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Exposure to nano-polystyrene has the potential to increase the risk of Escherichia coli O157:H7 contamination in aquatic environments.

In mammals, the enzyme cGAS senses the presence of cytosolic DNA and synthesizes the cyclic dinucleotide (CDN) 2′3′-cGAMP. This CDN binds to and activates the protein STING to trigger immunity. We recently discovered in the model organismDrosophila melanogastertwo cGAS-like receptors (cGLRs) that activate STING-dependent antiviral immunity and can produce 3′2′-cGAMP, in addition to 2′3′-cGAMP. Here we explore CDN-mediated immunity in 14 differentDrosophilaspecies covering 50 million years of evolution and report that 2′3′-cGAMP and 3′2′-cGAMP fail to control infection byDrosophilaC virus inD. serrata, D. sechelliaandD. mojavensis. Using an accurate and sensitive mass spectrometry method, we discover an unexpected diversity of CDNs produced in a cGLR-dependent manner in response to viral infection inD. melanogaster, including a novel CDN, 2′3′-c-di-GMP. We show that 2′3′-c-di-GMP is the most potent STING agonist identified so far inD. melanogasterand that this molecule also activates a strong antiviral transcriptional response inD. serrata. Our results shed light on the evolution of cGLRs in flies and provide a basis for the understanding of the function and regulation of this emerging family of PRRs in animal innate immunity.

Photocatalytic conversion of CO2 to CH3CHO is of increasing interest but confronts significant challenge in forming C–C bond and keeping a C=O bond intact throughout the process. Here, we report the selective photocatalytic hydrogenation of CO2 to CH3CHO using a modified polymeric carbon nitride (PCN) at mild conditions. The locally crystallized PCN offers a photocatalytic activity of 1814.7 μmolh-1g-1 with a high selectivity of 98.3% for CH3CHO production, and a quantum efficiency of 22.4 % at 385 nm, outperforming all the state-of-art CO2 photocatalysts. The promoted formation of the *OCCHO intermediate on the locally crystallized PCN is disclosed as the key factor leading to the high selective CH3CHO generation. The locally crystallized PCN favors spontaneously C-C coupling towards *OCCHO formation rather than *CHO protonation, thus preventing HCHO formation. This work provides a new strategy for designing carbon nitrides for high selective and sustainable conversion of CO2 into CH3CHO.

Hydrogen-bonded organic frameworks (HOFs) with multiple functions and permanent pores have received widespread attention due to their potential applications in gas adsorption/separation, drug delivery, photocatalysis, proton conduction, and other fields. Herein, we constructed a three-dimensional (3D) HOF with 1D square channels by utilizing a dual-functional tetrazolyl porphyrin ligand bearing an active center of the porphyrin core and open sites of nitrogen atoms through π-π stacking and hydrogen-bonding interaction self-assembly. The structure exhibits both solvent resistance and thermal stability, and especially, maintains these after being transformed into nanoparticles. Meanwhile, the active sites exposed on the inner wall of the pores can interact well with the photoactive cationic dye molecules to form an effective host-guest (H-G) system, which can realize boosted photosensitized singlet oxygen (

Two-dimensional gas chromatography (2D GC)���quadrupole time-of-flight mass spectrometry (QTOFMS) combined with derivatization was applied to determine naphthenic acids (NAs) in oil sand processed water (OSPW). Using the excellent resolution of 2D GC and mass resolution of QTOFMS with derivatization, 8 cyclohexane carboxylic acid isomers, 18 methylcyclohexyl carboxylic acid isomers, and 18 methylcyclohexyl acetic acid isomers were identified. Linear relationships across wide concentration ranges were established with correlation coefficients (R2) of 0.9995, 0.9992, and 0.9990, for cyclohexanecarboxylic acid, 4-methylcyclohexanecarboxylic acid, and 4-methylcyclohexane acetic acid. The precision, expressed as the relative standard deviation (RSD, n = 5), was from 7. 7���9.5% with recoveries between 72.0% and 84.9%. This method was applied to analyze sewage and showed high concentrations of naphthenic acids in untreated samples.

Emerging contaminants (ECs), especially antibiotics, have significantly polluted the environment and threaten the living circumstance of organisms. Environmental metabolomic has emerged to investigate the sublethal effects of ECs. However, lacking noninvasive and real-time sample pretreatment techniques restricts its development in environmental toxicology. Hence, in this study, a real-time and in vivo untargeted analytical technique towards microbial endogenous metabolites was developed via a novel composite solid-phase microextraction (SPME) fiber of ZIF-67 and polystyrene to realize the high-coverage capture of living gut microbial metabolites. To reveal the exposure risks of typical antibiotic - norfloxacin (NFX) to gut bacteria, four representative bacteria were exposed to NFX at environmentally relevant levels. Using the proposed SPME fiber, 70 metabolites were identified to obtain an apparent metabolic separation feature between control and NFX-treated (10 ng/mL) microbial groups, which revealed that the low environmental relevant concentration of NFX would affect normal metabolism of gut bacteria. Additionally, NFX exhibited species-specific toxic effects on microbial growth, especially Escherichia coli displaying a distinct dose-dependent trend. Antioxidative enzymatic activities results demonstrated that beneficial bacteria maintained the state of oxidative stress while symbiotic bacteria suffered from oxidative stress injury under NFX contamination, further corroborating its impact on human intestinal health. This study highlights the suitability of in vivo SPME in the field of metabolite extraction and simultaneously possesses a brilliant application foreground in the environmental metabolomics.

The Rosa chinensis cultivars Rosa Lvye, Rosa Knock out, Rosa Parade and Slater’scrimson China were analyzed for the volatile chemical composition in their flower petals. Headspace solid phase micro...

Microglia-mediated neuroinflammation in response to injurious self and non-self-stimuli exerts detrimental effects on neurons, which may lead to cognitive impairment. Luteolin, a typical kind of natural flavonoid in honeysuckle, chrysanthemum, and Herba Schizonepetae, is widely recognized to be anti-inflammatory and antioxidant against peripheral inflammation. However, its protective effect against inflammation-induced cognitive impairment is currently unknown. In this paper, we investigated the relief potential of luteolin against lipopolysaccharide (LPS)-induced cognitive impairment and neuroinflammation and its possible anti-inflammatory mechanisms in lipopolysaccharide-stimulated BV2 microglia cells. In this study, luteolin ameliorated LPS-induced cognitive impairments, indicated by behavioral performance of neuroinflammatory model mice in Morris water maze tests. Protein analyses and histological examination also revealed protective effect of luteolin against neuronal damage, through inhibiting overproduction of inflammatory cytokines in both hippocampus and cortex of mice. We also observed luteolin in vitro significantly suppressed the levels of pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF-α) and interleukin-1 β (IL-1β), and inflammatory mediators like nitric oxide. Taken together, these results demonstrated luteolin was effective in alleviating cognitive impairment and limited neuronal damage via inhibiting the release of inflammatory mediators, suggesting luteolin is potential for further therapeutic research of neuroinflammation-related neurodegenerative diseases.

The volatile compounds in Rosa rugosa ���Zi Zhi���, R. rugosa ���Feng Hua���, and R. cv ���Crimson Glory��� from three regions were determined by two-dimensional gas chromatography with quadrupole time-of-flight mass spectrometry coupled with knitting aromatic polymer ��� polydopamine (KAP@PDA) solid-phase microextraction. 82 compounds were identified by peak matching and retention indices, and R. cv ���Crimson Glory��� contained the most volatile components. D-Limonene (up to 5131 ��g kg���1), benzyl alcohol (up to 16,510 ��g kg���1), benzeneacetaldehyde (up to 13,820 ��g kg���1), phenylethyl alcohol (up to 49,020 ��g kg���1) and citronellol (up to 7129 ��g kg���1) were the major constituents in all R. rugosa species. In addition, benzaldehyde was highly abundant in R. cv ���Crimson Glory��� (up to 23,130 ��g kg���1). The primary volatile components responsible for the differences among the three R. rugosa cultivars and regions were distinguished by orthogonal partial least-squares discriminant analysis. The results suggested that phenylethyl alcohol contributed the most in distinguishing aroma quality for R. rugosa cultivars and those from different regions.

Microplastics (MPs) can adsorb toxic chemicals in biological or environmental matrixes and thus influence their behavior and availability. In order to investigate how the combined pollution of MPs and toxic organic chemical influence microbial growth and metabolism, Escherichia coli (E. coli) was grown in a complex, well-defined media and treated with polystyrene microplastics (PS MPs) and dichloro-diphenyl-tricgloroethane (DDT) at human relevant concentration levels. In vivo metabolites captured by a novel solid phase microextraction (SPME) probe, were used to reflect the metabolic dysregulation of E. coli under different pollution stresses. Results showed that the toxic effect of DDT displayed a distinct dose-dependent phenomenon while the existence of PS decreased the growth and metabolic interference effect of DDT on E. coli. Adsorption results revealed a mechanism that PS weakened the adverse impact of DDT by decreasing its free concentration in the treated culture media. Tricarboxylic acid (TCA) cycle related enzymes activities and antioxidant defense related substances of E. coli also proved the mechanism. The current study is believed to broaden our understanding of the ecotoxicity of MPs with toxic organic chemicals on microorganism.

Foodborne diseases incurred by pathogenic bacteria are one of the major threats in food safety, and thus it is important to develop facile and effective recognition methodology of pathogens in food. Herein, a new automatic approach for detection of in vivo volatile metabolites emitted from foodborne pathogens was proposed by coupling solid phase microextraction (SPME) technique with a comprehensive two-dimensional gas chromatography quadrupole time-of-flight mass spectrometry (GC × GC-QTOFMS). A novel polymer composite based SPME probe which possessed high-coverage of microbial metabolites was utilized in this contribution to realize the sensitive extraction of untargeted metabolites. As a result, a total of 126 in vivo metabolites generated by the investigated pathogens were detected and identified, with 33, 29, 25, 21 and 18 volatile metabolites belonging to Shigella sonnei, Escherichia coli, Salmonella typhimurium, Vibrio parahaemolyticus and Staphylococcus aureus, respectively. Multivariate statistical analyses were applied for further analysis of metabolic data and separation of responsive metabolic features among different microbial systems were found, which were also successfully verified in foodstuffs contaminated by microorganisms. The growth trend of the potential volatile markers of each pathogen in food samples kept consistent with that of the pure strain incubated in medium during the whole incubation time. This study promotes the application of SPME technology in microbial volatile metabolomics and contributes to the development of new approaches for foodborne pathogens recognition.

A rapid and sensitive method for analyzing trace β-blockers in complex biological samples, which involved magnetic solid-phase extraction (MSPE) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), was developed. Novel nanosilver-functionalized magnetic nanoparticles with an interlayer of poly(3,4-dihydroxyphenylalanine) (polyDOPA@Ag-MNPs) were synthesized and used as MSPE adsorbents to extract trace β-blockers from biological samples. After extraction, the analytes loaded on the polyDOPA@Ag-MNPs were desorbed using an organic solvent and analyzed by FTICR-MS. The method was rapid and sensitive, with a total detection procedure of less than 10 min as well as limits of detection and quantification in the ranges of 3.5-6.8 pg/mL and 11.7-22.8 pg/mL, respectively. The accuracy of the method was also desirable, with recoveries ranging from 80.9% to 91.0% following the detection of analytes in human blood samples. All the experimental results demonstrated that the developed MSPE-FTICR-MS method was suitable for the rapid and sensitive analysis of trace β-blockers in complex biological samples.

Herein, a heterogeneous pore decoration strategy on a hydrophobic microporous polymer is presented. The smaller pores in the material were completely decorated with hydrophilic polydopamine while most of the larger ones survived after modification, leading to its hydrophobic-hydrophilic hybrid properties and high-coverage capture ability of metabolites.

Tobacco (Nicotiana tabacum), is a world’s major non-food agricultural crop widely cultivated for its economic value. Among several color change associated biological processes, plastid pigment metabolism is of trivial importance in postharvest plant organs during curing and storage. However, the molecular mechanisms involved in carotenoid and chlorophyll metabolism, as well as color change in tobacco leaves during curing, need further elaboration. Here, proteomic analysis at different curing stages (0 h, 48 h, 72 h) was performed in tobacco cv. Bi’na1 with an aim to investigate the molecular mechanisms of pigment metabolism in tobacco leaves as revealed by the iTRAQ proteomic approach. Our results displayed significant differences in leaf color parameters and ultrastructural fingerprints that indicate an acceleration of chloroplast disintegration and promotion of pigment degradation in tobacco leaves due to curing. In total, 5931 proteins were identified, of which 923 (450 up-regulated, 452 down-regulated, and 21 common) differentially expressed proteins (DEPs) were obtained from tobacco leaves. To elucidate the molecular mechanisms of pigment metabolism and color change, 19 DEPs involved in carotenoid metabolism and 12 DEPs related to chlorophyll metabolism were screened. The results exhibited the complex regulation of DEPs in carotenoid metabolism, a negative regulation in chlorophyll biosynthesis, and a positive regulation in chlorophyll breakdown, which delayed the degradation of xanthophylls and accelerated the breakdown of chlorophylls, promoting the formation of yellow color during curing. Particularly, the up-regulation of the chlorophyllase-1-like isoform X2 was the key protein regulatory mechanism responsible for chlorophyll metabolism and color change. The expression pattern of 8 genes was consistent with the iTRAQ data. These results not only provide new insights into pigment metabolism and color change underlying the postharvest physiological regulatory networks in plants, but also a broader perspective, which prompts us to pay attention to further screen key proteins in tobacco leaves during curing.

For decades, researches have been involving in improving and optimizing solid-phase microextraction (SPME) technique to fit the growing environmental analysis demand. But it is more significant now to introduce meaningful information into the analysis line instead of improving every step in SPME. Herein, we design a carbon dots (CDs) based SPME platform and report its unique application in selective early screening and sensitive detection of 2-nitroaniline. The fluorescence quenching state of the CDs fiber after extraction could be used to prejudge whether an environmental sample contains 2-nitroaniline exceeding the maximum permitted level (30 μg L−1) regulated by the Chinese Ministry of Environmental Protection or not. Photo-induced electron transfer (PET) is believed to be the primary quenching route that leads to electron transfer from the electron-rich CDs to the electron-deficient analyte. A preliminary in vivo study on Daphnia magna and a 2-nitroaniline assay in environmental water and biofluid samples suggested the safety and the excellent qualitative ability of the proposed platform. As a result, the innovative incorporation of fluorescence sensing and SPME not only achieves the information imbedding of environmental analysis system, but also combines the advantages of two techniques including early visual-screening, reusability (≥50 times), high specificity and excellent quantitative ability (detection limit: 0.011 μg L−1). We believe this study can open new avenues in the field of environmental toxicant monitoring.

Polyamines are ubiquitous polycationic molecules that play a key role in many biological processes such as nucleic acid metabolism, protein synthesis, cell growth, and nicotine synthesis precursors. This work describes a rapid, sensitive, convenient, green, and cost-effective method for the determination of polyamines in Nicotiana tabacum by ultra high performance liquid chromatography with photodiode array detection. The analytes were derivatized with 3,5-dinitrobenzoyl chloride at low temperature (about 4°C) and then extracted with vortex-assisted liquid-liquid microextraction. The experimental designs based on quarter-fractional factorial design and Doehlert design were used to screen and optimize the important factors in microextraction process. Under the optimal conditions, the method was linear over 0.05-8.00 μg/mL with an r(2) ≥ 0.992 and exhibited good repeatability and reproducibility less than 6.0 and 6.9%, respectively. The limit of detection ranged between 0.013 and 0.029 μg/g. The newly developed method was successfully employed to analyze different leaf samples of Nicotiana tabacum, among which the polyamines contents were found to be very different. Moreover, tyramine, 1,3-diaminopropane, homospermidine, and canavalmine were tentatively identified with the electrospray ionization quadrupole time-of-flight mass spectrometry. To our knowledge, this is the first report of identification of canavalmine in Nicotiana Tabacum.

Psoriasis is considered as a common chronic immune-mediated skin disorder characterized by abnormal keratinocyte proliferation. Luteolin, an anti-inflammatory natural flavonoid with well-accepted inhibition effect against keratinocyte proliferation, was hypothesized to have a potential therapeutic effect for psoriasis. In this paper, we investigated the relieving effect of luteolin against imiquimod-induced psoriasis-like lesions on BALB/c mice and its possible anti-inflammatory mechanisms in lipopolysaccharide-stimulated macrophages (RAW264.7 cells). We found that luteolin ameliorated psoriasis-like skin lesions, suppressed the cutaneous infiltration of macrophages, T cells and neutrophils, and downregulated the expression of cytokines like IL-6, IL-1β, TNF-α, IL-17A and IL-23 in both skin lesions and eyeball blood of model mice. In vitro, we observed luteolin significantly suppressed the levels of psoriasis-related pro-inflammatory cytokines, such as IL-17A, IL-6, TNF-α and IL-23, and inflammatory mediators like nitric oxide NO, inducible NOS, COX-2 in RAW264.7 cells. The anti-inflammatory activity was accomplished by inhibiting NF-κB expression and activation. This study demonstrates luteolin is effective in alleviating psoriasis-like skin lesions and downregulating inflammatory response via NF-κB pathway, suggesting luteolin as a potential molecule for further therapeutic research of inflammation-related skin diseases like psoriasis.

At present, researches on various areas have been benefited from the advancement in solid-phase microextraction (SPME) technique, which covers a wide scope of analytes with different properties, facilitates on-site sampling and sample preparation, allows automated operation with high sample throughput, and facilitates long-range monitoring. As the scope of SPME grows, further increases in the specificity, speed and efficiency of this technique are still urgently needed. Application of auxiliary energies is one of the efficient strategies to achieve the aforementioned purpose. This review offers a brief discussion concerning several physical assistive technologies of SPME (e.g. vacuum, ultrasound, microwave, electrical driving force, magnetism, etc.) with respect to targeted or untargeted analysis of different substances in environmental, biological and food samples. Achievements, limitations, and future trends of these applications are also discussed. This review article is believed to be conductive to future applications of auxiliary energy assisted SPME methods in various fields.

Tobacco (Nicotiana tabacum), is a world&rsquo, s major non-food agricultural crop widely cultivated for its economic value. Among several color change associated biological processes, plastid pigment metabolism is of trivial importance in postharvest plant organs during curing and storage. However, the molecular mechanisms involved in carotenoid and chlorophyll metabolism, as well as color change in tobacco leaves during curing, need further elaboration. Here, proteomic analysis at different curing stages (0 h, 48 h, 72 h) was performed in tobacco cv. Bi&rsquo, na1 with an aim to investigate the molecular mechanisms of pigment metabolism in tobacco leaves as revealed by the iTRAQ proteomic approach. Our results displayed significant differences in leaf color parameters and ultrastructural fingerprints that indicate an acceleration of chloroplast disintegration and promotion of pigment degradation in tobacco leaves due to curing. In total, 5931 proteins were identified, of which 923 (450 up-regulated, 452 down-regulated, and 21 common) differentially expressed proteins (DEPs) were obtained from tobacco leaves. To elucidate the molecular mechanisms of pigment metabolism and color change, 19 DEPs involved in carotenoid metabolism and 12 DEPs related to chlorophyll metabolism were screened. The results exhibited the complex regulation of DEPs in carotenoid metabolism, a negative regulation in chlorophyll biosynthesis, and a positive regulation in chlorophyll breakdown, which delayed the degradation of xanthophylls and accelerated the breakdown of chlorophylls, promoting the formation of yellow color during curing. Particularly, the up-regulation of the chlorophyllase-1-like isoform X2 was the key protein regulatory mechanism responsible for chlorophyll metabolism and color change. The expression pattern of 8 genes was consistent with the iTRAQ data. These results not only provide new insights into pigment metabolism and color change underlying the postharvest physiological regulatory networks in plants, but also a broader perspective, which prompts us to pay attention to further screen key proteins in tobacco leaves during curing.

Compounds extracted from essential oil of the Lavandula angustifolia by steam distillation were analysed by gas chromatography with quadrupole time-of-flight mass spectrometry (GC-QTOF/MS) and their anti-inflammatory activity were tested by a 12-O-tetradecanoyl phorbol-13-acetate (TPA)-induced inflammation method. The GC-QTOF/MS analysis identified 50 constituents, all representing 96.89% of the essential oil total composition. In particular, match factors, accurate mass and retention indexes were used to improve the accuracy of qualitative results. The main compounds identified were linalyl acetate (28.89%), linalool (24.30%), caryophyllene (7.89%), (E)-3,7-dimethylocta-1,3,6-triene (4.64%), 4-terpineol (4.04%), acetic acid lavandulyl ester (3.49%), borneol (2.60%) and eucalyptol (2.05%). Regarding anti-inflammatory activity, the essential oil was effective against the TPA-induced inflammation in mouse ear. The inhibition effect of essential oils (100 mg/kg) on TPA-induced mouse ear edema was about 58.66%. Meanwhile, the expression levels of transcription factor, nuclear factor kappa-B (NF-κB), inflammatory cytokine, cyclooxygenase-2 (COX-2) and tumor necrosis factor (TNF-α) were also decreased significantly. The results in this study show essential oil had a better anti-inflammatory activity than that of ibuprofen at the same dosage, which demonstrated a great potential value in application.

A method involving comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry was developed and applied to the analysis of nitrogenous organic compounds present in mainstream cigarette smoke trapped on self-designed equipment. The samples were prepared using low-temperature solvent extraction under liquid nitrogen and analyzed by comprehensive two-dimensional gas chromatography with high-resolution time-of-flight mass spectrometry. Important experimental parameters, such as the type and volume of the extraction solvent and flow rate of smoking, were optimized to improve the analysis parameter. The results indicated that 180 mL of diethyl ether in the low-temperature solvent extraction apparatus system with a 4 mL/min smoke flow rate were the optimal conditions. Then, 85 nitrogenous organic compounds were identified and quantified using a mass spectral library search, accurate mass ion and N-rules of a molecular formula for nitrogen compounds. Finally, a comparison of the low temperature solvent extraction method and Cambridge filter pad method indicated that more peaks, a higher peak volume and better repeatability were obtained using the low-temperature solvent extraction method.

This work describes a rapid, stable, and accurate method for determining the free amino acids, biogenic amines, and ammonium in tobacco. The target analytes were extracted with microwave-assisted extraction and then derivatized with diethyl ethoxymethylenemalonate, followed by ultra high performance liquid chromatography analysis. The experimental design used to optimize the microwave-assisted extraction conditions showed that the optimal extraction time was 10 min with a temperature of 60°C. The stability of aminoenone derivatives was improved by keeping the pH near 9.0, and there was no obvious degradation during the 80°C heating and room temperature storage. Under optimal conditions, this method showed good linearity (R2 > 0.999) and sensitivity (limits of detection 0.010-0.081 μg/mL). The extraction recoveries were between 88.4 and 106.5%, while the repeatability and reproducibility ranged from 0.48 to 5.12% and from 1.56 to 6.52%, respectively. The newly developed method was employed to analyze the tobacco from different geographical origins. Principal component analysis showed that four geographical origins of tobacco could be clearly distinguished and that each had their characteristic components. The proposed method also showed great potential for further investigations on nitrogen metabolism in plants.

Glycosidically bound aroma compounds in three different types of tobacco were investigated. After isolation of extracts obtained by Amberlite XAD-2 adsorption and ethyl acetate elution, glycosides were analyzed after enzymatic hydrolysis by gas chromatography-mass spectrometry (GC-MS) or directly after trifluoroacetylated (TFA) derivatization by GC-MS in electron ionization (EI) and negative chemical ionization (NCI) mode. In total 21 bound aglycones were identified by β-glucosidase hydrolysis. These aglycones mainly consisted of C13-norisoprenoids, aromatic components and sesquiterpenoids. Additionally, with the aid of enzymatic hydrolysis, 15 β-d-glucopyranosides and 1 β-d-rutinoside were tentatively identified by TFA derivatization. TFA method was validated by repeatability and successfully employed to analyze different types of tobacco. Principal component analysis (PCA) was carried out on identified glycoside variables to visualize the difference between the tobacco types and the relationship between the glycoside variables and the tobacco types was established.

Polyamines are ubiquitous polycationic molecules that play a key role in many biological processes such as nucleic acid metabolism, protein synthesis, cell growth, and nicotine synthesis precursors. This work describes a rapid, sensitive, convenient, green, and cost-effective method for the determination of polyamines in Nicotiana tabacum by ultra high performance liquid chromatography with photodiode array detection. The analytes were derivatized with 3,5-dinitrobenzoyl chloride at low temperature (about 4°C) and then extracted with vortex-assisted liquid-liquid microextraction. The experimental designs based on quarter-fractional factorial design and Doehlert design were used to screen and optimize the important factors in microextraction process. Under the optimal conditions, the method was linear over 0.05-8.00 μg/mL with an r(2) ≥ 0.992 and exhibited good repeatability and reproducibility less than 6.0 and 6.9%, respectively. The limit of detection ranged between 0.013 and 0.029 μg/g. The newly developed method was successfully employed to analyze different leaf samples of Nicotiana tabacum, among which the polyamines contents were found to be very different. Moreover, tyramine, 1,3-diaminopropane, homospermidine, and canavalmine were tentatively identified with the electrospray ionization quadrupole time-of-flight mass spectrometry. To our knowledge, this is the first report of identification of canavalmine in Nicotiana Tabacum.

A method suitable for qualitative and quantitative analysis was developed and validated for volatile flavour components in flue-cured tobacco. The samples were prepared with headspace solid-phase microextraction (HS-SPME) and analyzed by comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOFMS). Important experimental parameters, such as the column combinations, the type of SPME fibres and headspace temperatures, were optimized to improve separation and precision. The results showed that divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fibre at a headspace temperature of 70 °C, along with DB-1MS and DB-wax columns were the best conditions. The 93 compounds of interest were identified and quantified by the match factor and internal standard phenylethyl acetate and the relative standard deviation for most compounds was less than 22.7%. Finally, the developed analytical method was applied to the classification of different flue-cured tobacco samples from different geographical origins and satisfactory results were achieved.

A reliable, sensitive and rapid method for determination of eight alkaloids in flue-cured tobacco by dual-column-dual-detector gas chromatography with nitrogen chemiluminescence detection (GC-NCD) has been established. At first, the extraction effects of several factors such as solid to liquid ratio, extraction time, sodium hydroxide solution volume and sodium hydroxide solution mass fraction on the extraction efficiency were simultaneously investigated using an orthogonal array design (OAD). Then, the NCD was compared to other detectors and showed some unique advantages. The analytical method met the strict quantitative requirement by optimizing chromatographic conditions and using dual-column confirmation. Finally, the performance of the proposed method was tested for the extraction and determination of the eight alkaloids in flue-cured tobacco and satisfactory results were achieved.