查找使用阿拉丁产品的科研文献

Magnetic C60 nanospheres based solid-phase extraction coupled with isotope dilution gas chromatography–mass spectrometry method for the determination of sixteen polycyclic aromatic hydrocarbons in Chinese herbal medicines

Dian-Bing Zhou,Fang Han,Lei Ding,Wei Song,Ya-Ning Lv,Yan-Yun Hu,Yu-Xin Liu,Xuan Sheng,Ping Zheng

C 60 -based magnetic nanospheres were synthesized by coating Fe 3 O 4 nanospheres with silica, then modifying with 3-aminopropyltriethoxysilane as a linker and a C 60 fullerene stationary phase. The morphologies, magnetic properties, infrared absorption and carbon content of magnetic nanospheres were studied by TEM, VSM, FTIR and carbon and sulfur analyzer. The magnetic nanospheres were employed for the magnetic solid-phase extraction (MSPE) of 16 polycyclic aromatic hydrocarbons (PAHs) in nine Chinese herbal medicines. The analyses were conducted by isotope dilution gas chromatography–mass spectrometry. The main parameters influencing the extraction, including extraction solvent, adsorbent amount, and extraction time were optimized. Method validation showed that the limit of detection (LOD) was 0.02–0.11 µg/kg, and the limit of quantification (LOQ) was 0.07–0.36 µg/kg. The spiked recoveries rates for 16 PAHs in white peony root were 84.7–107.2%. The relative standard deviation (RSD) was 1.7–8.4%. The established method was further used for the determination 16 PAHs in nine Chinese herbal medicines. Total content of 16 PAHs varied from 73.6 µg/kg (fructus lycii) to 2172.6 µg/kg (astragalus root). The results indicate that the pollution of PAHs in Chinese herbal medicines is serious. The established method can effective detect PAHs contamination in Chinese herbal medicines.

Highly efficient Cu/CeO2-hollow nanospheres catalyst for the reverse water-gas shift reaction: Investigation on the role of oxygen vacancies through in situ UV-Raman and DRIFTS

Yudong Zhang,Long Liang,Ziyang Chen,Jinjun Wen,Wen Zhong,Sibei Zou,Mingli Fu,Limin Chen,Daiqi Ye

Self-assembled CeO 2 with 3D hollow nanosphere, nanoparticle and nanocube morphologies were prepared and used to support Cu particles. The obtained samples (denoted as Cu/CeO 2 -hs, Cu/CeO 2 -np and Cu/CeO 2 -nc, respectively) were tested for the reverse water-gas shift (RWGS) reaction. Under the reaction conditions, V (H 2 ): V (CO 2 ) = 3:1 and weight hourly space velocity (WHSV) = 300,000 mL g −1  h −1 , the Cu/CeO 2 -hs sample exhibited the best catalytic performance among the as-prepared catalysts. In order to reveal the key factors affecting the catalytic performance, the physicochemical properties of the catalysts were analyzed by XRD, BET, SEM, TEM, H 2 -TPR, quasi in-situ XPS and in situ UV-Raman techniques. The results point out that the particle size of Cu is not the rate-determining factor while the amount of surface oxygen vacancies is highly correlated with the catalytic reaction rate. In situ UV-Raman and in situ DRIFTS experiments indicate the formation of bidentate carbonate and formate species on oxygen vacancy sites which is thought to be the key intermediates for the RWGS reaction. These findings unravel the crucial roles of surface oxygen vacancies on CO 2 adsorption and activation and also highlight a feasible way for the design of highly efficient catalysts for the important RWGS reaction in chemical industry.

A Comparative Study of Gas-phase Fluorination and Nano-Al2O3 Doping on Space Charge Behavior and Trap Level in Epoxy Resin

Zijia Shen,Feipeng Wang,Muhammad Zeeshan Khan,Zhengyong Huang,Li He,Yushuang He,Jian Li

The Effects of Mass Transfer on the Determination of Gas–Liquid Reaction Kinetics in a Stirred Cell Reactor: In the Case of CO2 Absorption by Aqueous Alkanolamine Solution

Chongchong Lu,Ming Chen,Xiao Luo,Zhiwu Liang

In order to be able to understand and compensate for the mass transfer effects on the reaction kinetics that typically occur in these studies, the influences of diffusion and gas phase resistance on the measurement of kinetics have been investigated. Carbon dioxide (CO2) absorption into monoethanolamine (MEA) and N-methyldiethanolamine (MDEA) have been taken as the fast and slow reaction cases in this work. The inflection point between diffusion control and reaction control regions was found in the fast reaction case but not in the slow one. Further, there is a low critical value of Pinert, below which its effect can be ignored, in the fast reaction system. Conversely, the critical value of Pinert in the slow reaction system is higher. Additionally, credible intrinsic kinetics of the both systems have been obtained under optimum conditions, expanding the temperature range to lower than what is available in the literature.

Dispersive micro-solid phase extraction using cotton based carbon fiber sorbent for the determination of three polycyclic aromatic hydrocarbons in tea infusion by gas chromatography-quadrupole mass spectrometry

Zhihong Shi,Jing Jiang,Weiyue Pang,Hongyu Ma,Xiaoxue Chu,Can Zhou,Hongyi Zhang

In this study, carbon fibers (CFs) were used as sorbent material for the dispersive micro-solid phase extraction (d-μSPE) of anthracene , acenaphthene and phenanthrene from tea infusion samples prior to gas chromatography-quadrupole mass spectrometric detection. CFs were obtained by carbonizing cotton at 800 °C under the protection of nitrogen for 4 h. After characterization by the scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction and N 2 adsorption-desorption, 20 mg of CFs were used to effectively adsorb PAHs in 5 min from 10 mL of tea infusion samples, 2 mL of toluene was used as desorbent . Under the optimum conditions, good linearity was obtained with R 2 between 0.9996 and 0.9998. The limits of detection were in the range of 0.012–0.014 μg/L. RSD values for intra- and inter-day precision were ≤6.7% and ≤7.8%, respectively. In this work, cotton based CFs were prepared in a solventless and green way and the CFs based d-μSPE procedure was simple, rapid and cost-effective, with no need of column-packing. The proposed method has been successfully applied to the analysis of PAHs in three kinds of tea infusion samples.

The fabrication of poly (polyethylene glycol diacrylate) monolithic porous layer open tubular (mono-PLOT) columns and applications in hydrophilic interaction chromatography and capillary gas chromatography for small molecules

Feng Chang,Yunfang Yue,Zihui Yang,Si Huang,Zhihua Liu,Kunmiao Wang,Yan Peng,Yingzhuang Chen,Ming Ma,Bo Chen

The easy shrinkage and swelling of polymer monolithic column when exposed to mobile phase with different polarity is a problem that cannot be ignored. To overcome this drawback, a convenient aqueous two-phase polymerization approach was used to prepare poly (polyethylene glycol diacrylate, PEGDA) monolithic porous layer open tubular (mono-PLOT) columns (150 μm). The poly(PEGDA) mono-PLOT column with homogeneous polymer porous layer was synthesized successfully. A maximum plate number of 41,500 plates per meter for allyl thiourea was obtained under a velocity of 1.8 mm/s. Several kinds of polar molecule were separated on the proposed mono-PLOT column and a typical hydrophilic interaction retention mechanism was observed. High speed separation of benzoic acids was also carried out, baseline separation of five benzoic acids was successfully achieved within 5 min with a 70 cm mono-PLOT column at 50°C. Furthermore, the resulting PLOT column was also successfully applied to separate standard analytes of three DNA oxidative damage products and RNA-modified nucleosides and four chlorophenols. At last, the column could separate alcohols, alkanes, and aromatic isomers via GC. It had more than 20,000 plates per meter for butanol – higher than commercial coatings open tubular columns.

Hollow fiber-protected metal–organic framework materials as micro-solid-phase extraction adsorbents for the determination of polychlorinated biphenyls in water samples by gas chromatography-tandem mass spectrometry

Hao Zang,Jin-Peng Yuan,Xiang-Feng Chen,Chang-An Liu,Chuan-Ge Cheng,Ru-Song Zhao

A novel modified micro-solid-phase extraction (μ-SPE) device was developed in this study using hollow fiber-protected metal–organic framework (MOF) materials as sorbents. Polychlorinated biphenyls (PCBs) were used as model compounds. Gas chromatography with tandem mass spectrometry (GC-MS/MS) was used for sample quantification and detection. Important factors that affect the extraction were investigated and optimized in detail. The developed μ-SPE-GC-MS/MS method had low limits of detection (0.15 ng L−1 to 0.63 ng L−1, S/N = 3), relatively high precision (relative standard deviation <13.5%), and good linearity in the range of 5–1000 ng L−1 for seven PCBs under optimized conditions. The μ-SPE device was more robust than the traditional “envelope” type device and could be used for more than 80 replicate extractions without performance loss. The proposed method was successfully used for analyzing environmental water samples. The results obtained in this paper demonstrate that the hollow fiber protection of MOF materials is an effective type of μ-SPE for aromatic pollutant extraction in water samples.

Ultrasound-assisted low-density solvent dispersive liquid–liquid microextraction for the simultaneous determination of 12 new antidepressants and 2 antipsychotics in whole blood by gas chromatography–mass spectrometry

Xiujuan Chen,Shuiqing Zheng,Jian Le,Zheyuan Qian,Runsheng Zhang,Zhanying Hong,Yifeng Chai

Antidepressant drugs are widely used in the treatment of different psychiatric disorders, as well as in conjunction with antipsychotics for the treatment of major depressive disorder. In this study, a simple and rapid ultrasound-assisted low-density solvent dispersive liquid–liquid microextraction (UA-LDS-DLLME) method was developed for the simultaneous determination of 12 new antidepressants (norfluoxetine, fluoxetine, fluvoxamine, agomelatine, mirtazapine, moclobemide, melitracen, N-desmethylmirtazapine, maprotiline, sertraline, citalopram, paroxetine) and 2 antipsychotics (clozapine and haloperidol) in human whole blood by gas chromatography–mass spectrometry (GC–MS). Different parameters affecting the UA-LDS-DLLME were optimized and the optimal conditions were as follows: 100   μL of toluene as extraction solvent, extraction pH 12 and 3   min of ultrasound stirring. Good linearity ( R 2   ≥   0.991) was obtained at the concentration range of 15–1500   ng/mL for norfluoxetine, fluoxetine, fluvoxamine, melitracen, maprotiline and citalopram, and 5–500   ng/mL for agomelatine, mirtazapine, moclobemide, N-desmethylmirtazapine, sertraline, paroxetine, clozapine and haloperidol. The intra-day and inter-day precision were all less than 10%, and accuracy of intra-day and inter-day were in the range of −12.7% to 7.9% and −13.9 to 11.8%, respectively. The extraction recoveries of most analytes were more than 60%. The UA-LDS-DLLME/GC–MS method was demonstrated with acceptable precision, accuracy and good specificity for the simultaneous determination of 12 antidepressants and 2 antipsychotics, and has been successfully applied in a real case.

Electrodeposition of self-assembled poly(3,4-ethylenedioxythiophene) @gold nanoparticles on stainless steel wires for the headspace solid-phase microextraction and gas chromatographic determination of several polycyclic aromatic hydrocarbons

Liu Yang,Jie Zhang,Faqiong Zhao,Baizhao Zeng

In this work, a novel poly(3,4-ethylenedioxythiophene)@Au nanoparticles (PEDOT@AuNPs) hybrid coating was prepared and characterized. Firstly, the monomer 3,4-ethylenedioxythiophene was self-assembled on AuNPs, and then electropolymerization was performed on a stainless steel wire by cyclic voltammetry. The obtained PEDOT@AuNPs coating was rough and showed cauliflower-like micro-structure with thickness of ∼40   μm. It displayed high thermal stability (up to 330   °C) and mechanical stability and could be used for at least 160 times of solid phase microextraction (SPME) without decrease of extraction performance. The coating exhibited high extraction capacity for some environmental pollutants (e.g. naphthalene, 2-methylnaphthalene, acenaphthene, fluorene and phenathrene) due to the hydrophobic interaction between the analytes and PEDOT and the additional physicochemical affinity between polycyclic aromatic hydrocarbons and AuNPs. Through coupling with GC detection, good linearity (correlation coefficients higher than 0.9894), wide linear range (0.01–100   μg   L −1 ), low limits of detection (2.5–25   ng   L −1 ) were achieved for these analytes. The reproducibility (defined as RSD) was 1.1–4.0% and 5.8–9.9% for single fiber (n   =   5) and fiber-to-fiber (n   =   5), respectively. The SPME-GC method was successfully applied for the determination of three real samples, and the recoveries for standards added were 89.9–106% for lake water, 95.7–112% for rain water and 93.2–109% for soil saturated water, respectively.

Examining the effects of processing techniques on the quality of hawk tea through liquid chromatography–tandem mass spectrometry and two-dimensional gas chromatography–time-of-flight mass spectrometry

Gong Feng,Jiacheng Li,Jun Liu,Rong Tan

Processing techniques are critical factors influencing the quality of hawk tea, yet systematic studies on their effects are limited. This study investigates the impact of four key processing procedures—fixation, reddening, fermentation, and compressing—using sensory evaluation, LC-MS/MS, and GC × GC-TOF-MS. Analysis identified 6951 non-volatile metabolites, including 107 marker metabolites, primarily in flavonoid synthesis and degradation pathways. Fermentation increased sweetness and richness by enhancing sugars and amino acid content, while significantly reducing flavonoid levels. Reddening improved flavor, color, and retained more beneficial flavonoids. Volatile analysis detected over 1800 compounds, including 398 volatile marker metabolites. Fermentation increased alcohols and heterocyclic compounds, reducing hydrocarbons and ketones. Additionally, 26 camphoraceous and 12 pungent aroma compounds characteristic of hawk tea were identified, and an aroma-flavor correlation map was established. By elucidating the impact of processing methods on its chemical and sensory properties, this study lays the groundwork for targeted quality control of hawk tea.

A new kind of nanohybrid poly(tetradecyl methyl-acrylate)-graphene oxide as pour point depressant to evaluate the cold flow properties and exhaust gas emissions of diesel fuels

Zhicheng Zhao,Song Yan,Jun Lian,Wei Chang,Yuan Xue,Zhongyi He,Dongsu Bi,Sheng Han

In this paper, a new kind of nanohybrid poly(tetradecyl methyl-acrylate)-graphene oxide (PMA 14 -GO) as pour point depressant (PPD) was prepared from graphene oxide, using matrix via in situ free radical polymerization. The effect of PMA 14 -GO (i.e., PMA 14 -3GO, PMA 14 -6GO and PMA 14 -9GO) PPDs on the cold flow properties and exhaust gas emissions of diesel fuels were studied. Results indicated that PMA 14 -GO PPDs exhibited a better effect on cold filter plugging point (CFPP) and solidifying point (SP) than that of PMA 14 . Among them, PMA 14 -6GO and PMA 14 -9GO were the most suitable candidates for improving CFPP and SP. Specifically, upon addition of 0.2   wt% PMA 14 -6GO could reduce the CFPP of diesel by 14   °C, and 0.2   wt% PMA 14 -9GO reduced the SP of diesel by 19   °C. Moreover, PMA 14 -GO PPDs could effectively lower the low-temperature. Other fuel properties were also determined and compared with the ASTM D975 . Given the heterogeneous nucleation mechanism, uniform and tiny particle-shaped crystals were observed by polarizing optical microscopy and differential scanning calorimetry. In addition, burning diesel fuel with PMA 14 -GO PPDs effectively reduced HC and CO emissions, whereas NO and CO 2 emissions increased with the increased engine speed at full load.

Combined use of analyte protectants and precolumn backflushing for a robust, high-throughput quantitative determination of aroma compounds in cigarette mainstream smoke by gas chromatography-tandem mass spectrometry

Qiong Guo,Lining Pan,Yaqiong Qin,Fuwei Xie,Xiaoyu Wang,Xiaodong Zhao,Li Chen,Bing Wang,Junlan Cai,Huimin Liu

Trace analysis of multi-targets in complex matrices such as cigarette smoke has always been a great challenge for analysts. In this paper, a high-throughput qualitative and quantitative method was developed and validated to determine 559 aroma compounds in mainstream smoke using gas chromatography-tandem mass spectrometry. Among four commonly used extraction solvents, dichloromethane showed obvious advantages in extracting the target aroma compounds with different polarity. An analyte protectant mixture consisting of 3-methoxy-1,2-propanediol, 1,2-octandiol, 1,2-nonanediol, and 1,2-tetradecanediol was first presented to compensate for the matrix effect, which was suitable for solvents of a wide polarity range such as hexane, dichloromethane, acetone, acetonitrile, and methanol. Moreover, the introduction of precolumn backflushing markedly improved the instrument robustness in analyzing complex cigarette smoke. The results showed that the system retained good stability after 30 days of injection. The proposed method performed well in terms of key validation parameters: accuracy (70.3–118.8% for 552 compounds), inter/intraday precision (0.1–10.7% and 0.2–18.2%), and sensitivity (limit of detection 0.12–102.54 ng/mL). Finally, this method was successfully applied to analyze 12 different commercial cigarette brands. The proposed method has good application prospects based on its robustness and may be used as a potential tool to transfer the cigarette design from an experience-dependent mode to a digital design mode. This method also shows potential in assaying aroma compounds in essentials, food or plant-based substrates.