• A new mechanism for the oxidation, and autoignition of 3-pentanol is proposed. • New experimental Rapid Compression Machine data, including speciation, is reported. • The model includes a set of new ab initio calculated reaction rate coefficients. • The model is validated on existing data in all temperature regimes of combustion. • This work is extended to blends with hydrogen, in the context of decarbonization. Reducing emissions in the transportation sector has highlighted the potential of oxygenates as alternative fuels, known for lowering soot emissions. Blending these alcohols with hydrogen, a carbon-free fuel, offers further potential for reducing carbon-based emissions. Because the description of the low-temperature combustion pathways of C 5 alcohols still needs to be improved, this study investigates the ignition delay times (IDTs) and mole fraction profiles of intermediates of 3-pentanol/hydrogen mixtures using a rapid compression machine over a low-to-intermediate temperature range. Experiments were also conducted for 3-pentanol/H 2 blends with mixing ratios of 100/0, 75/25, and 50/50 at pressures of 10, 15, and 20 bar, and equivalence ratios of 1.0 and 0.5. Gas chromatography, flame ionization detection, thermal conductivity detection, and mass spectrometry were employed for the quantification of the intermediates. These results therefore provide a rare detailed database for the validation of 3-pentanol kinetic models at high-pressure, low-temperature combustion conditions. Furthermore, ab initio calculations were performed to determine β-scission and isomerization reaction rates, supporting the development of a novel kinetic sub-mechanism for 3-pentanol, which shows better or equivalent agreement that previous works on the hereby-reported or existing literature data. This mechanism highlights the importance of the branching ratio of the initial H-abstraction step in the prediction of the IDTs as well as the importance of the 3-pentanone relevant pathways. It was used to evaluate the impact of hydrogen addition on 3-pentanol IDTs, revealing the importance of H 2 as a sink for hydroxyl radicals, readily converting them to H atoms then hydroperoxyl radicals.

Hydrogen production via aqueous ammonia electrolysis: electrolyte optimization, product selectivity, and efficiency analysis

Efficient analysis of sodium chromate by combining phase-transfer headspace strategy and GC-TCD.

Accelerated global economic growth and the accompanying rise in living standards increasingly rely on exploiting fossil fuels. However, the growing consumption of limited fossil energy sources and other petrochemicals has significantly intensified the deterioration of the environmental conditions. The CO2 gas released from burning hydrocarbon fuels may disrupt its balance in the environment, leading to widespread greenhouse effects like extreme weather conditions, global warming, rising sea levels, etc. The state-of-art electrochemical processes like electrochemical CO2 reduction reaction (CO2RR), have attracted growing attention, recently, to decrease the level of CO2 gas in the atmosphere by converting the CO2 to value-added hydrocarbons and thereby closing the carbon cycle. Despite its potential, CO₂ reduction reaction (CO₂RR) faces several challenges, including poor selectivity, low energy efficiency, and insufficient catalyst stability, which hinder its industrial scalability. To overcome these issues, recent studies have emphasized the development of advanced electrocatalysts to enhance both the efficiency and selectivity of CO₂ conversion. Recently, there have been significant efforts to find highly active and selective electrode materials to improve their overall performance in CO2-reduction reaction.In the current study, transition metal chalcogenides have been employed as promising electrocatalysts for CO2 reduction reaction. In this context, tin telluride (SnTe) nanoparticles were synthesized through a hydrothermal process, and their physicochemical properties were investigated by a variety of characterization techniques, including as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy.The electrocatalytic performance of SnTe nanoparticles for CO₂ reduction reaction (CO₂RR) was examined by different electrochemical experiments including cyclic voltammetry (CV), Linear sweep voltammetry (LSV), Tafel plots, and Chronoamerometry techniques. The electrochemical tests were performed in a conventional H-cell at ambient temperature, in which Nafion-117 proton exchange membrane was used to separate the anolyte solution (1M KOH) and CO2 saturated catholyte solution (0.3M NaHCO3). Gaseous products were analyzed using a gas chromatography apparatus equipped with a thermal conductivity detector (GC-TCD), and nuclear magnetic resonance (H-NMR) spectroscopy was employed to assess liquid products.The successful synthesis of SnTe nanoparticles was confirmed by XRD data, as reported in Figure 1a. The NMR spectra of the catholyte solution after a 2h chronoamperometry experiment at different applied potentials have been illustrated in Figure 1b. In NMR spectra, the peak presented at 8.36 ppm is attributed to formic acid. From the NMR spectra given in Figure 1b, the concentration of formic acid produced after 2 hours rises steadily at increasing applied potentials, showing a strong potential-dependent increase in the catalytic activity towards the production of formic acid. Notably, the NMR spectra reveal that formic acid is the only liquid product on SnTe nanoparticles at all applied potentials. Such a high product purity is crucial for the commercialization of electrocatalytic CO2RR as a promising technology. To investigate the durability of SnTe electrocatalysts, the catalytic performance of the synthesized nanoparticles in electrochemical CO2 reduction reaction (CO2RR) was evaluated through a long-term chronoamperometry experiment at -1.2V vs. RHE. Notably, a consistently stable current was observed throughout the stability test. In addition, the NMR data showed formic acid yield as the sole liquid product after continuous operation for several hours, indicating the excellent maintenance of electrocatalytic activity by the SnTe electrocatalysts. This observation was also confirmed by XPS and XRD data, where there was almost no change in the surface composition of SnTe nanoparticles after long-term operations.The results reported in the current research highlight the great potential of transition metal chalcogenides, namely tin telluride (SnTe), as highly selective electrocatalysts for converting CO2 into value-added hydrocarbons. Figure 1

Hydrofluorocarbon (HFC) regulations have prompted the development of technology, such as extractive distillation using ionic liquids, to separate reclaimed HFC-based refrigerant blends to recover lower Global Warming Potential (GWP) HFCs and repurpose high-GWP HFCs. Multicomponent mixtures, across the entire composition range in reclaimed refrigerants, need to be accurately quantified. Industrial standards on purity (i.e., 99.5 % by weight) are required for future reuse in next-generation refrigerant blends and repurposing HFCs that will be phased out. The present study investigates gas chromatography (GC) methods for analyzing multicomponent refrigerant mixtures R-404A, R-407C, R-410A, R-507, and R-513A. A low-cost GC with a thermal conductivity detector (TCD), various columns, and a sampling injection valve are used to quantify, single refrigerant components difluoromethane (HFC-32), pentafluoroethane (HFC-125), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1,-trifluoroethane (HFC-143a), and the hydrofluoroolefin, 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf). The effect of different columns, oven temperature, and carrier gas flow rate was investigated. A rigorous error analysis was performed on the method to determine measurement uncertainties. Results from the proposed method (HayeSep D column) show shorter to similar retention times than traditional methods (Carbopack B column), with standard deviations <0.64 % by weight and 95 % confidence level error of ±0.08 to ±0.8 wt% for all refrigerant mixtures. Shorter analysis time, lower GC operating temperatures, and less expensive supplies (e.g., GC column) are advantages of the proposed methodology. The study provides additional analytical understanding for researchers and the refrigerant manufacturing and reclamation industries. • HayeSep D provides shorter or similar retention times compared to Carbopack B for R-404A, R-407C, R-410A, R-507, and R-513A. • Calibration curves were prepared for HFC-32, HFC-125, HFC-134a, HFC-143a, and HFO-1234yf using a TCD and a sampling valve. • The study provides refrigerant reclaimers with an alternative option for analyzing refrigerant mixtures.

Abstract Rice husk gasification offers a sustainable route to produce hydrogen-rich biogas, addressing global energy security and environmental challenges. This study investigates the gasification of rice husk biomass in a horizontal tube furnace at 800°C under controlled nitrogen flow to optimize hydrogen production. The rice husk feedstock had a moisture content of 11.7%, ash content of 16.3%, volatile matter of 58.0%, fixed carbon of 13.9%, and a gross calorific value of 3411 kcal/kg. Biogas composition was analysed using gas chromatography with a thermal conductivity detector (GC-TCD), and it revealed a maximum hydrogen content of 50.99%. Compared to subsequent samples, it represents a 1.5 time increase in hydrogen yield. The study highlights rice husk as a viable biomass feedstock for renewable hydrogen production. Therefore, future work needs to focus on catalytic gasification through the use of nickel-based catalysts and biological pre-treatments like white-rot fungi degradation to enhance hydrogen yield and process efficiency. Conclusively, the research contributes to the advancement of renewable energy technologies with potential environmental benefits over fossil fuels and other biomass sources.

Optimization of quantitative analysis method for carboxyhemoglobin in severely decomposed spleen tissue influenced by a reducing agent.

Abstract. In the context of field thermal conductivity detector (TCD)-based gas chromatography (GC), we investigate a method to improve the system's specificity. The ratio of signals of two TCDs biased at two different voltages is calculated, allowing us to be independent of the analyte concentration and to exploit the fact that the thermal conductivity of any gaseous species varies uniquely with temperature. However, theoretical predictions as well as experiments indicate that this method helps peak identification only if the local analyte concentrations are far (2 to 3 orders of magnitude) beyond the typical concentrations encountered by portable trace analyzers.

As fossil fuels have finite resources and environmental drawbacks, there’s a growing interest in cleaner, renewable energy. Hydrogen (H2) is seen as a promising alternative to petroleum due to its non-toxic, clean combustion that only produces water and avoids carbon dioxide emissions. In this study, different ratios of ZnFe2O4–CeO2 nanopowder were synthesized via the glycine nitrate process (GNP). The ZnFe2O4–CeO2 nanopowder catalyst was prepared by GNP, which was immensely porous and had a cotton-like structure. Moreover, the glycine nitrate process, which is a synthesis technology, can offer the advantages of low cost, simplicity, and speed and create a porous structure for the catalyst. The BET measurement revealed that the specific surface area of the as-combusted ZnFe2O4–CeO2 nanopowder varied from 8.48 m2/g to 19.82 m2/g. Hydrogen production through the SRM process was monitored by using a gas chromatograph equipped with a thermal conductivity detector. The 20ZnFe2O4–80CeO2 powder had the highest H2 production without activation, reaching 7566.08 mL STP min–1 g-cat–1 at a reaction temperature of 550 °C achieved at an N2 flow rate of 30 sccm. This study indicates that the glycine nitrate process imparts a porous structure to the catalyst, thereby increasing hydrogen production. Moreover, suitable incorporation of CeO2 could improve the catalytic performance in the SRM process on hydrogen. Therefore, ZnFe2O4–CeO2 nanopowders may have significant economic prospects.

Abstract. We present a novel thermal conductivity detector (TCD) for gas sensing and gas chromatography. Its original architecture is based on a suspended membrane on top of which a heating element made of titanium nitride and a separated sensing element made of amorphous silicon are deposited. These sensors are micro-fabricated from 200 mm silicon wafers and tested on a gas bench. When used as a standalone gas sensor, they reach a theoretical detection limit (3σ) of 13 ppm for carbon dioxide in the air and exhibit a signal-to-noise ratio 4 times higher than that of conventional platinum TCDs.

Analyzing carbon monoxide concentration within an individual is crucial. The analysis of CO content in a tissue sample is performed using gas chromatography. The concentration is calculated based on a linear equation derived from the calibration curve created with the CO-fortified sample. However, when methemoglobin (MetHb) is formed from putrefaction, it inhibits CO binding to the sample and may lead to inaccurate results. MetHb results from the iron oxidation of normal heme hemoglobin (HHb), and by treating the sample with a reducing agent, it can be converted back to HHb. To investigate the effect of the reducing agent on spleen CO analysis, each sample was divided into two parts. One was treated with a 0.574 M sodium dithionite solution (Na2S2O4), a reduced sample, and the other was treated with a rinse solution, serving as the control sample, with both undergoing the same preparation process and analyzed using Gas Chromatography with a Thermal Conductivity Detector (GC-TCD). Spleen samples from 60 autopsy cases were analyzed. The results indicated that 48 cases showed lower CO levels when the sample was reduced compared to the control sample, where the difference of the control and reduced samples ranged from 2.21 to 93.24%, with a median value of 13.83%. 12 cases exhibited no difference, where the difference between control and reduced sample ranged from 0.05 to 1.57%, with a median value of 0.67%. Our findings demonstrate that MetHb formed during decomposition can significantly inhibit CO binding in spleen tissue, leading to overestimation of CO levels when no reducing agent is used. Therefore, incorporating sodium dithionite treatment into GC-TCD methods improves the accuracy of postmortem CO quantification, particularly in putrefied samples.

A method for determining citrate content in specialty paper using headspace gas chromatography (HS-GC) is proposed. This method is based on the reaction between sodium citrate and potassium permanganate under acidic conditions, which generates CO2. The CO2 is detected by a thermal conductivity detector and the sodium citrate content is calculated using a standard curve. Optimization of the method was conducted by investigating various parameters, including gas chromatography conditions, equilibrium time, equilibrium temperature, and injection volume. The method's accuracy and precision were assessed through method validation. The results demonstrated that the relative standard deviation (RSD) was ≤3.00%, and the recovery rate ranged from 91% to 102%, indicating good reliability and accuracy. This method is simple, rapid, and precise, making it an effective approach for the determination of citrate content in specialty paper.

Hydrogen embrittlement (HE) is a critical concern in advanced high-strength steels (AHSS), particularly after resistance spot welding (RSW) and laser welding (LW), where localized microstructural changes and residual stresses exacerbate susceptibility to hydrogen-induced cracking. This review comprehensively examines the hydrogen embrittlement susceptibility of RSW and LW joints by analyzing key influencing factors such as hydrogen diffusion, trapping sites, and microstructural transformations at the weld and heat-affected zones (HAZ). The study discusses various hydrogen charging methods, including acid immersion and cathodic charging, to simulate real-world hydrogen exposure conditions. To evaluate hydrogen embrittlement susceptibility, a range of mechanical and electrochemical testing techniques are reviewed. For RSW joints, methods such as slow strain rate tensile testing (SSRT), incremental load testing (ILT), and constant load testing (CLT) are explored to assess delayed fracture risks. Additionally, for LW joints, self-restraint bead-on-plate tests are examined, highlighting the role of weld pool dynamics and solidification characteristics in hydrogen trapping. Furthermore, advanced hydrogen quantification techniques, including thermal desorption spectroscopy (TDS) and gas chromatography with a thermal conductivity detector, are discussed to accurately determine hydrogen concentration and distribution in welded regions. By correlating hydrogen uptake, microstructural evolution, and embrittlement susceptibility, this review provides a systematic understanding of hydrogen embrittlement mechanisms in RSW and LW joints. The insights presented aim to support the development of optimized welding strategies and mitigation approaches, enhancing the structural reliability of AHSS for automotive and industrial applications.

The widespread presence of pesticides-especially malathion-in aquatic environments presents a major obstacle to conventional remediation strategies, while the ongoing global energy crisis underscores the urgency of developing renewable energy sources such as hydrogen. In this context, photocatalytic water splitting emerges as a promising approach, though its practical application remains limited by poor charge carrier dynamics and insufficient visible-light utilization. Herein, we report the design and evaluation of a series of TiO2-based ternary nanocomposites comprising commercial P25 TiO2, reduced graphene oxide (rGO), and molybdenum disulfide (MoS2), with MoS2 loadings ranging from 1% to 10% by weight. The photocatalysts were fabricated via a two-step method: hydrothermal integration of rGO into P25 followed by solution-phase self-assembly of exfoliated MoS2 nanosheets. The composites were systematically characterized using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity was assessed through two key applications: the degradation of malathion (20 mg/L) under simulated solar irradiation and hydrogen evolution from water in the presence of sacrificial agents. Quantification was performed using UV-Vis spectroscopy, gas chromatography-mass spectrometry (GC-MS), and thermal conductivity detection (GC-TCD). Results showed that the integration of rGO significantly enhanced surface area and charge mobility, while MoS2 served as an effective co-catalyst, promoting interfacial charge separation and acting as an active site for hydrogen evolution. Nearly complete malathion degradation (~100%) was achieved within two hours, and hydrogen production reached up to 6000 µmol g-1 h-1 under optimal MoS2 loading. Notably, photocatalytic performance declined with higher MoS2 content due to recombination effects. Overall, this work demonstrates the synergistic enhancement provided by rGO and MoS2 in a stable P25-based system and underscores the viability of such ternary nanocomposites for addressing both environmental remediation and sustainable energy conversion challenges.

An underwater gas chromatograph for in-situ analysis of organics in deep-sea.

This study reports the development of a novel analytical method for the determination of carbon dioxide (CO2) along with the other main greenhouse gases (GHG)‒methane (CH4) and nitrous oxide (N2O)‒ from environmental samples by gas chromatography (GC) using an electron capture detector (ECD). This new method was compared and validated with the standard GC method for the determination of CO2 using a thermal conductivity detector (TCD). The main performance parameters considered for the validation of an analytical method were evaluated: selectivity/specificity, linearity/working range, precision, trueness, limit of detection (LOD) and limit of quantitation (LOQ). This comparison was carried out using gas standards, reference materials and environmental samples containing GHG. Both the ECD- and TCD-based chromatographic analytical methods displayed a similar precision (3.1-3.4 %) and accuracy (101-106 %) for CO2 analysis. Although the LOQ for the ECD detector is higher than that of the TCD detector (300 vs. 99 µmol mol⁻¹), it is still sufficient for the analysis of most GHG samples. Once validated, the new analytical method was used for the simultaneous determination of CO2, CH4 and N2O in gaseous samples obtained from a wide range of conditions and agricultural environments. To this end, a GC instrument was equipped with a flame ionization detector (FID) for the determination of CH4 and an ECD for CO2 and N2O, connected in series by a system of valves. In this way, it was possible to accurately measure the main GHG present in the atmosphere and in gaseous samples, simplifying the required laboratory equipment and reducing the associated labor and costs.

Abstract. This article presents a simple method for determining greenhouse gases (CH4, CO2 and N2O) using an alternative new set-up of the chromatographic system. The novelty of the presented method is the application of a Carboxen 1010 PLOT capillary column for separation of trace gases – CH4, CO2 and N2O – from air samples and their detection using a barrier discharge ionisation detector (BID). Simultaneously, a parallel molecular sieve column RT-Msieve 5A connected to a thermal conductivity detector (TCD) allowed the determination of CH4, N2 and O2 concentrations from 0.2 % to 100 %. The system was equipped with an autosampler transferring the samples without air contamination thanks to a vacuum pump and inert gas flushing. Method validation was performed using commercial gas standards and comparative measurement of CO2, CH4 and N2O concentrations applying cavity ring-down spectroscopy (CRDS). A 3 d continuous measurement series of greenhouse gas (GHG) concentrations in ambient air and tests of typical vial sample measurements with increased GHG concentrations were performed. The advantage of this method is that the system is easy to set up and allows for simultaneous detection and analysis of the main GHGs using one gas chromatography (GC) column and one detector, thereby omitting the need for an electron capture detector (ECD) containing radiogenic components for N2O analysis and a flame ionisation detector (FID) with a methaniser for low-concentration CO2 samples. The simplification of the system reduces analytical costs, facilitates instrument maintenance and improves measurement robustness.

This article presents advancements in using Micro-Electro-Mechanical Systemsbased (MEMS-based) devices for measuring the calorific value and hydrogen content in hydrogenated gaseous fuels, such as natural gas. As hydrogen emerges as a pivotal clean energy source, blending it with natural gas becomes essential for a sustainable energy transition. However, precise monitoring of hydrogen concentrations in gas distribution networks is crucial to ensure safety and reliability. Traditional methods like gas chromatography and mass spectrometry, while accurate, are often too complex and costly for real-time applications. In contrast, MEMS technology offers innovative, cost-effective alternatives that exhibit miniaturization, ease of installation, and rapid measurement capabilities. The article discusses the development of a novel MEMS thermal conductivity detector (TCD) and a new ionization spectrometer with an optical readout, both of which enable accurate assessment of hydrogen content and calorific values in natural gas. The TCD has demonstrated a 3% uncertainty in calorific value measurement and an impressive accuracy in determining hydrogen concentrations ranging from 2% to 25%. The research detailed in this article highlights the feasibility of integrating these MEMS devices into existing infrastructure, paving the way for efficient hydrogen monitoring in real-world applications. Moreover, preliminary findings reveal the potential for robust online process control, positioning MEMS technology as a transformative solution in the future of energy measurement. The ongoing innovations could significantly impact residential heating, industrial processes, and broader energy management strategies, facilitating a sustainable transition to hydrogen-enriched energy systems.

ABSTRACTThis paper presents a new method for fast simultaneous monitoring of individual gas concentrations in a gas mixture by using small micromachined sensors. The developed method uses output data from multiple micromachined thermal conductivity detectors of different sensitivities. We confirmed that the fabricated sensors can accurately determine the concentrations of each of three gases in a mixture. The prototype sensor module was miniaturized to less than 1/72th the size of conventional gas chromatography (GC) equipment. Demonstration tests were conducted in a CO2 electrolysis cell for CO2 capture and utilization technologies, and each gas concentration was successfully monitored 176 times faster than conventional GC could for a mixture of H2, CO2, and CO gases.

Abstract This research examines how different flow regimes transient, and turbulent affect the electrical and optical properties and Hydrogen production of Bi reforming of methane (CO2/CH4/H2O) in a rotating gliding arc (RGA) reactor. The f arc parameter was measured using a high-speed camera and Fast Fourier Transform voltage analysis. Optical Emission Spectroscopy captured the RGA’s visible emission spectrum, while the rotational temperature was determined via C2 Swan band analysis using SPECAIR. Gas Chromatography with thermal conductivity detector and flame Ionization Detector determined the product gas composition. Different operating parameters, including the RGA swirl hole diameter (1 mm), steam to carbon (S/C) ratios (0.33 and 0.66), and flow rates varying from 6.7 to 40 SLPM, were tested to improve H2 and CO production. At 6.7 SLPM with S/C0.33, maximum H2 and CO production was 3.4% and 4.2% while at 8 SLPM with S/C0.66 maximum H2 and CO production was 3.9% and 5%. Increasing Q to 37.5 SLPM with S/C0.33 reduced H2 and CO production to 0.7%, and 1.7% while at 40 SLPM and S/C0.66, H2 and CO production reduced to 0.8% and 2.0%, due to lower residence time. These findings are essential for scaling up and optimizing the RGA reactor for H2 production.