental results could also be verified by simulations, where plots of ion trap stability changes indicated changes in ion q-values. In any case, DDC-CID provides an idea and a solution for the low efficiency of fragment ion detection during tandem MS/MS analysis, which will certainly be useful in the future.

Arsenic hazard is severe serious to environment and human health. In recent years, arsenic is paid high concern as a toxic metallic element. This paper summarized the latest research results at home and abroad, deemed that there existed an obvious tendency of arsenic accumulation in arable land in China. The paper also analyzed the natural and anthropogenic sources of arsenic. Meanwhile, this paper systematically introduced the related control measures adopted at present including the physics, chemistry, biology, and agronomy methods, from the angle of removing arsenic from arable land and reducing its effectiveness. Furthermore, this paper prospected the future research direction and hotspots. [ABSTRACT FROM AUTHOR]

Chemistry is an important group of basic courses, while genetics is one of the important major-basic courses in curriculum of many majors in agricultural institutes or universities. In order to establish the linkage between the major course and the basic course, the ability of application of the chemical knowledge previously learned in understanding genetic knowledge in genetics teaching is worthy of discussion for genetics teachers. In this paper, the authors advocate to apply some chemical knowledge previously learned to understand genetic knowledge in genetics teaching with infiltrative model, which could help students learn and understand genetic knowledge more deeply. Analysis of the intrinsic logistic relationship among the knowledge of different courses and construction of the integral knowledge network are useful for students to improve their analytic, comprehensive and logistic abilities. By this way, we could explore a new teaching model to develop the talents with new ideas and comprehensive competence in agricultural fields.

Proteins are the carriers of biological structure and function, which are involved in almost all the physiological processes in organisms. The qualitative and quantitative analysis of proteins can not only help us understand the mechanisms of life activities, but also screen for the proteins with abnormal expression compared to healthy controls as biomarkers of diseases as well as environmental exposure to harmful substances, thus facilitating to unravel the mechanisms of disease generation and development. Tandem mass spectrometry (MS/MS) is currently the main tool for high-throughput proteomics analysis. It can characterize the proteins by determining the molecular mass of digestion products, locating modification sites, and obtaining sequence information. However, acidic amino acid residues often have a significant impact on the cleavage process of peptides, limiting the performance of MS/MS. For example, for the phosphopeptides containing abundance of negatively charged carboxyl and phosphoryl groups, their ionization is not efficient in the positive mode, and neutral loss is easy to occur during the cleavage process, resulting in a low coverage of product ions in the MS/MS spectra. In this paper, the carboxyl groups from the R group of aspartic acid and glutamic acid as well as the C-terminus of peptide were neutralized using dimethylamine derivatization under mild condition. Accordingly, the fragmentation features of peptides with altered charge properties were studied in collision-induced dissociation (CID) mode. Further, the peptides were labeled using light and heavy isotopic dimethylamine, respectively, thus enabling to verify the features based on the same ion with different labels. The results showed that the precursor ion signal from the derivatized peptide was significantly enhanced compared to that of the native peptide. And, the derived peptides could yield a variety of a, b, y, and z ions, and some reported ions in MS/MS analysis, such as the ion at m/z 129.10/135.14 produced by the peptides with glutamic acid or lysine residue at C-terminus, which facilitating to determine the C-terminal amino acid of protein. While, the peptides proned to lose the derivative groups located at the C-terminus, yielding a series of ions at m/z ［yn-45.06］ or ［yn-73.05］. In addition, the neutralization of carboxyl groups could suppress the loss of phosphoryl groups in phosphopeptides to a certain extent, thus improving the resolution efficiency of the MS/MS spectra. Overall, the derivatization method based on carboxy-amidation can provide abundant information for the sequence determination and quantitative analysis of peptides due to the altered fragmentation features in CID mode.

The book of Experiments of Modern Fundamental Chemistry published by Chongqing University Press gives the conditions of B-Z oscillating reaction experiment by using H2 SO4-KBrO3-malonic acid,however,the results are not reasonable: the oscillating signal is not strong and obvious,and the reduce time is quite long. Hence a optimal and improving experimental conditions are presented in this paper. Research results show that the best experimental conditions of concentration of B-Z oscillatory reaction are 0. 40 mol/L of KBrO3,0. 70 mol/L of CH2(COOH)2,2. 00 mol/L of H2 SO4 and 6. 00 mmol/L of Ce4 +. The conditions given in the textbook are 0. 25 mol/L KBrO3,0. 50 mol/L CH2(COOH)2,3. 00 mol/L H2 SO4 and 4. 00 mmol/LCe4 +. By the new conditions,the peak of electromotive force increases by 21. 51%,the induction time decreases by 26. 27%,the oscillation period decreases by 27. 27%,and the teaching effect is obvious. [ABSTRACT FROM AUTHOR]

Efficient removal of dissolved organic matter (DOM) is an important task for wastewater treatment. However, the molecular composition of DOM and its transformation during the treatment are still unclear. In this paper, the organic components in the stream of a coal coking wastewater treatment process were studied. The wastewater was extracted by dichloromethane (CH2Cl2)，the extract was named as ‘oil phase’. Then the raffinate was extracted by solid-phase extraction, the extract was named as ‘water phase’. The ratios of total organic carbon contents (TOC) in the oil and water phase samples were generally consistent during the treatment process. The extracted DOM was characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Eight class species were as assigned from the mass spectra, namely N1O1-7, N2O1-6, N1O5, N1O2-6S1, N2O3-5S1, O2-8, O2-6S1, O4-5S2. The class categories which contain multiple oxygen atoms (Ox) and both multiple oxygen and sulfur atoms (OxSy) were dominant in the oil phase. The relative abundance of each species was decreased sharply after the first aerobic biological process, which was consistent with the TOC rapid decline in the sample. O2-8 compounds existed in all wastewater samples and dominated in the final sample, indicating that these compounds were the most stubborn pollutants which were difficult to remove in all treatment processes. It is speculated that these compounds may come from some humic-acids which have complex structure and multiple oxygen atoms naturally existing in natural water. The composition of O3 class species showed two patterns among the wastewater treatment process, compounds with high double bond equivalent (DBE) were dominant in the first four processes, while a proliferation of low DBE components was observed in the last three samples. It indicated that those low DBE components were generated by the oxidation of other substances, such as O1 and O2 species. The water phase organic matter had an extremely complex molecular composition and a total of 27 different compound class species were identified in a single mass spectrum. Ox, OxS1-2 and NxOyS1-2 were the major class categories in water phase. On the whole, OxS1-2 was much easier than the other two categories to be removed during the wastewater treatment process. In the OxS1-2 class category, O4S1 had a much higher relative abundance than other species. It decreased sharply among the process, but it still accounted for a large proportion in the final process, which implied the O4S1 species had strong resistance to removal. The relative abundances of each species in NxOyS1-2 had consistent composition and transformation, and could be effectively removed after the wastewater treatment process. The composition transformation trend of O6S1 was similar to N1O6S1, those compounds with low DBE value (512) and low carbon number (1020) were dominated after the aerobic biological process section and remained in the final process. The study of DOM in coal coking wastewater treatment from the molecular level by FT-ICR MS will contribute to understand the transformation law of pollutant compounds. However, limited by the mass spectrometry, only the molecular composition information can be obtained. The molecular structure information, especially for the functional groups, is hard to be obtained. In order to research the transformations law of pollutant compounds for further, the structural information needs to be deduced combining the molecular composition, the precursor and the polarity of wastewater pollutants. Developing more efficient and advanced separation and enrichment methods is another way to research the molecular structure information. By the further work, a fully understand of the pollutant composition will be obtained, and a more effective wastewater treatment process will be developed.

Traditional large mass spectrometer has the advantages of high sensitivity and fast speed of analysis. However, because of its large size, it only can be used in professional labs generally. The miniature mass spectrometer has the advantages of lightweight and portable. Although some performances are sacrificed, the needs of the application field of on-site detection were met. The ion trap was used as the mass analyzer for miniature mass spectrometer, because of its good performance and small size. In this paper, two miniature mass spectrometers called “Brick-L” and “Brick-V” were introduced, which were based on the new technologies developed by our lab, including the quadrupole enhanced dipolar resonance ejection from the linear ion trap, the continuous atmospheric pressure interface, and the hybrid ion funnel. Both the miniature mass spectrometers had similar vacuum chamber structures and the same main components, such as ion funnel, mass analyzer and control circuit. The switch between Brick-V and Brick-L could be achieved by simply changing the front board of the chamber where the interface system is located, and it allowed the instruments to meet variable demands of on-site detection more easily. The difference was that the Brick-L required to be coupled with an atmospheric pressure ion source, and it could detect gas, liquid and solid samples. An UV lamp ion source was installed inside the Brick-V, which could detect volatile organic compounds (VOCs). The overall weight of the miniature mass spectrometers is about 20 kg, the size is 38 cm×23 cm×34 cm, the power consumption is 200 W, and they have the capability of MS2. The limits of detection (LODs) of cocaine and imatinib can reach 1 μg/L for Brick-L, and the resolution is more than 1 600. Brick-V can be used to identify fruits. Due to use the continuous atmospheric pressure interface, Brick-V has more resistant to pollution and shorter detection cycle time than the same type of miniature mass spectrometer using the photon ionization source. The two instruments are portable and easy to operate, which can be used in rapid on-site analysis and have good application prospects.

Per- and polyfluoroalkyl substances (PFAS) are a large class of organic compounds, in which all or part of the hydrogen atoms in the alkyl-chain are replaced by fluorine, and many PFAS are used globally in chemicals, leather textile, paper, packaging and other industrial and consumer goods production fields. Many studies have shown that PFAS possesses hepatic and metabolic toxicity, reproductive and developmental toxicity, immunotoxicity, and so on. Therefore, the use of PFAS in textiles has been restricted by lots of regulations or standards world widely, such as the International Ecological Textile Standard (STANDARD 100 by OEKO-TEX®), the Restricted Substances List (RSL) of the American Apparel & Footwear Association (AAFA) and the REACH regulations of EU. However, there is still lack of simultaneous determination method for various volatile PFAS in relevant standards. In this study, a method of gas chromatography-mass spectrometry (GC-MS) was developed for the simultaneous determination of 12 volatile PFAS in infant and child textiles, including four fluorotelomer alcohols (FTOHs), three fluorotelomer acrylates (FTAs), three perfluorooctane sulfonamides (FOSAs) and two perfluorooctane sulfonamidoethanols (FOSEs). The redissolve solvent was optimized, and the extraction efficiencies for different extraction solvents, extraction volumes, extraction times, extraction temperature and time were compared. 20 mL Acetonitrile was selected as extraction solvent, and the sample was extracted twice by ultrasonic at 60 ℃ for 30 min each time, then the combined supernatants were concentrated by rotary evaporation. Finally, the targets were separated by DB-5MS column and detected at selected ion monitor (SIM) mode, and quantified by external standard method. The results showed that 4∶2 FTOH and the other 11 volatile PFAS had good linear relationship in the range of 20-5 000, 10-5 000 μg/L, respectively, and the correlation coefficients (R2) were not less than 0.998. The limits of quantification (LOQs) were 0.03-0.07 mg/kg. The recoveries of 12 PFAS were 71.9%-113.6% under the two spiked levels (levels at the LOQ and the limit content of relevant standards), and the relative standard deviations (RSDs) were 1.2%-12.8% (n=6). The method has the advantages of simple pretreatment, accurate qualitative and quantitative determination, high sensitivity, and good repeatability. The actual samples were divided into two groups and determined by this method. One group included 53 pieces of textile fabrics with certain waterproofness that were tested daily in the laboratory. Some of these textile fabrics have cartoon patterns, which may be used for making children’s clothing. The other group included 26 pieces of infant and child clothes purchased from online stores. The results showed that the positive rate of volatile PFAS in textile fabrics was high. FTOHs and FTAs were detected, and their concentrations were in the range of 0.08-276.41 mg/kg. FOSAs were not detected in the samples. The textile fibers with PFAS detected were mainly polyester. Volatile PFAS were not detected in the randomly purchased infant and child cloth products, which might be mainly because they didn’t have waterproofs. The skin exposure model proposed by the European Chemical Agency was used to assess exposure risks. The mixed exposure of various PFAS in textiles was calculated by the relative potency factor (RPF), which was converted into the equivalent of PFOA, and compared with the safety threshold given by the US Environmental Protection Agency and the European Food Safety Agency. The results showed that the risk of direct health hazards to infants and children from the exposure of detected target substances was low. The method has reference value for the control of volatile PFAS risk substances in baby textiles.

Microplastics are high molecular-weight polymers with micro- or nano-meter size, which have become a major global environmental issue in recent decades due to their ubiquity in the environment, bioavailability and potential toxicity. New analytical methods for the characterization of microplastics and nanoplastics are quickly emerging, such as particle size measurement, component identification and quantification. Many techniques have been developed and applied for the characterization of microplastics, such as Fourier-transform infrared spectroscopy, Raman spectroscopy and mass spectrometry (MS), etc. In recent years, the continuous development of MS technology has drawn more and more attention to the characterization and the environmental impact of microplastics. This paper mainly reviewed the state-of-the-art development and application of MS in microplastics analysis during the past decade. The principles and characteristics of various MS techniques used in the qualitative and quantitative analysis of microplastics were described, including thermal analysis coupled with MS-based techniques, elemental analytical MS, MALDI-ToF MS, LC-MS and ToF-SIMS. MS can provide chemical structure, molecular weight, degree of polymerization, additives, main functional groups and other information about the polymers, so it can be widely applied for chemical characterization, particle size determination and semi-quantitative/quantitative analysis of microplastics of small size. It has the advantages of replicable, fast real-time in situ analysis and high throughput detection, which can not only detect microplastics in the environment but also in biological tissues or cells in situ, showing great application potential in the research on the source, migration, transformation and interaction with biological organisms. The microplastics have been detected in the ocean, atmosphere, soil, consumer products, organisms and even human tissue, including polyethylene, polyamide, polyvinyl chloride, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, etc. The health risks of ingestion of microplastics deserve further exploration, especially nano plastics. The continuous development of MS technique and its combination with other separation/characterization methods will greatly promote the analysis of microplastics, and MS will become a more and more powerful tool in this research field and provide important scientific basis for the control of microplastic pollution.

Atmosphere is a complex mixture system including various gaseous molecules and particulate matters as well as free radicals. The cases of atmospheric pollution often occur in urban or suburban areas during the evolution of industry, and have adverse influences on the human health and daily life. The origins of atmospheric pollution are complicated, which often comprise a series of chemical reactions involving abundant volatile organic compounds (VOCs), free radicals and aerosol particles. How to analyze these species operando is a hot, significant and challenging topic of atmospheric chemistry. In the past decades, benefiting from the rapid development of analytical techniques used in the atmospheric chemistry, abundant reaction mechanisms for the formation of pollutants have been proposed and revealed. However, due to the complexity of atmospheric chemistry, presently the formation mechanisms of atmospheric pollution are still very limited or coarse and deserve to be comprehensively investigated. As a widely used analytical technique, vacuum ultraviolet photoionization mass spectrometry (VUV-PIMS) can provide mass information of molecular ions benefiting from its “soft” ionization at the threshold ionization energy of molecules. Therefore, the obtained VUV photoionization mass spectra have the characters of no or less fragment ions and are easier to be assigned. Then the key chemical components involved in the atmospheric chemical reactions can be identified efficiently, which are very helpful to reveal the complex mechanisms of atmospheric chemical reactions. In this paper, the recent development of VUV-PIMS and its wide applications in atmospheric chemistry were summarized. Several kinds of VUV light sources, including VUV laser, synchrotron radiation, free electron laser and VUV discharge lamp, were presented. In combination with these advanced light sources, several kinds of VUV-PIMS setups were introduced and their advantages were discussed. In addition, the applications of VUVPIMS to analyze atmospheric VOCs, free radicals and their reactions, and the chemical compositions of aerosol particles were reviewed. Concretely, in the aspect to detect VOCs in laboratory or on site, several strategies to improve the sensitivity of detection, in particular the improvement of the photoionization source, were presented here in detail. The analysis of several elusive free radicals and their atmospheric oxidation reactions studied by VUVPIMS were described. Then, the utilization of VUV-PIMS to measure the chemical compositions of aerosols was introduced. Moreover, the perspectives of VUV-PIMS and its further applications in atmospheric chemistry were also discussed.

Antibiotic misuse is becoming a worldwide public health issue due to serious risk to human health and environment. Residual antibiotics in environment mainly come from the wastewater from pharmaceutical factories, aquaculture, animal husbandry and hospitals. Antibiotics are included in the newly published List of Newly Controlled Pollutants (2022 Edition) (Draft for Comments). However, test standards are still lacking. Highly accurate results of the trace amounts of antibiotics distributed in the environment can be obtained by mass spectrometry coupled with chromatography. Nonetheless, sample pretreatment is time-consuming and expert-required. Compared with laboratory detection, ambient miniature mass spectrometry can realize on-site detection of the antibiotics without or with little pretreatment. On-site detection can be used for rapid qualitative and semi-quantitative detection, which can reflect the levels of water body pollution and accurately trace the pollutant sources. On-site detection also can provide technical support for the regulatory governance of antibiotics. But now no-studies have been reported on the on-site detection of environmental antibiotics in the field. It is urgent to develop a rapid detection method for antibiotic residues in the environment to assess antibiotic pollution and provide support for regulation. In this paper, the detection of antibiotics was carried out based on flash desorption and acetone assisted photoionization source miniature ion trap mass spectrometry, the detection parameters of antibiotics were systematically optimized including gas flow and injection time sequence, and a rapid and high throughput detection method of antibiotics was established. The efficiency of thermal desorption was improved using pulse purging mode and halogen lamp flash thermal desorption, and the signal intensities of high boiling point antibiotics were significantly increased. Quantitative detection of antibiotics was realized by isotope internal standard, and preliminary detection of antibiotics in water was carried out. This method does not need complicated pre-processing and can be completed in 1 min. The detection limits of isoniazid (INZ), ethionamide (ETN) and voriconazole (VCZ) were 636, 160, 35 μg/L, respectively, calculated based on S/N=3 at the injection volume of 1 μL. It is applicable to the field, high-throughput and highly sensitive detection of antibiotics.

In this study, cold cathode electron sources using deep-UV photons to excite gold cathode and microchannel plate (MCP) were employed to configure a high-quality electron impact ion source (EI) in a mass spectrometry. As an electron multiplying device, MCP can amplify weak signal by thousands of times. Gold was used as a photocathode and it had the characteristics of simple excitation, stable photoemission, and uniform photocurrent density distribution. Combining the characteristics of the two, a series of research were carried out. The gold cathode JGS2 was formed by evaporation gold film on JGS2 quartz glass, and the gold-cathode MCP was formed by evaporation gold film on the input surface of MCP, respectively. The two were assembled in different combinations to develop two kinds of cold cathode electronic sources. Firstly, the deep-UV excited gold cathode MCP was used as the electron source, the output electron beam current range was 10-11-10-6 A. When the excitation light source was stable, the electron source could reach a stable state quickly and maintain a stable output for a long time (>5 h). Under the interaction of gold cathode MCP and gold cathode JGS2, the maximum output electron beam current of electron source could reach 10-5 A. At the same time, the contributions of reflected photoelectrons and transmitted photoelectrons generated by the gold cathode to the output current under different electric fields were discussed, as for the deeper working mechanism to be solved. In addition, the output electron beam current could be continuously adjusted by changing the working voltage of MCP, so that the cold cathode electron source could be flexibly and quickly adjusted and responded within a certain range. Finally, a fluorescent screen was used to observe the imaging quality of the output current generated by the above system, and the RGB image captured by the high-definition camera was converted into a grayscale image, and the non-uniformity of the image was calculated to be about 6.5%. Therefore, the imaging uniformity of the cold cathode electron source developed in this paper on the phosphor screen was good. The above results showed that the cold cathode electron source composed of gold cathode MCP excited or combined with gold cathode JGS2 by deep ultraviolet light had the characteristics of long working stability, good uniformity, wide and continuously adjustable beam current range. It can realize the functions of photoelectric conversion and electron multiplication, and is expected to provide a new alternative for the development of electron sources in EI sources in the future.

The multi-component pharmacokinetic of traditional Chinese medicine (TCM) is vital to clarify the theory and mechanism of TCM. Based on information of absorption, distribution, metabolism, and excretion dynamic changes for active components of TCM in vivo, the material basis for the safety and efficacy can be elucidated via combination with pharmacodynamics. However, due to the complexity and diversity of TCM components, and their complicated and unclear interactions with biological system, there are many bottleneck problems for the multi-component pharmacokinetics of TCM, such as the numerous chemical composition and diverse metabolic reaction make it difficult to identify their structures and interpret metabolic pathway in vivo; and unclear active components, low concentrations of target components in biological samples, endogenous interferences from matrix and lack of authentic standards bring difficulties to establish qualitative and quantitative methods. In recent years, the pretreatment methods for biological samples have been well developed. The separation and extraction efficiency for multi-component of TCM in vivo and in vitro have been significantly improved using various high-throughput, fast and automated pretreatment techniques. The development of chromatography and mass spectrometry promotes the rapid comprehensive and accurate discovery and quantification for multi-component of TCM. Novel analytical methods such as mass spectrometry imaging was used to provide new strategies for multi-component pharmacokinetics of TCM. In this paper, the development and application of analytical techniques for multi-component pharmacokinetic of TCM in the past 10 years were summarized, and a brief perspective was discussed. Firstly, the pretreatment of biological sample was introduced, the advantages and disadvantages of some usual sample pretreatment methods were compared such as protein precipitation and liquid-liquid extraction, solid phase extraction, microextraction, microdialysis. The applications of these different pretreatment techniques in the pharmacokinetics research of TCM were interviewed. Then, the principles and developments of different chromatographic techniques including high performance liquid chromatography and gas chromatography used in multi-component pharmacokinetic of TCM were introduced. Finally, the mass spectrometry ionization techniques were summarized and discussed including electrospray ionization and atmospheric pressure chemical ionization for liquid chromatography, electron impact and chemical ionization for gas chromatography, desorption electrospray ionization, direct analysis in real time, mass spectrometry imaging.

The ancient porcelain is the treasure of Chinese civilization. In this paper, multiple surface analysis tools were applied to characterize the attractive silvery bright spots on the glaze of black-glazed tea bowl fragment. The raindrop-shaped silver flecks covering the surface were symbols of North China oil spots. High-resolution time of flight-secondary ion mass spectrometry (TOF-SIMS) data confirmed the main component of the oil spot was iron oxide. Positive ions were Fe+ (m/z 55.93), FeO+ (m/z 71.93), Fe2O+ (m/z 127.86), and negative ions were FeO- (m/z 71.93), FeO-2 (m/z 87.92). A series of peaks were detected by micro-Raman spectroscopy, such as 230, 294, 412, 502, 611, 1 337 cm-1. This suggested existence of hematite (α-Fe2O3) in the spot. Secondary ion imaging of TOF-SIMS indicated the oil spots (~120 μm) was formed by self-organization and dispersion of hundreds hexagonal hematite crystal (~2-10 μm). Hematite was spatially complementary to alkaline calcareous glaze that contains silicon, aluminum, calcium, and sodium. TOF-SIMS depth profiling of the spot suggested a more than 5 μm continuous hematite layer on the glaze of black-glazed tea bowl. The main mineral of α-Fe2O3 crystals was hematite, which was ochre usually. Specular hematite, a subspecies of hematite with silver or black color, was believed to play critical role in the formation of the oil spot. With the optical microscope observations, we believed that the silvery material on the surface of the oil spots should be a thin layer of specular hematite and the lower ochre layer was hematite. In fact, the oil spot appeared silvery-white and reflective when viewed from 15° to 165°, while it appeared ochre when the angles of gaze was not greater than 15° from the glazed surface of the specimen. The extraordinary visual property of color changing with different angle of gaze formed the charm of Song dynasty oil spot tea bowls. With these results, a hypothesis for the formation of the North China oil spots was enlightened. The molten phase of Fe-rich soy-black glaze gradually formed micron-sized hematite particulates at sealed kiln of high temperature (1 250 ℃). When the kiln was unsealed, the hot porcelain was exposed to cold air immediately. A thin layer of specular hematite was generated on top of hematite particulates.

In the past decades, systematic isolation and structural identification of chemical components from plant material, especially traditional Chinese medicine, have provided a large number of chemical drugs and lead structures for clinic. However, there are still a large number of trace components in traditional Chinese medicine with novel chemical structures and specific pharmacological activities, which need to be further analyzed. With the development of modern analytical technology, the network technology based on tandem mass spectrometry and cluster analysis shows many advantages in trace analysis of complex components. In this paper, a method of high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF MS) was developed for the analysis of the main chemical constituents in the root bark of Lycium barbarum L. The aqueous extract sample was separated by methanol aqueous through C18-solid phase extraction, and then the 50% methanol aqueous elution was analyzed using HPLC-Q-TOF MS with C18 column. The ions were monitored in both positive mode and negative mode of ESI with the scanning ranges of m/z 100-300 and 300-2 000. The trace chemical components were analyzed by molecular network technology. The MS data files were converted to the mzXML format and the molecular network was generated on GNPS, then visualized with Cytoscape, and the structures of compounds were predicted based on literature data. Twenty one known compounds in Cortex Lycii were verified by manual analysis technique and eleven new components were firstly identified by molecular networking. It is worth reporting that compound 24 and 25 are different from cyclooctapeptides previously found in the root bark of Lycium chinense (another source of Cortex Lycii), indicating that they can be used as markers for the identification of two species of Cortex Lycii. This work lays a research foundation for promoting the effective application of Lycium barbarum L. root bark.

Recently, different types of ion mobility techniques have sprung up. Combined with mass spectrometry, the utility of ion mobility spectrometry has been enhanced in metabolomics, natural products, characterization of supramolecular materials, and other research fields. Since small molecule metabolites provide deep insight into the dynamic phenotypes of biological systems and show potential value in disease diagnosis and functional interpretation, in-depth analysis of small molecule metabolites plays a key role in medicine and pharmacy. The potential benefits of ion mobility spectrometry used in chiral recognition of amino acids, structural analysis of glycans, and structural characterization of lipids and steroids have become the specific focus of work. However, small molecule metabolites possess a wide variety of chemical properties, ubiquitous isomerism, and various biological functions, so it is difficult to analyze small molecule metabolites comprehensively. On the other hand, small molecule metabolites with low concentrations usually exist in various complex biological matrices, such as plasma, feces, urine, saliva, sweat, infected tissues or exudates, breath, and breast milk, which pose additional challenges to researchers. Over the last few decades, ion mobility-mass spectrometry (IM-MS) has undergone inordinate growth in instrument development and performance, which has opened a new door to rapidly analyze small molecular metabolites in complex biological matrices. Small molecular metabolites and their isomers can be distinguished and characterized in milliseconds by IM-MS that offer high selectivity and three-dimensional information about them, including mass-charge ratio, collision cross section (CCS), and structural information. The collision cross section can be used as an additional identification basis in targeted and untargeted analyses. In this paper, the main commercial IM-MS instruments were briefly covered. An overview of the latest applications in small molecular metabolites was offered. Additionally, the advantages and shortcomings of IM-MS in the analysis of small molecular metabolites were discussed. And the future application of particular and unknown metabolites by IM-MS in the studies on the biological mechanism and precision medicine was prospected.

With the rapid development of modern detection technology and scientific research, the chemical structures and functions of isomers are constantly being revealed. The isomer molecules may have completely different biochemical activities, and a certain molecule of the isomer may play an important role in disease pathogenesis or disease treatment, while the other is the opposite. Therefore, the separation and identification of isomers and the exploration of their structures are helpful to furtherly understand the operating mechanism of life, and become one of the research hotspots in the field of analytical chemistry and life sciences. Ion mobility spectrometry (IMS), which has developed rapidly in recent years, is an instrument technology that can analyze the spatial structure of molecules. It can distinguish the isomerism of a certain molecule by measuring the difference in the collision cross-section between different molecular ions and airflow in the gas phase. IMS coupled with mass spectrometry (IMS-MS) is a powerful separation and analysis technology that adds a mobility separation dimension for MS to improve ion structure separation and determination, while also enhances ion mass selection in mobility technology and makes the separation of the analyte have high selectivity. IMS-MS technology has been highly concerned and widely used in the fields of small molecule/metabolite identification, proteomics research, host-guest complexes, and molecular structure identification. This paper was focused on the working principle of different types of IMS, the latest application in different types of isomers and the prospect of IMS-MS.

Combined with mass spectrometry, ion spectroscopy can obtain a spectrum of the target ion by measuring its intensity change, which is induced by laser strength and wavelength. It integrates the high sensitivity of mass spectrometry and the structural specificity of spectroscopy, and thus proves to be very useful in structure characterization of complex biomolecules, such as proteins, peptides, glycans, oligonucleotides, etc. However, the electronic or vibrational spectra becomes too complex to be resolved when analyzing isomeric ions. Ion mobility spectrometry (IMS) allows ionized molecules to be separated on the basis of mobilities in the gas phase, and its coupling with electrospray and MALDI ion sources opens up possibilities for structural studies of a wide range of biomolecules in gas-phase. Ion mobility spectrometry coupled with mass spectrometry has seen spectacular growth for the last two decades. The introduction of ion mobility to ion spectroscopy has been of growing attention in recent years. While IMS can be used as an isomer filter to reduce spectral congestion of ions, highly resolved ion spectra facilitates the identification of the isomer peaks separated by IMS. Taken together, spectra and collision cross section (CCS) measurements on the same system prove to be rather useful for structural analysis and provide clearer spectroscopic fingerprint to isomers. Therefore, this paper briefly summarized advances in ion spectroscopy research based on ion mobility-mass spectrometry technology, introduced representative researches, and prospected possible development in multi-dimensional structural mass spectrometry.

The commonly used analytical techniques for the detection of primary aromatic amines (PAAs) in food contact materials (FCMs) include gas chromatography-mass spectrometry (GC-MS), capillary electrophoresis (CE), high-performance liquid chromatography (HPLC), HPLC-tandem mass spectrometry (HPLC-MS/MS), HPLC-high resolution mass spectrometry (HPLC-HRMS), etc. The migration of PAAs was determined in various types of FCMs using the above-mentioned techniques, such as laminated flexible packaging materials, polyamide cookware, plastic bags, and napkins. For the migration experiment, those methods generally adopted a single contact time and contact temperature, which may deviate from the migration amount occurred in the actualapplication. In contrast, European Union Directive (EU) No 10/2011 (annex Ⅲ) specified the time/temperature conditions for migration test of food simulants and plastics. Therefore, it is reliable to detect the migration of PAAs based on the expected food contact situations including food nature, contact time, and contact temperature for different types of FCMs. In this study, a method of high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for the determination of the migration of 33 PAAs from FCMs and articles. 20% ethanol, 50% ethanol and 3% acetic acid solutions were used as food simulant solutions to simulate the hydrophilic, lipophilic and acidic food. For FCMs, such as disposable paper cups, colored plastic knives and forks, food bags, plastic milk bottles, pacifiers, etc., they were cut into rectangles with the side lengths of 0.5-1.0 cm. FCM samples of 5 g were weighed in a volumetric flask, and food simulant immersion solution of 100 mL was added. According to the physiochemical properties of the main ingredients in food and whether the FCMs and articles are expected to repeat contact with food, the conditions of food simulant solution and migration experiments were optimized. Chromatographic separation of the migration solution was performed on a Kinetex F5 column by a gradient elution of 0.05% formic acid-methanol solution. The detection was completed in positive electrospray ionization (ESI+) and scheduled multiple reaction monitoring (MRM) mode. The external standard method was used for quantitation. The absolute matrix effects (AMEs) of the 33 PAAs in the migration solution of 20% ethanol, 50% ethanol, and 3% acetic acid (pH 7.0) were 86.1%-97.3%, 88.7%-104.0%, and 62.7%-81.3%, respectively. Good linearity (r>0.99) was obtained within their respective linear ranges. The limits of detection (LODs) and quantitation (LOQs) were 0.02-1.04 μg/kg and 0.07-3.26 μg/kg, respectively. This method is sensitive, reliable, and suitable for the accurate determination of the migration of PAAs from FCMs and articles.

To investigate the effect of substitution sites of the nitro group on the UV photodissociation (UVPD) of nitrobenzimidazole isomers, UVPD mass spectra and spectra of protonated ions of 2-nitrobenzimidazole （2-NBI）, 5-nitrobenzimidazole (5-NBI) and 7-nitrobenzimidazole (7-NBI) were studied by a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer combined with a tunable UV laser. Experimental results showed that the method of UVPD can distinguish the three isomers effectively. Although the UVPD spectrum of 2-NBI extended to about 360 nm, the UVPD spectra of 5-NBI and 7-NBI ended at 290 and 300 nm, respectively. As to UVPD mass spectra, the dissociation products were more diverse than the ones observed in CID experiments. And the yields of some ions significantly depended on the wavelength applied. Combined with theoretical calculations, the most important dissociation channels for the three ions were investigated in detail. For 2-NBI, two fragment ions of m/z 147 and 146 were observed, which were formed by the loss of OH• and H2O resulting from one and two H atom transfers on the N atom of imidazole ring, respectively. For 5-NBI, the process of H transfer couldn’t happen due to the long distance between the nitro group and the imidazole ring. Therefore, only fragment ions of m/z 148 by the loss of O atom were observed. For 7-NBI, its nitro group located between the benzene ring and the imidazole ring, thus only one H atom could be transferred. Therefore, only the m/z 147 (OH• loss) fragment ions could be formed in the process. The channels for the generation of fragment ions of m/z 134 and 106 were also analyzed and discussed in this paper.

The selective C—C bond activation is a frontier research topic and of great significance in the field of chemistry, especially for biosciences. Due to the existence of many C—C bonds with similar activities in compounds, it is difficult to selectively activate one of the C—C bonds. In this paper, the newly synthesized peptide derivatives composed of unnatural amino acids were used as a subject to demonstrate how radical-mediated selective C—C bond activation and isomer differentiation work. TEMPO radical initiator was employed to introduce o-methylbenzoyl (Bz) radical into the peptide derivatives, and successfully prepared ［Bz-M+H］•+ radical ions in the gas phase. Through tandem mass spectrometry experiments, it had been found that ［Bz-M+H］•+ showed higher reactivity than the protonated peptide molecule ［M+H］+, giving a more diversified gas-phase dissociation reactions. The main fragmentation of ［M+H］+ was the cleavage of amide bond to give rise to ［y1+2H］+ (m/z 160.134 0, RA 100%), a1+ (m/z 86.097 2, RA 74%), and ［(M+H)-HCOOEt］+ (m/z 199.181 5, RA 52%). In contrast, the fragment ions of ［Bz-M+H］•+ included ［Bz•-a1］+ (m/z 202.97), ［Bz•-b1］+ (m/z 231.03), ［Bz•-c1+H］+ (m/z 133.95) and ［(Bz-M+H)-HCOOEt］+ (m/z 316.18, RA 100%). N-terminal fragments of ［Bz-M+H］•+ were observed with the radical part •CH2C6H4CO still attached to the fragmentation. To distinguish these ions from the normal fragments, the prefix Bz• was introduced, such as, ［Bz•-a1］+. More interestingly, ［(Bz-M+H)-HCOOEt］+ was the base peak of ［Bz-M+H］•+, which was produced by breaking the Cα—C adjacent to the ester group of peptide derivative. In contrast, the relative abundance of ［(M+H)-HCOOEt］+ from ［M+H］+ was only 50%. The formation mechanism of ［(M+H)-HCOOEt］+ had been experimentally confirmed to be completed by the two-step reaction of losing EtOH and CO successively. For isomers B1 and B2, their CID spectra of ［Bz-M+H］•+ had high similarity, but the abundance of fragment ion ［Bz•-a1］+ was obviously different (m/z 203, RA 40% for B1, RA 60% for B2). The fragment ions ［Bz•-a1］+ and ［(Bz-M+H)-HCOOEt］+ of ［Bz-M+H］•+ can be used as sensitive probes for isomer discrimination and selective C—C bond cleavage. The research provides new strategy to distinguish peptide isomers and to cleavage selective C—C bond with radical participation in mass spectrometer.

Glow discharge ionization source can be used to analyze solid sample, liquid sample and gas sample. At present, glow discharge optical emission spectrometer (GD-OES) and glow discharge mass spectrometer (GD-MS) are mainly used to the elemental analysis of inorganic solid samples and quantitative depth profile analysis, including direct current (DC) power supply and radio frequency (RF) power supply. In this paper, the ionization of liquid sample and gas sample by low frequency radio frequency glow discharge (Lf-RFGD) was researched, and the glow discharge structure constructed was connected to timeof flight mass spectrometer(TOF MS). The influences of the vacuum degree of ionization chamber, the size of sample inlet capillary, the auxiliary gas pressure, the discharge radio frequency and the voltage difference between electrode plates on the ionization efficiency were studied. The optimal analysis conditions are the vacuum degree of ionization chamber is about 30 Pa, the length of sample inlet capillary is 150 mm and the inner diameter is 0.25 mm, the auxiliary gas pressure is about1.0 MPa, the low discharge frequency is 2 MHz, the voltage difference between electrode plates is about 100 V. Under these conditions, the discharge power is about 20 W,the detection limit of liquid sample is 0.1 pg and volatile sample is 20 mg/m3, and the detection resolution (full width at half maximum, FWHM) is about 3 000. Combined with samples testing, the Lf-RFGD TOF MS was preliminarily applied to the drug solution and volatile organic compounds (VOCs). However, the sensitivity of this instrument for detecting non volatile liquid sample was not good compared with the conventional detection instrument. The reason is that high proton affinity and low ionization potential are needed to obtain good detection sensitivity in the positive ion mode of mass spectrometer, and non volatile liquid sample without pretreatment is not easy to meet the condition of high proton affinity under low power glow discharge condition. Successfully, a lowcost, portable approach based on the application of atmospheric sampling Lf-RFGD TOF MS has been developed for near real time measurement of trace VOCs. In this context, the glow discharge excitation source offers attractive alternative for development of low cost VOCs and elemental analysis instrument. Lf-RFGD as an excitation source has unique advantages with respect to development of hand held instrument such as low cost, low power consumption, and analytical versatility.

Stable isotope ratios of carbon, nitrogen, hydrogen and oxygen act as “nature’s recorder”. As a carrier for individual human information, human hair can be measured by isotope ratio mass spectrometry (IRMS) to translate into information about people’s dietary habits, health condition and life track. The basic principle behind establishing dietary lifestyle using isotopic profiles of human hair is the fact that the body’s only source of C, N is a person’s staple diet. It may have significant differences in carbon, nitrogen isotopic compositions of human hair that are living at different regions. The aim of the study was to analyze the discrepancy of 15N and 13C stable isotope ratios in human hair collected from different cities, and explore the relationship between carbon and nitrogen isotope ratios and human groups, such as gender and age. The carbon and nitrogen isotope ratios in the human hair of 247 local residents from 8 different cities were investigated by IRMS. The results showed that there were significant difference in carbon and nitrogen stable isotope ratios of human hair from different cities. The value of δ13C was negatively correlated with vegetable consumption per capita. The value of δ15N was positively correlated with meat consumption per capita, and might be increased by high intake of fish. The relationship between δ13C, δ15N and the factors of gender and age demonstrated that there were no significant difference between males and females, but the age of females showed a weakly negative correlation with δ13C. By comparing the data of this paper and other literatures, the carbon and nitrogen stable isotopes in the hair of residents in China were different from other countries, which implied that there were various dietary habits in different countries.

This paper identifies shengma fiber by burning method, estimating method by microscope, coloring with medical drugs, dissolution method and infrared radiation spectrum method, and compared with the identification method of viscose and ramie fiber. The results show that shengma fiber possesses a number of longitudinal deep trenches. It is unique that the cross-section is plum-shaped, and has a clear skin-core layer structure. Irregularly, the edge of it possesses a deeply embossed concave convex structure. Besides, iodine-potassium iodide solution staining of shengma fiber turns out to be blue-green. And under normal temperature, the sulfuric acid solution (the concentration is 40%) has partial dissolution; the hydrochloric acid solution (the concentration is 36%~38%) is thick and has some light yellow solution. The St. Ma Infrared absorption spectra of shengma fiber is similar to viscose fiber. However in 1210~1000 cm^(-1) fingerprint area it is quite different from ramie fiber. [ABSTRACT FROM AUTHOR]

Advance into laboratory to approach chemical experiment as early as possible for chemical undergraduate can guide and inspire their professional interest. It also improves students' learning initiative, and is beneficial to cultivate students' innovation consciousness and innovation ability. Through the reform of experimental teaching, more students are encouraged to participate in the innovation of advance into the laboratory, the reform can not only improve the practical ability, but also deepen the understanding of theoretical knowledge to enhance the students' comprehensive ability greatly. This paper is centered on its effectiveness as following aspects: promoting the students' theory of learning,improving students' experimental skills, mining scientific research ability of students, cultivating comprehensive quality of undergraduate, and so on. [ABSTRACT FROM AUTHOR]

This paper studies two-step synthetic process of TEX (4,10-dinitro-2,6, 8,12-tetraoxa-4, 10-diazatetracyclo-[5. 5. 0. 05,9 03,11]-dodecane) and the effects of key factors on the yield of DFTHP (intermediate) and TEX. The results show that the yield of DFTHP could reach to 68. 3% when the adjusted pH value of reaction solution reaches to 9 by saturated NaOH solution. When the volume ratio of fuming HNO3 to concentrated H2SO4 is 3 : 2, and the ratio of nitrating agent (mL) to DFTHP(g) is 3 : 1, the yield of TEX raises to 59. 7% . The optimized overall yield of TEX obtained from two-step synthetic process could be 40. 8%. [ABSTRACT FROM AUTHOR]