查找使用阿拉丁产品的科研文献

Sensitive determination of amphetamine-type stimulants in human hair by electro-enhanced solid-phase microextraction coupled to gas chromatography with nitrogen-phosphorus detector

Aiying SONG,Rong LIU,Xinghe HE,Linlin WEI

In the field of forensic sciences, the analysis of amphetamine-type stimulants in hair samples has become a fundamental tool for assessing long-term substance use. The persistent nature of amphetamine-type stimulants in hair provides a unique chronological record of drug intake, offering valuable insights for legal and clinical applications. Developing a simple, sensitive, and reliable method for the determination of these drugs in hair samples remains an important issue in forensic analysis. In this study, polydimethylsiloxane modified stainless steel fiber was firstly fabricated. By taking advantage of the affinity of the polydimethylsiloxane coating toward amphetamine-type stimulants and the excellent conductivity of stainless steel wire, an electro-enhanced solid-phase microextraction coupled with gas chromatography equipped with a nitrogen-phosphorus detector method was established to sensitively determine four common amphetamine-type stimulants in hair samples. The experimental results showed a linear range from 0.1 to 50 µg L⁻¹. The limits of detection and qualification respectively varied from 0.012 to 0.039 and 0.05 to 0.13 µg L⁻¹ ( S / N = 3), and it exhibited good reproducibility (< 6.2%). Recoveries ranging from 79% to 106%, with a relative standard deviation of < 6.7%, were obtained for all analytes. Fiber-to-fiber reproducibility (RSD), obtained using three fibers, was < 8.8%. The developed strategy combined the affinity of the polydimethylsiloxane coating towards amphetamine-type stimulants with the electrical conductivity of the stainless steel wire, effectively improving the enrichment ability and detection sensitivity, and achieving simultaneous selective enrichment and detection of several analytes. This is a simple, efficient, and reliable method for the analysis of amphetamine-type stimulants from complex matrices.

Oxygen Vacancies Enabled MOF-Derived Tb–SnO2 Compound for a High-Response, Low Detection Limit, and Humidity-Tolerant Chemiresistive Gas Sensor of Formaldehyde

Na Chu,Zhihua Wang,Fubo Gu

Tb-doped SnO2 (represented as Tb–SnO2) was prepared by calcining Tb-doped Sn MOF synthesized by a solvothermal method. 5% Tb–SnO2 exhibits excellent selectivity, high response (28.2), and fast response/recovery time (28 s/135 s) toward 50 ppb (volume concentration in parts per billion) formaldehyde (HCHO) at low operating temperature (200 °C). The low detection limit of the HCHO gas sensor is mainly due to the large number of oxygen vacancies in Tb–SnO2 caused by the charge imbalance between Tb ions and Sn ions during the high-temperature calcination process of Tb-doped Sn MOF. Oxygen vacancies promote the conversion of oxygen molecules into active adsorbed oxygen species, narrow the band gap of semiconductor oxides, and reduce the activation energy of formaldehyde gas-sensing reactions, thereby improving the performance of gas sensors. 5% Tb–SnO2 gas sensor has strong moisture resistance, with a response value of 209.3 to 10 ppm of HCHO at a high relative humidity of 80%. The moisture resistance mechanism of the material is explained as Tb3+/Tb4+ redox pairs acting as water molecule capture agents, which reduce the occupation of gas-sensing reaction active sites by water molecules on the material surface.

Room temperature g-C3N4/Mo1.33CTx-based enhanced acetone gas sensor by visible light excitation for highly responsive and rapidly recoverable diabetic breath detection

Chenxing Wang,Yinghao Xie,Yong Liu,Jing Wang,Shixiang Sun,Xiaoteng Jia,Qingrun Li,Liang Zhu,Fangmeng Liu,Geyu Lu

MXenes are characterized by high specific surface area and narrow band gap, while in-plan order MXene (i-MXene) provides enhanced ordered active sites through a vacancy structure, making it a promising 2D material for room temperature gas sensors. However, MXene-based gas sensors face challenges such as low response value, high limit of detection (LOD), poor recoverability, and long response/recovery time. Herein, we fabricated a room temperature gas sensor using g-C 3 N 4 /Mo 1.33 CT x sensing material and explored its sensing performance under visible light excitation. The visible light excitation brought a substantial enhancement in acetone sensing performance (328.8 % response in 2.5 ppm acetone), which was a 3.4-fold improvement compared with the dark scenarios. The LOD of the sensor was reduced to 50 ppb by visible light excitation, and the response/recovery time (15 s/34 s, in 2.5 ppm acetone) was drastically reduced with a high recovery level of > 97 %. Furthermore, mechanism exploration revealed that introducing g-C 3 N 4 material facilitates photogenerated carrier separation and increases gas adsorption sites, therefore achieving a higher gas response under light. This developed sensor achieved success in initial screening for diabetic ketoacidosis via breath analysis, thereby underscoring its potential for clinical diagnostic applications. This work contributes to explain the interaction of i-MXene with volatile organic compound molecules, and validates the prospect of i-MXene materials as sensitive materials for gas sensors.

Preparation and self-assembled behaviors of OPPEA and A-BPEF composite Langmuir-Blodgett films with photovoltaic conversion and acid-base gas sensing properties

Cuiru Wang,Xinyu Li,Wenhui Gu,Yisong Zhao,Tifeng Jiao

The composite Langmuir-Blodgett films of organic photovoltaic materials demonstrate unique advantages in the fields of photovoltaic devices, sensing, and chiral optics by fusing the functionality of organic materials with the orderliness of LB technology through precise assembly at the molecular scale. In this study, composite LB films of o-phenylphenoxyethyl acrylate (OPPEA) and bis-etherfluorene acrylate (A-BPEF) with Congo red (CR), methylene blue (MB), rhodamine B (RhB), and Saffron T (ST) dyes, respectively, have been successfully prepared by LB technology. The microstructure and optical properties of the composite films were systematically characterized by means of surface pressure-area isotherms (π-A curves), atomic force microscopy (AFM), transmission electron microscopy (TEM), contact angle measurements, and UV–visible spectroscopy, and the acid-base gas response and photoelectric conversion properties were investigated. The results show that different dye subphases significantly affect the molecular arrangement and microscopic morphology of the composite films, and the OPPEA/CR and A-BPEF/CR composite films exhibit significant response to HCl and NH 3 gases, while the OPPEA/RhB and A-BPEF/ST composite films show excellent photoelectric conversion efficiency and stability. This study provides a theoretical basis for the design and application of high-performance organic photovoltaic materials.

Elucidating the origin of cellulose in various fibers and textiles via gas chromatography coupled with high resolution mass spectrometry based on pyrolysis behavior

Tiefeng Xu,Xiangjie Meng,Gangqiang Wang,Wangyang Lu

The identification of cellulose fibers from different sources remains a significant challenge across various fields due to their complex structural composition and diverse applications. In this study, pyrolysis gas chromatography/high-resolution mass spectrometry (Py-GC/HRMS) was employed to identify cellulose fibers and fabrics utilizing a relative ratio approach based on pyrolyzate yield, with levoglucosan (LG) as the primary peak, furfural (FF) and 5-methyl-2(3H)-furanone (α-AL) as reference peaks. Initially, four cellulose fibers had large discrepancies in pyrolyzate yield relative ratios when pyrolyzed at 600°C. The FF to LG ratios were 0.58-0.83 for cotton, 0.25-0.35 for flax, 0.14-0.18 for viscose, and 0.05-0.07 for tencel, while the α-AL to LG ratios were 0.64-0.88 for cotton, 0.29-0.38 for flax, 0.18-0.22 for viscose, and 0.03-0.05 for tencel. The relative proportion of fabrics has significantly decreased compared to fibers, which indicated that the manufacturing process affected the fiber components. It confirmed that alkaline bleaching can effectively eliminate fiber impurities and enhance cellulose content, which contribute to the increase of LG yield and the decrease of relative ratio. This work marks the inaugural differentiation of four cellulose fibers and fabrics using Py-GC/HRMS, offering a valuable methodology and pivotal reference data for future investigations in the field.

N-doped carbon sphere-SiO2 composite structure materials with high adsorption rate and low regeneration energy consumption for CO2 capture from flue gas

Lin Qiao,Dong Fu

N-doped carbon-silicon composite adsorbent (NC@SiO 2 ) has garnered significant attention in the field of CO 2 capture. In this study, a novel NC@SiO 2 has been developed by combining hydrothermal synthesis, Stober method, and one-step carbonization activation. It exhibits a moderate static adsorption capacity (3 mmol/g, 298.15 K) , along with low adsorption heat (14.65–21.93 KJ/mol). At 313.15 K, the dynamic adsorption capacity and adsorption rate for CO 2 (volCO 2 : volN 2 = 15 %:85 %) are 2 mmol/g and 0.202 mmol/g/min, respectively. Additionally, it demonstrates excellent cycle stability, with the adsorption capacity decreasing by only 7 % after 10 cycles. Density Functional Theory (DFT) calculations confirm that the presence of functional groups of N and O significantly enhances CO 2 adsorption performance of NC@SiO 2 . The synergistic effect of SiO 2 coating, N doping, and K 2 CO 3 activation is important for improving CO 2 dynamic adsorption performance, positioning NC@SiO 2 as a promising candidate for capturing CO 2 from flue gas.

Multi-walled carbon nanotubes/polyaniline on the ethylenediamine modified polyethylene terephthalate fibers for a flexible room temperature ammonia gas sensor with high responses

Jiangwei Ma,Huiqing Fan,Zhexin Li,Yuxin Jia,Arun Kumar Yadav,Guangzhi Dong,Weijia Wang,Wenqiang Dong,Shuren Wang

The flexible room-temperature gas sensors are highly desirable to apply in wearable and portable equipment owing to their wearability. The research mainly focuses on the gas-sensing materials and few studies paid attention to the conjunction between flexible substrates and sensing materials. In this work, the polyethylene terephthalate (PET) fibers substrate is modified by ethylenediamine (EDA) to expose the amino group on the surface (PET-NH 2 ). This method is simple, cost-efficient, and easy to operate. The positively charged amino group could interact with negatively charged carboxyl (−COOH) of multi-walled carbon nanotubes (MWCNTs) by electrostatic attraction. The EDA treatment on PET effectively strengthens the connection between the flexible PET substrate and gas sensing materials with carboxyl as evidenced by SEM images. After the in situ polymerization process, the polyaniline (PANI) is successfully decorated on the MWCNTs. The fabricated PET-NH 2 -MWCNTs/PANI sensor exhibits strongly enhanced ammonia (NH 3 ) sensing performance as compared to the PET-MWCNTs/PANI sensor without the EDA treatment. The results suggest that the EDA treatment is an effective method to conjunct between flexible substrates and sensing materials, which shows great potential in the field of flexible gas sensors.

Aroma effects of critical volatile compounds during thermophilic bacteria pile-fermentation in dark tea using gas chromatography mass spectrometry and odor activity value

ZHU Wen,FANG Xin,WANG Wenfeng,XU Wencan,CHEN Wenjun,WU Shuang,HUANG Youyi,WANG Shengpeng

Thermophilic bacteria play an important role in aroma formation during pile-fermentation process of dark tea. With the aim to reveal the impact of thermophilic bacteria on volatile compounds in dark tea, Bacillus licheniformis (thermophilic bacteria) were inoculated into sun-dried green tea for spontaneous fermentation. In this study, headspace solid phase microextraction combined to gas chromatography mass spectrometry (HS-SPME-GC-MS), odor activity value (OAV), principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) were employed to investigated the characteristics of volatile compounds during thermophilic bacteria pile-fermentation. According to HS-SPME-GC-MS, a total of 64 volatile compounds were identified. PCA revealed that tea samples could be clearly discriminated from each other. Furthermore, sulcatone, hexanoic acid, linalool, 2-methyl-trans-decalin, myrtenal, and α-ionone were found to play an important role in discrimination of tea samples, based on OPLS-DA. In addition, the OAV could effectively characterize the aroma contribution of volatile compounds during thermophilic bacteria pile-fermentation, and (Z)-linalool oxide (furanoid), α-ionone, (E)-2-nonenal, and linalool were the critical volatile compounds of aroma quality in dark tea. This study provides insight into volatile compounds characteristics during thermophilic bacteria pile-fermentation in dark tea.

Gas Chromatography-Mass Spectrometric Analysis of Nematicidal Essential Oil ofValeriana amurensis P Smirn ex Kom (Valerianaceae) Roots and its Activity against Heterodera avenae

YC Li,H Ji,HT Li

Enhancing Selective Adsorption in a Robust Pillared-Layer Metal–Organic Framework via Channel Methylation for the Recovery of C2–C3 from Natural Gas

Yufang Wu,Zewei Liu,Junjie Peng,Xun Wang,Xin Zhou,Zhong Li

Here, we reported a strategy for channel methylation to construct a robust ultramicroporous metal–organic framework (MOF) Ni(TMBDC)(DABCO)0.5 through hydrothermal synthesis method and investigated its adsorption performance for recovering ethane (C2) and propane (C3) from natural gas. The as-synthesized Ni(TMBDC)(DABCO)0.5 featured ultramicroporosity with a uniform pore size of 0.5 nm. The resulting sample showed a strong adsorption interaction with C3H8 and C2H6, and its C3H8 adsorption capacity at a low pressure of 1 kPa was up to 2.80 mmol/g and its C2H6 adsorption capacity at a low pressure of 10 kPa reached as high as 2.93 mmol/g, exhibiting strong binding affinity for ethane and propane. The enhanced adsorption can be attributed to the presence of the dense and accessible methyl and methylene groups in the channels of the sample. Grand Canonical Monte Carlo (GCMC) simulations also confirmed that the methylene groups from the DABCO pillar and the methyl groups from the TMBDC ligand play an important role in enhancing the adsorption of ethane and propane. Its ideal adsorbed solution theory (IAST)-predicted selectivity of C2H6/CH4 reached unprecedentedly 29, much higher than most of the reported data for MOFs. The stability test confirmed that the crystal structure of Ni(TMBDC)(DABCO)0.5 still remained intact after it was exposed to moist air with a relative humidity of 100% for days. The breakthrough experiment demonstrated that the CH4/C2H6/C3H8 ternary mixture was completely separated using a fixed bed of Ni(TMBDC)(DABCO)0.5 at ambient temperature, showing a great potential for recovering the low content of ethane and propane from natural gas.

Dispersive microextraction based on water-coated Fe3O4 followed by gas chromatography–mass spectrometry for determination of 3-monochloropropane-1,2-diol in edible oils

Qin Zhao,Fang Wei,Neng Xiao,Qiong-Wei Yu,Bi-Feng Yuan,Yu-Qi Feng

In the present work, we developed a novel dispersive microextraction technique by combining the advantages of liquid-phase microextraction (LPME) and magnetic solid-phase extraction (MSPE). In this method, trace amount of water directly absorbed on bare Fe 3 O 4 to form water-coated Fe 3 O 4 (W-Fe 3 O 4 ) and rapid extraction can be achieved while W-Fe 3 O 4 dispersed in the sample solution. The analyte adsorbed W-Fe 3 O 4 can be easily collected and isolated from sample solution by application of a magnet. It was worth noting that in the proposed method water was used as extractant and Fe 3 O 4 served as the supporter and retriever of water. The performance of the method was evaluated by extraction of 3-monochloropropane-1,2-diol (3-MCPD) from edible oils. The extracted 3-MCPD was then derived by a silylanization reagent (1-trimethylsilylimidazole) before gas chromatography–mass spectrometry (GC–MS) analysis. Several parameters that affected the extraction and derivatization efficiency were investigated. Our results showed that the limit of detection for 3-MCPD was 1.1   ng/g. The recoveries in spiked oil samples were in the range of 70.0–104.9% with the RSDs less than 5.6% (intra-day) and 6.4% (inter-day). Taken together, the simple, rapid and cost-effective method developed in current study, offers a potential application for the extraction and preconcentration of hydrophilic analytes from complex fatty samples.

Rapid detection of Aspergillus spp. infection levels on milled rice by headspace-gas chromatography ion-mobility spectrometry (HS-GC-IMS) and E-nose

Shuang Gu,Wei Chen,Zhenhe Wang,Jun Wang,Yujia Huo

This study described the rapid detection of milled rice infected with Aspergillus spp. species based on headspace-gas chromatography ion-mobility spectrometry (HS-GC-IMS) and electronic nose (E-nose) combined with chemometrics, namely principal component analysis (PCA), k-nearest neighbor (kNN) and partial least squares regression (PLSR). 3D HS-GC-IMS imaging and their response differences enabled the discrimination among fungal species. kNN was used to differentiate rice samples with cdifferent levels of fungal infection and achieved correct classified rate of 94.44% and 91.67% by HS-GC-IMS and E-nose, respectively. PLSR method was used for quantitative regression of fungal colony counts in rice samples and good prediction performances were achieved by HS-GC-IMS (R p 2  = 0.909, RMSEP = 0.202) and E-nose (R p 2  = 0.864, RMSEP = 0.235). The results indicated that both HS-GC-IMS and E-nose approaches can potentially be implemented for the detection of fungal contamination levels in milled rice, and HS-GC-IMS fingerprinting coupled with chemometrics might be used as an alternative tool for a highly sensitive method. This research might provide scientific information on the rapid, non-destructive, and effective fungal detection system for rice grains .