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Sucrose esters (SEs) are crucial tobacco smoke flavor precursors and play a significant role in tobacco's functionality. Due to their structural complexity, the separation and analysis of SEs in tobacco remain a major challenge, and massive structures of SEs have not yet been fully identified. In this study, the fractions enriched in SEs were obtained from oriental and flue‐cured tobacco through a series of pretreatments, and two types of SEs (Types I and II) were distinguished by liquid chromatography‐tandem mass spectrometry (LC‐MSn) analysis, with Type II SEs newly characterized in tobacco. Five groups of main SEs were further purified using preparative high‐performance LC (HPLC) coupled to an evaporative light scattering detector, and their structures were characterized by nuclear magnetic resonance spectrometry techniques including 1H, 13C, correlation spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple bond correlation. By combining LC‐MSn and nuclear magnetic resonance spectrometry, the structures of eight SE isomers were finally proposed, of which four were newly identified. These findings further enhance the understanding of the structural diversity of SEs in tobacco, serving as a valuable reference for future research on the elucidation, synthesis, and metabolism of SEs. [ABSTRACT FROM AUTHOR]

Tobacco has a high economic value as the largest cash crop worldwide. The quality of flue-cured tobacco is closely related to the overall status of compounds in fresh tobacco leaves, and the aroma precursor plays a key role in the aroma quality of flue-cured tobacco. The untargeted metabolomics and label-free quantitative proteomics analysis of tobacco leaves in three growth stages (root stretching, prosperous growth, and maturation) retrieved 243 metabolites and 4313 proteins (944 differentially expressed proteins), which showed that carbohydrate, amino acid, and fatty acid metabolism varies among the three growth stages. Also, the most of amino acids, organic acids, fatty acids, and polyphenols reduced in the vegetative growth stage, while increased in the reproductive growth stage. On the other hand, alkaloids such as nicotine, nornicotine, and anatabine increased continuously in tobacco leaves during the three growth stages. This study helps us understand the growth and development characteristics of Yun87 flue-cured tobacco in the field before harvest, and it provides a certain omics basis for the industrial crop flue-cured tobacco. • The metabolomic combined with proteomic was used in the aroma precursors study. • The tobacco leaves' aroma precursors synthesis significantly changes during growth. • The levels of amino acids were higher in RP group than other groups. • The contents of alkaloids continuously increased during the three growth stages. [ABSTRACT FROM AUTHOR]

Mass spectrometric analysis of non-volatile salts containing samples remains challenging due to salt-induced ion suppression and contamination. This challenge is even more pronounced for a liquid chromatography-mass spectrometry analysis, where the accumulation of salts in the transmission system poses an ongoing problem. In this study, a novel thermal assisted recrystallization ionization mass spectrometry (TARI-MS) device was developed to achieve efficient on-line desalting and prolonged analysis of saline samples. The core component of this device was a heated plate positioned between the electrospray unit and the MS inlet. The desalting mechanism was demonstrated as the spontaneous separation of target molecules from salts during the "crystallization" process. After optimization, the angle between the nebulizer and the heated plate was 45°; the distance between the front end of the heated plate and the MS inlet was 2 mm; the distance between the front edge of the heated plate and the center of the sample spray projected onto the heating plate was 3 mm; the distance between the emitter of nebulizer and the heated plate was 3 mm. TARI-MS realized direct analysis of eight drugs dissolved in eight commonly used non-volatile salts solutions (up to 0.5 mol/L). The high sensitivity, repeatability, linearity, accuracy, and intra- and inter-day precision of TARI-MS confirm its reliability as a robust tool for the analysis of saline samples. Furthermore, TARI-MS allowed continuous analysis of salty eluates of LC for up to nearly 1 h without maintenance and verified the feasibility of LC-MS analysis through detecting a five-drug mixture and a crude aripiprazole product. Finally, six impurities in the crude aripiprazole product were successfully detected by LC-TARI-MS. The established method holds promise for applications across academic and pharmaceutical domains. [Display omitted] • A novel on-line desalting ionization device has been designed, constructed and applied. • Superior desalting performance and salt tolerance has been verified. • Detection of eight drugs dissolved in eight commonly used non-volatile salts/buffers has been realized. • Feasibility of LC-MS analysis of crude drug or mixtures has been demonstrated. [ABSTRACT FROM AUTHOR]

Phenyloxenium ion (POI) is an important intermediate in organic reactions, however, its generation and reactivity have not been extensively investigated. In this study, POI is produced in the gas phase by electrospray ionization tandem mass spectrometry (ESI-MS/MS), isolated for gas phase ion-molecule reactions, and used theoretical calculations to reveal mechanisms to those reactions. It forms adduct ions with H 2 O, methanol, ethanol, benzene, and toluene, although the structures of the adduct ions are not well-resolved. In contrast, ortho -cyclization with nitriles has been verified by the reaction with acetonitrile and theoretical calculation. Further, Hydride transfer reaction during the reaction with tetrahydrofuran in the gas phase led to experimental values of the hydride affinity and electronic state of POI. Electron transfer studies revealed that the ionization potential of phenoxy radical locates in the range of 8.01–9.19 eV, in line with the calculated value of 8.60 eV for the singlet state POI. Phenyloxenium ion (POI) is a very important organic reaction intermediate, however, seldom has been studied in the gas-phase. A combined reaction mass spectrometry and theoretical calculations research on key reaction patterns, such as, chemical addition, ortho -cyclization, hydride transfer, and electron transfer towards selected organic reagents reveals characteristic reactivity of POI. [Display omitted] [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are considered one of the significant contributors to air pollution because they are toxic, difficult to remove, come from a wide range of sources, and can easily cause damage to the environment and human health. There is an urgent need for effective means to reduce their emissions. The current treatment technologies for VOCs include catalytic oxidation, adsorption, condensation, and recovery. Catalytic oxidation technology stands out among the others thanks to its high catalytic efficiency, low energy requirement, and lack of secondary pollution. The difficulty of this technology lies in the development of efficient catalysts. The research on loaded noble metal catalysts and non-noble metal oxide catalysts in this area over the past few years is briefly described in this work. Firstly, the catalytic destruction mechanism of organic volatile compounds is introduced. Secondly, the effects of structural modulation during catalytic oxidation, such as the adjustment of noble metal particle size and morphology, metal doping, and defect engineering, on the conformational relationships are discussed. Finally, the challenges faced by thermal catalytic oxidation for the degradation of VOCs are discussed, and the prospects for its development are presented. [ABSTRACT FROM AUTHOR]

Pre-processing of near-infrared (NIR) spectral data has become a necessary part of chemometrics modeling and is widely used in many practical applications. The objective of the pre-processing is to remove physical phenomena in the spectra in order to improve subsequent qualitative or quantitative analysis. Herein, a localized version of standard normal variate (SNV) is proposed, in which the correction parameters are estimated from local spectral areas. The method of determining the optimal spectral segmentation is also presented. Compared with full range methods, the local method demonstrates advantages in spectral linearity correction, model interpretation and prediction accuracy. Several benchmark NIR data sets were studied in our experiments; the proposed method achieved comparable performance against proven full range methods, with the reduction of prediction errors being statistically significant in many cases. [ABSTRACT FROM AUTHOR]

Abstract: “Metabonomics” method requires the development of rapid, advanced analytical tools and GC will play an important role for its special advantage. In this study we show the application of GC-based metabonomics to investigate the control and type 2 diabetes (DM2) patients by urinary organic acids metabolic profile. After peak matching, multivariate statistical analysis methods: principal components analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were used. The results showed that there was a relationship between organic acids metabolic profiles and DM2, and PLS-DA can distinguish the DM2 patients from the control. Five organic acids as potential biomarkers were identified. [Copyright &y& Elsevier]

Abstract: The major components of the plant curcuma longa are the curcuminoids that include curcumin, demethoxycurcumin and bisdemethoxycurcumin. It has been reported the curcuminoids have some important activities. A new CZE method with diode array detection has been developed for the separation and determination of the curcumin, demethoxycurcumin and bisdemethoxycurcumin. Three curcuminoids could be readily separated within 7min with a 15mM sodium tetraborate buffer containing 10% methanol (v/v) at pH 10.8, 25kV and 30°C. The method has been validated and shows good performance with respect to selectivity, reproducibility, linearity, limits of detection and recovery. The proposed method was successfully applied to determine the curcuminoids in urine. [Copyright &y& Elsevier]

After dilution centrifugation, enrichment culture, and gradient plate screening, a series of strains that can adapt to concentrated tobacco waste water extract (TWE) and exhibit metabolic activity were isolated from concentrated TWE during the paper-making reconstituted tobacco process. Their morphological, physiological and biochemical characteristics were identified. The isolated strains were added into concentrated TWE for fermentation. The growth and metabolism characteristics and their effects on the composition of metabolites in TWE were investigated. The results showed that a yeast strain MC-9A1 resistant to high stress was isolated from concentrated TWE, which belonged to the species Zygosaccharomyces bailii. The strain MC-9A1 could grow in concentrated TWE and carried out normal metabolic activities, consuming a lot of sugar. At the same time, MC-9A1 consumed a large number of strongly polar substances and a small number of moderately polar substances in concentrated TWE, and generated a large number of weakly polar or non-polar substances. More than 310 metabolites were significantly up-regulated or down-regulated. For example, acetamide and xylitol increased significantly, while arbutin and D-galacturonic acid decreased significantly. The sensory evaluation results showed that the sensory effect was improved by fermentation of MC-9A1 in concentrated TWE, which increased aroma quality, while decreased odor and the residual. [ABSTRACT FROM AUTHOR]

Abstract: A simple, rapid and low-cost method using capillary electrophoresis coupled with field-amplified sample stacking and electrochemical detection was developed for the separation and determination of monoamines. In this present work, a systematic study of the parameters (pH value and concentration of electrophoretic buffer, composition of sample solvent, injection voltage and time) affecting separation and on-line concentration of monoamines has been performed enabling the detection sensitivity of these monoamines to be improved by 5000 times compared with the conventional electrokinetic injection. This developed method was applied to the direct analysis of these monoamines in human urine without off-line sample preconcentration. Due to the requirement for urine dilution to minimize the detrimental effects of high salt on analyte stacking, the real sensitivity improvement is about 50-fold when applying the optimized method to urine samples. In order to quantitate these monoamines accurately, internal standard calibration curves were constructed with standard monoamines in presence of salt with similar concentration as in human urine. In the method validation, the calibration curves were linear over a range of 1.0×10−9 to 2.5×10−8 mol/L for each monoamine and the limits of detection (signal to noise ratio of 3) for these monoamines were in the sub-nmol/L concentration range (6.0×10−10 mol/L). [Copyright &y& Elsevier]

Influence of substitutional Fe, Al and Mg atoms on the corrosion of α-U(110) surface was studied by DFT + U method. The calculations results indicate that impurity atoms inhibit the dissociation of H2O molecular. Although the impurity atoms do not impede the dissociation of O2 molecular, they lower the binding energy of the dissociated O atoms with the substitutional surfaces. Through the investigation on the surface diffusion and into-bulk penetration, it could be confirmed that Fe, Al and Mg atoms accelerate the hydrogenation of α-uranium surface, while improve the anti-oxidizing ability of α-uranium. [ABSTRACT FROM AUTHOR]

A novel infrared-assisted extraction coupled to headspace solid-phase microextraction followed by gas chromatography with mass spectrometry method has been developed for the rapid determination of the volatile components in tobacco. The optimal extraction conditions for maximizing the extraction efficiency were as follows: 65 μm polydimethylsiloxane-divinylbenzene fiber, extraction time of 20 min, infrared power of 175 W, and distance between the infrared lamp and the headspace vial of 2 cm. Under the optimum conditions, 50 components were found to exist in all ten tobacco samples from different geographical origins. Compared with conventional water-bath heating and nonheating extraction methods, the extraction efficiency of infrared-assisted extraction was greatly improved. Furthermore, multivariate analysis including principal component analysis, hierarchical cluster analysis, and similarity analysis were performed to evaluate the chemical information of these samples and divided them into three classifications, including rich, moderate, and fresh flavors. The above-mentioned classification results were consistent with the sensory evaluation, which was pivotal and meaningful for tobacco discrimination. As a simple, fast, cost-effective, and highly efficient method, the infrared-assisted extraction coupled to headspace solid-phase microextraction technique is powerful and promising for distinguishing the geographical origins of the tobacco samples coupled to suitable chemometrics. [ABSTRACT FROM AUTHOR]

An ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction was first employed to determine the volatile components in tobacco samples. The method combined the advantages of ultrasound, microwave, and headspace solid-phase microextraction. The extraction, separation, and enrichment were performed in a single step, which could greatly simplify the operation and reduce the whole pretreatment time. In the developed method, several experimental parameters, such as fiber type, ultrasound power, and irradiation time, were optimized to improve sampling efficiency. Under the optimal conditions, there were 37, 36, 34, and 36 components identified in tobacco from Guizhou, Hunan, Yunnan, and Zimbabwe, respectively, including esters, heterocycles, alkanes, ketones, terpenoids, acids, phenols, and alcohols. The compound types were roughly the same while the contents were varied from different origins due to the disparity of their growing conditions, such as soil, water, and climate. In addition, the ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction method was compared with the microwave-assisted extraction coupled to headspace solid-phase microextraction and headspace solid-phase microextraction methods. More types of volatile components were obtained by using the ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction method, moreover, the contents were high. The results indicated that the ultrasound-microwave synergistic extraction coupled to headspace solid-phase microextraction technique was a simple, time-saving and highly efficient approach, which was especially suitable for analysis of the volatile components in tobacco. [ABSTRACT FROM AUTHOR]

Abstract: The cryIAc and sck genes were introduced to the rice for the purpose of improving the insect resistance. Metabolic profiles of wild and transgenic rice were compared to assess the unintended effects related to gene modification. Wild samples with different sowing dates or sites were also examined to determine the environmental effects on metabolites. The polar compounds of grains were extracted, trimethylsilylated and analyzed by gas chromatography-flame ionization detection (GC-FID). Partial least squares-discriminant analysis (PLS-DA) and principal component analysis (PCA) were applied to differentiate transgenic and wild rice grains. The significantly distinguishable metabolites were picked out, and then identified by gas chromatography–mass spectrometry (GC–MS). It was found that both the environment and gene manipulation had remarkable impacts on the contents of glycerol-3-phosphate, citric acid, linoleic acid, oleic acid, hexadecanoic acid, 2,3-dihydroxypropyl ester, sucrose, 9-octadecenoic acid (Z)-, 2,3-dihydroxypropyl ester and so on. Sucrose, mannitol and glutamic acid had a significant increase in transgenic grains in contrast to those in non-genetically modified (GM) rice. [Copyright &y& Elsevier]

Abstract: Two mutants of E. coli with deletion of sdhAB and ackA-pta genes respectively and their wild-type strains were subjected to gas chromatography-flame-ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC–MS) metabolomics analysis. Intracellular metabolites of the three strains were profiled by GC-FID firstly. Methodological evaluation of the employed platform indicated that the limit of detection ranges were from 0.2 to 12.5ng for some representative metabolites and the corresponding recoveries were varied from 68.7 to 122.7%. Secondly, multivariable data analysis was applied to the acquired data sets. As expected, the three phenotypes could be easily differentiated, and the perturbed metabolite pools in the genetically modified strains were screened. Lastly, the metabolites playing key roles in the differentiation were further identified by GC–MS. It was confirmed that succinic acid and aspartic acid were similarly affected in the modified strains. But proline content was altered contrarily. Additionally, deletion of sdhAB gene also affected the growth property of relevant mutant greatly. The potential mechanism was postulated accordingly. [Copyright &y& Elsevier]

Abstract: Metabolomics is a new branch of systems biology exerting its influence in many aspects. In order to appraise the effects of antibiotics on central carbon metabolism, a CE based method was set up. With this platform, we estimated the organic acid metabolite pools’ fluctuation of Escherichia coli and Pseudomonas aeruginosa cultured under 11 different antibiotics’ stimuli. Multivariate data analysis showed that different antibiotics had clustered distributions for each strain and could be easily distinguished. Genetic, metabolic and antibiotic mechanism differences could also be deduced by the aid of further correlation analysis. For P. aeruginosa, even synergy action amid antibiotics could be ascertained. [Copyright &y& Elsevier]