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- 摘要
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Rapid and sensitive detection of formaldehyde using portable 2-dimensional gas chromatography equipped with photoionization detectors
摘要： We developed an automated and highly portable device for rapid and sensitive formaldehyde detection based on heart-cutting 2-dimensional gas chromatography. In this design, the air sample was first absorbed by a preconcentrator before it is injected into the 1st-dimensional column (Rtx?-VMS). The partial elution from the 1st-dimensional column containing formaldehyde was re-injected into the 2nd-dimensional column (Rt? Q-BOND column) for further separation. The detection of formaldehyde was achieved by using a micro-helium dielectric barrier discharge photoionization detector that is able to ionize formaldehyde (ionization potential = 10.88 eV). Due to the use of many miniaturized components, the entire system has a weight of only 1.3 kg (excluding the helium cartridge) and dimensions of only 27 cm x 24 cm x 12 cm. It is capable of detecting formaldehyde down to 0.5 ppb (V/V) with a signal-to-noise ratio of 6 in only 11 min (including 6 min of sampling). Meanwhile, simultaneous separation and detection of other air pollution related toxic compounds, such as benzene, toluene, ethylbenzene, and xylene, was also demonstrated by the 1-dimensional column and a flow-through micro-photoionization detector. The device developed here should have a broad range of applications in environmental protection, industries, space exploration, and battlefield.
关键词： Gas chromatography,Air quality control,Indoor air analysis,Photoionization detector,2D GC,Formaldehyde detection
更新于2025-09-23 15:23:52
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EXPRESS: Analysis of Natural Gas Using a Portable Hollow-Core Photonic-Crystal-Coupled Raman Spectrometer
摘要： The low accessibility of natural gas fields and transporting pipelines requires portable online analyzers of the composition of natural gas, ensuring nearly chromatographic precision and capable of in situ analysis of a wide range of gases, including infrared-inactive ones (hydrogen, oxygen, nitrogen, chlorine). We have developed an express method of gas analysis meeting all requirements for the analysis of natural gas and its derivative mixtures using a portable 532 nm Raman spectrometer rigidly connected to a hollow-core crystal photonic fiber.
关键词： hollow-core photonic crystal fiber,HC-PCF,Raman spectrometry,gas chromatography,natural gas,calibration gas mixture
更新于2025-09-23 15:21:01
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[Environmental Chemistry for a Sustainable World] Nanosensors for Environmental Applications Volume 43 || Development of Optical Sensor Strips for Point-of-Care Testing for Pesticide
摘要： Disposable or point-of-care sensors are a promising tool for low-cost and rapid sensing of analytes including pesticides. They find important applications in pesticide-contaminated food, agro-products, and water quality monitoring. This chapter highlights the implication and significance of pesticide residue identification in foodstuffs and overviews the most frequently engaged analytical techniques, and finally their benefits and limitations are discussed. Disposable strip-based biosensors have their intrinsic advantages and some disadvantages, but their cost-effectiveness and portability have turned them as a potential possibility for point-of-care (POC) testing of various pesticides. The fabrication of robust, low-cost, reliable, and sensitive sensors with the aid of both simple naked eye-based and portable readout-based detectors is the driving factor in this sensor’s technology area. The pending limitations can be overcome by adapting new specific recognition elements and better signal generative particles or systems. The integration of these devices with card readers or smartphones can make them more user-friendly and will provide more accurate quantitative information.
关键词： Organophosphates,Pesticide,Immunoassay,Aptamer,Biosensors,Immunochromatographic assay,Point-of-care,Antibody,Rapid detection,Nanosensors,Gas chromatography
更新于2025-09-23 15:21:01
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A single light spot GC detector employing localized surface plasmon resonance of porous Au@SiO <sub/>2</sub> nanoparticle multilayer
摘要： This paper describes the synthesis of a nano-porous multilayered film consisting of Au@SiO2 nanoparticles. This film was used to miniaturize the size of a localized surface plasmon resonance (LSPR)-based capillary gas chromatograph (GC) detector. A layer-by-layer (LbL) approach with proper surface reaction sequences was used to create a multilayer structure that consisted of as many as five layers of Au@SiO2 nanoparticles. The center wavelength of LSPR was shifted from 520 to 634 nm due to the approximation of additional layers of nanoparticles. The vapor response time for this Au@SiO2 multilayer LSPR sensor was identical to that of an Au nanoparticle monolayer, which confirmed that this multilayer structure has a high level of gas permeability. The multilayer was synthesized inside a glass capillary for use as a GC detector. Due to the enhancement of absorbance, the gas chromatographic signal was obtained via a single spotlight that penetrated one side of the glass capillary and was then reflected by a silver mirror coated on the opposite side. The detection limits were ≤20 ng for cyclohexanone and m-xylene.
关键词： gas chromatography,localized surface plasmon resonance,multilayer film,miniaturization,Au@SiO2 nanoparticles,VOC detection
更新于2025-09-19 17:15:36
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Gas chromatography vs. quantum cascade laser-based??N <sub/>2</sub> O flux measurements using a novel chamber design
摘要： Recent advances in laser spectrometry offer new opportunities to investigate the soil–atmosphere exchange of nitrous oxide. During two field campaigns conducted at a grassland site and a willow field, we tested the performance of a quantum cascade laser (QCL) connected to a newly developed automated chamber system against a conventional gas chromatography (GC) approach using the same chambers plus an automated gas sampling unit with septum capped vials and subsequent laboratory GC analysis. Through its high precision and time resolution, data of the QCL system were used for quantifying the commonly observed nonlinearity in concentration changes during chamber deployment, making the calculation of exchange fluxes more accurate by the application of exponential models. As expected, the curvature values in the concentration increase was higher during long (60 min) chamber closure times and under high-flux conditions (FN2O > 150 μg N m?2 h?1) than those values that were found when chambers were closed for only 10 min and/or when fluxes were in a typical range of 2 to 50 μg N m?2 h?1. Extremely low standard errors of fluxes, i.e., from ～ 0.2 to 1.7 % of the flux value, were observed regardless of linear or exponential flux calculation when using QCL data. Thus, we recommend reducing chamber closure times to a maximum of 10 min when a fast-response analyzer is available and this type of chamber system is used to keep soil disturbance low and conditions around the chamber plot as natural as possible. Further, applying linear regression to a 3 min data window with rejecting the first 2 min after closure and a sampling time of every 5 s proved to be sufficient for robust flux determination while ensuring that standard errors of N2O fluxes were still on a relatively low level. Despite low signal-to-noise ratios, GC was still found to be a useful method to determine the mean the soil–atmosphere exchange of N2O on longer timescales during specific campaigns. Intriguingly, the consistency between GC and QCL-based campaign averages was better under low than under high N2O efflux conditions, although single flux values were highly scattered during the low efflux campaign. Furthermore, the QCL technology provides a useful tool to accurately investigate the highly debated topic of diurnal courses of N2O fluxes and its controlling factors. Our new chamber design protects the measurement spot from unintended shading and minimizes disturbance of throughfall, thereby complying with high quality requirements of long-term observation studies and research infrastructures.
关键词： gas chromatography,soil–atmosphere exchange,chamber design,nitrous oxide,quantum cascade laser,flux measurements
更新于2025-09-19 17:13:59
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Doping effects of ZnO quantum dots on the sensitive and selective detection of acetylene for dissolved-gas analysis applications of transformer oil
摘要： We report on the doping effect on the sensing properties of ZnO quantum dots (QDs) for the detection of acetylene. We found that In-doped ZnO (IZO) QDs exhibited a better sensing performance to 10 ppm acetylene than undoped ZnO (ZO) QDs and Al-doped ZnO (AZO) QDs. The higher sensing response of IZO QDs can be attributed to a greater number of reactive sites for detecting acetylene, which is likely to originate from the increased number of oxygen vacancies, and the larger optical band gap and surface area of IZO. This is due to a higher valence dopant and a smaller particle size. The sensing properties of IZO QDs to 10 ppm acetylene was also found to be superior to previously reported acetylene sensors that are based on semiconducting metal oxides. Furthermore, we demonstrated that 10 ppm of acetylene can be selectively detected in air within ～100 s using a recently developed miniaturized gas chromatography (GC) integrated with the IZO QDs sensor. In addition, we found that the device can detect the major fault gases of hydrogen and acetylene separately within ～100 s. Our study demonstrates that the device can be utilized in the GC-based on-line dissolved gas analysis to detect small amounts of acetylene gas in transformer oil.
关键词： Acetylene gas sensor,Dissolved gas analysis,Gas chromatography,Transformer oil,Quantum dots,ZnO
更新于2025-09-16 10:30:52
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Red‐Blood‐Cell Waveguide as a Living Biosensor and Micromotor
摘要： The changes of flavor components during boiling in Lentinus edodes were studied by high-performance liquid chromatography and gas chromatography-mass spectrometry in this article. Results showed that nonvolatile flavor components in L. edodes gradually transferred into the soup during boiling. Contents of nonvolatile flavor substances in the soup increased significantly (p < .05) compared with the preboiling period (15 minutes) and gradually maintained a balanced situation with the boiling time extended. During boiling, content of alcohols gradually reduced, especially the content of 1-octen-3-ol, which is a typical flavor component in L. edoedes. The contents of sulfur compounds, aldehydes, and hydrocarbons increased first and finally decreased gradually with the boiling time extended. Therefore, the changes of flavor components in the soup almost maintained a balanced situation with the boiling time from 30 to 60 minutes. The results of this article could provide a theoretical basis for the changes of flavor compounds in L. edodes during boiling.
关键词： flavor components,gas chromatography–mass spectrometry,High-performance liquid chromatography,boiling,Lentinus edodes
更新于2025-09-11 14:15:04
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7.3: Research on LCD display performance improvement based on mini‐LED backlight
摘要： The changes of flavor components during boiling in Lentinus edodes were studied by high-performance liquid chromatography and gas chromatography-mass spectrometry in this article. Results showed that nonvolatile flavor components in L. edodes gradually transferred into the soup during boiling. Contents of nonvolatile flavor substances in the soup increased significantly (p < .05) compared with the preboiling period (15 minutes) and gradually maintained a balanced situation with the boiling time extended. During boiling, content of alcohols gradually reduced, especially the content of 1-octen-3-ol, which is a typical flavor component in L. edoedes. The contents of sulfur compounds, aldehydes, and hydrocarbons increased first and finally decreased gradually with the boiling time extended. Therefore, the changes of flavor components in the soup almost maintained a balanced situation with the boiling time from 30 to 60 minutes. The results of this article could provide a theoretical basis for the changes of flavor compounds in L. edodes during boiling.
关键词： flavor components,gas chromatography–mass spectrometry,High-performance liquid chromatography,boiling,Lentinus edodes
更新于2025-09-11 14:15:04
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DLLME-GC/ECD Method for the Residual Analysis of Parathion-Methyl and its Application in the Study of the UV-Photodegradation Process
摘要： A new method has been developed to determine trace levels of organophosphorus pesticide parathion-methyl in water samples by using dispersive liquid-liquid microextraction (DLLME), followed by gas chromatograph coupled with electron capture detector (GC/ECD) analysis. The optimized and validated method showed high extraction recovery (101.1%), high enrichment factor (57.3), low limits of detection and quantification, 0.083 and 0.250 μg L-1, respectively. The established DLLME-GC/ECD method has been successfully applied for the evaluation of the photodegradation of the parathion-methyl by UV254nm radiation in different conditions of pH and temperature. The parathion-methyl photodegradation at pH 3 and 35 °C achieved > 99.5% after 120 min of exposition. For this condition, it was observed the kinetic rate of 0.0515 min-1, the quantum yield of 1.22 × 10-5 mol Einstein-1 and a half-life time of 13.46 min. All experimental conditions tested proved to be strongly influenced by pH and temperature. The application of the optimized process in distilled and drinking water spiked with parathion-methyl provided residues of this pesticide at levels below the maximum permitted by Brazilian legislation, which is 9.0 μg L-1.
关键词： UV radiation,degradation,gas chromatography,pesticide,dispersive liquid-liquid microextraction
更新于2025-09-11 14:15:04
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Synthesis, Characterization and Photocatalytic Efficiency of ZnO/MWCNT Nanocomposites Prepared Under Different Solvent Conditions
摘要： Here we report the application of zinc oxide (ZnO) coated multi-walled carbon nanotube (MWCNT) composites in the photocatalytic decomposition of acetaldehyde (AA). Zinc oxide nanoparticles were successfully coated on the multi-walled carbon nanotube via impregnation process using zinc acetate (Zn(CH3COO)2 × 2H2O) as precursor and sodium dodecyl sulfate (SDS) treated multi-walled carbon nanotube as raw material under different solvent conditions. The applied solvents during preparation were ethanol (EtOH) and water (H2O). As-prepared materials were characterized by thermal analysis (TG), X-ray diffraction (XRD), specific surface area measurement (BET) and transmission electron microscopy (TEM) techniques. Photocatalytic efficiencies of as-prepared composites were investigated in a stationary reactor equipped with UV lamp. Decomposition of acetaldehyde was followed by using gas chromatography (GC). Observations revealed that using impregnation method and different solvents the preparation of ZnO/MWCNT nanocomposites can be controlled easily. The highest degradation rate was achieved with the nanocomposite was synthetized using ethanol as solvent. The photocatalytic experiments revealed that the composite has higher photocatalytic activity than that of both the zinc oxide nanoparticles and the mechanical mixture of multi-walled carbon nanotube and zinc oxide.
关键词： Transmission Electron Microscopy,Zinc Oxide,Photocatalysis,Gas Chromatography,Nanocomposite
更新于2025-09-09 09:28:46