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•Ti3C2Tx MXene is predicted to be a promising sensor for SF6 decomposition characteristic components.•Different terminated Ti3C2Tx MXene exhibits unequal adsorption strength to ...analytes.•Hydroxyl groups significantly promotes the adsorption strength on Ti3C2Tx MXene surface.•The changes of Ti3C2Tx conductivity are mainly induced by obvious charge transfer after the analytes adsorption.
SF6 decomposition characteristic components detection is currently one of the effective technical means for SF6 gas insulation equipment condition monitoring, and sensors are the key to achieving this goal. In this paper, two-dimensional MXene is used as a sensing material, combined with DFT method to study the adsorption behaviour of Ti3C2Tx with different termination groups (O, F, OH) on the main decomposition characteristic components of SF6 such as H2S, SO2, SOF2 and SO2F2.The most stable structure, α-model Ti3C2Tx was obtained and various gas adsorption structures were constructed and geometrically optimized. The most stable adsorption structures of different Ti3C2Tx surfaces were obtained by comparing the adsorption energy. The electron density, band structure and density of states of the adsorption system were further analyzed. The results show that target gases adsorb spontaneously on Ti3C2O2 and Ti3C2(OH)2, while on Ti3C2F2 external energy is required to form stable adsorption structures. Charge transfer induced by gas adsorption gradually decreases at the order of Ti3C2(OH)2, Ti3C2O2 and Ti3C2F2. Hydroxyl groups terminated Ti3C2Tx MXene performed better sensing ability over oxygen and fluorine terminated ones. And 2D Ti3C2(OH)2 is a promising candidate for SF6 decomposition characteristic components sensor, surpassing graphene and transition metal dichalcogenides.
Identifying the geographical origins of green teas produced in specific regions is of significance since the geographical origin of tea influences its quality and price greatly. In this work, a novel ...two-dimensional (2D) fingerprints acquired by high-performance liquid chromatography-diode array detector (HPLC-DAD) was firstly proposed to identify geographical origins of Chinese green teas. A total number of 62 chemical components were extracted from 2D HPLC-DAD fingerprints of 78 tea samples by multivariate curve resolution-alternating least squares (MCR-ALS) algorithm. Afterward, principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to classify tea samples based on the extracted components. Inspection of PCA score plots of two scaling types (UV and Par) showed that tea samples from two different geographical origins have an obvious clustering tendency. As for the OPLS-DA analysis, the Q2cum of two types-scaling OPLS-DA models are greater than 0.75, and the total recognition rates for test set are 92.86%. What's more, according to p value of t-test, VIP values, V-plot and S-plot, 17 characteristic components were screened and identified as chemical markers to distinguish between Zhejiang teas and Shandong teas. This work indicated that the proposed strategy is suitable for identifying geographical origins of Chinese green teas.
•2D HPLC-DAD fingerprints was proposed to identify geographical origins of tea.•62 chemical components were extracted from 2D HPLC-DAD fingerprints by MCR-ALS.•PCA and OPLS-DA were used to classify tea samples using the extracted components.•17 characteristic components were screened and identified as chemical markers.•There are correlations between chemical components and geographical origins of tea.
We aimed to identify the characteristic phytochemicals of safflower, Chinese sumac, and bauhinia honeys to assess their authenticity. We discovered syringaldehyde, riboflavin, lumiflavin, lumichrome, ...rhusin (1E,4E)-1,5-diphenylpenta-1,4-dien-3-one-O-cinnamoyl oxime, bitterin {4-hydroxy-4-3-(1-hydroxyethyl) oxiran-2-yl-3,5,5-trimethylcyclohex-2-en-1-one}, and unedone as characteristic phytochemicals of these three types of honeys. The average contents of syringaldehyde, riboflavin, lumiflavin, or lumichrome in safflower honey were 41.20, 5.24, 24.72, and 36.72 mg/kg; lumiflavin, lumichrome, and rhusin in Chinese sumac honey were 39.66, 40.55, and 2.65 mg/kg; bitterin, unedone, and lumichrome in bauhinia honey were 8.42, 26.33, and 8.68 mg/kg, respectively. To our knowledge, the simultaneous presence of riboflavin, lumichrome, and lumiflavin in honey is a novel finding responsible for the bright-yellow color of honey. Also, it is the first time that lumiflavin, rhusin, and bitterin have been reported in honey. We effectively distinguish pure honeys from adulterations, based on characteristic components and high-performance liquid chromatography fingerprints; thus, we seem to provide intrinsic markers and reliable assessment criteria to assess honey authenticity.
Black garlic (BG) is essentially a processed food and obtained through the transformation of fresh garlic (FG) (Allium sativum L.) via a range of chemical reactions (including the Maillard reaction) ...and microbial fermentation. This review provides the up‐to‐date knowledge of the dynamic and complicated changes in major components during the conversion of FG to BG, including moisture, lipids, carbohydrates (such as sugars), proteins, organic acids, organic sulfur compounds, alkaloids, polyphenols, melanoidins, 5‐hydroxymethylfurfural, vitamins, minerals, enzymes, and garlic endophytes. The obtained evidence confirms that BG has several advantages over FG in certain product attributes and biological properties (especially antioxidant activity), and the factors affecting the quality of BG include the type and characteristics of FG and processing technologies and methods (especially pretreatments, and processing temperature and humidity). The interactions among garlic components, and between garlic nutrients and microbes, as well as the interplay between pretreatment and main manufacturing process, all determine the sensory and nutritional qualities of BG. Before BG is marketed as a novel snack or functional food, more research is required to fill the knowledge gaps related to quantitative monitoring of the changes in metabolites (especially those taste‐active and/or biological‐active substances) during BG manufacturing to maximize BG's antioxidant, anticancer, antiobesity, anti‐inflammatory, immunostimulatory, anti‐allergic, hepatoprotective, cardioprotective and oxidative stress‐/hangover syndrome‐reducing functions, and beneficial effects on memory/nervous systems. Assessments of the quality, efficacy, and safety of BG should be performed considering the impacts of BG production conditions, postproduction handling, and intake methods.
Extracellular organic matter (EOM) produced by algal blooms in source water is detrimental to drinking water treatment processes and supplied water quality. Ozonation has been used to treat algal ...EOM, but it could not mineralize EOM effectively. In this study, mineralization and characteristics variation of EOM by vacuum ultraviolet/ozone (VUV/O3) and its sub-processes were comprehensively investigated. Results showed that EOM removal in different processes followed the order of VUV/O3 > UV/O3 > O3 > VUV > UV. For VUV/O3 process, removal efficiencies of dissolved organic carbon (DOC), UV254, protein, and polysaccharide at 50 min were 75.6%, 80.8%, 80.1%, and 78.0%, respectively, and fluorescence components received very high removal rates (≥92.8%, at 10 min). The yield of trichloromethane dropped from 102.0 to 30.1 μg/L after treating for 50 min by VUV/O3. Besides, effects of O3 dosage, initial pH, and water matrices on EOM removal in VUV/O3 process were investigated. Moreover, fluorescent molecular probe experiments confirmed that hydroxyl radical and superoxide radical were the main reactive oxygen species (ROS) in VUV/O3 process, and the transformation of ROS was proposed. The mechanism of EOM removal by VUV/O3 included VUV photolysis, direct O3 oxidation, and ROS oxidation. Furthermore, the removal of EOM in filtered water by VUV/O3 was satisfactory. All results indicated that VUV/O3 process had great application potential in treating EOM-rich filtered water.
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•VUV/O3 surpassed its sub-processes in mineralization and components removal of EOM.•VUV/O3 effectively removed fluorescence components, protein, and polysaccharide.•VUV/O3 reduced the formation of trichloromethane during EOM chlorination.•OH and O2− were main ROS during VUV/O3 process.•EOM was removed by VUV photolysis, direct O3 oxidation, and ROS oxidation.
In this paper, the thermal decomposition characteristics of epoxy resin in SF 6 was studied using simultaneous thermal analysis (TG/DSC) and gas chromatograph-mass spectrometry (GC-MS). The ...concentrations of the decomposed gas components were tested, and the method of determining whether the failure of SF 6 gas insulation equipment is caused by thermal decomposition of the insulating epoxy resin material is proposed. TG-DSC shows that the epoxy resin starts to lose weight sharply at 350 °C, and heating from 350 to 450 °C shows that the main gas products are CO 2 , SO 2 , H 2 S and SOF 2 . The concentrations of the four gases are significantly higher than where no epoxy resin is present and only pure SF 6 is injected. The concentrations of SO 2 F 2 , CF 4 and CS 2 were all kept below 0.5 ppm in the given temperature range. H 2 S is generated at about 325 °C while it can hardly be detected in the decomposition products of pure SF 6 without epoxy resin at the same temperature. Based on our observations, it is concluded that when the concentration of CO 2 reaches 5 times the sum of the concentrations of SO 2 and H 2 S, and when the concentration of H 2 S is higher than 0.5 ppm, failure of electrical equipment occurs by thermal decomposition of epoxy resin will occur.
•The mixed solvent system can be used to extract the chemical composition of the sample to the maximum extent.•The run time of each sample was 52 min by UHPLC-Q-TOF/MS.•UHPLC-Q/TOF-MS, Progenesis QI ...and Makerlynx XS software were integrated to clarify the difference of chemical components from Calculus Bovis and its mixed varieties.•The appropriate multi-response monitoring(MRM) and the characteristic marker components can be used integrately for the qualitative identification.
The method of ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC-Q/TOF-MS) was established and combined with principal component analysis (PCA) to identify natural Calculus Bovis, in vitro cultured Calculus Bovis and artificial Calculus Bovis. PCA, which was particularly powerful in dealing with multicollinearity and variables that outnumber the samples, was used to analyze the UHPLC-MS data of the processed samples, and potential markers were analyzed and described based on orthogonal partial least-squares discriminant analysis. According to the results in this study, the approach of combining UHPLC-QTOF-MS with PCA was proven to be credible and could be used to identify Calculus Bovis from in vitro cultured Calculus Bovis and artificial Calculus Bovis and to determine if there is Calculus Bovis in patented Chinese medicines that should contained Calculus Bovis medicinal materials.
Phenolic acids are thought to be beneficial for human health and responsible for vegetables' health-promoting properties. Free, conjugated, and bound phenolic acids of seven commonly consumed ...vegetables, including kidney bean, cow pea, snow pea, hyacinth bean, green soy bean, soybean sprouts and daylily, from the regions of Beijing, Hangzhou, and Guangzhou, were identified and quantified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Three vegetables, namely green soy bean, soybean sprouts, and daylily (
L.), from the Beijing region contained higher concentrations of total phenolic acids than those from the Hangzhou and Guangzhou regions. The results indicated that the phenolic acid content in the seven vegetables appeared to be species-dependent. The highest content of phenolic acids was found in daylily, followed by green soy bean, while the least amounts were identified in kidney bean and hyacinth bean. Typically, phenolic acids are predominantly found in conjugated forms. Principle component analysis (PCA) revealed some key compounds that differentiated the seven vegetables. Green soy bean, compared to the other six vegetables, was characterized by higher levels of syringic acid, ferulic acid, vanillic acid, and sinapic acid. Other compounds, particularly
-coumaric acid, neochlorogenic acid, and caffeic acid, exhibited significantly higher concentrations in daylily. In addition,
-coumaric acid was the characteristic substance in cow pea. Results from this study can contribute to the development of vegetables with specific phytochemicals and health benefits.
•High performance liquid chromatography method of non-volatile characteristic components in panax notoginseng was established.•Principal component analysis - mahalanobis distance (PCA-MD) method was ...established for the classification.•MD method could also describe the random errors in the same sample from the perspective of quantitative analysis.•Quality fluctuation of panax notoginseng samples could be determined.
In order to identify real and fake Panax notoginseng samples, the high performance liquid chromatography (HPLC) was used to analyze P. notoginseng samples of non-volatile characteristic components in P. notoginseng powder samples with 10 %, 30 %, 50 % ratio, combined with principal component analysis - mahalanobis distance (PCA-MD). The results showed that: (1) The PCA analysis showed that mahalanobis with different stem and leaf powder were divided into four categories, and the gravity center of the pattern (classification) showed that the long axis of the trend chart gradually increased with the increase of the proportion of the stem and leaf powder, and the trend chart was gradually away from the control group; (2) The mahalanobis distance indicated that the range of mahalanobis distance fluctuation (upper limit) of several P. notoginseng powder samples is 395.03∼48252.70. The larger the percentage of the stem and leaf powder in P. notoginseng samples, it is farther away from the normal P. notoginseng samples. It indicated that the product of P. notoginseng samples can be evaluated with the mahalanobis distance. The results of this study can be applied to identification and homogenization evaluation of P. notoginseng between real and fake samples.
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