To see the other types of publications on this topic, follow the link: Total oxidation of methanol.
Journal articles on the topic 'Total oxidation of methanol'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Total oxidation of methanol.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Zhang, Jie, Shu Zhong Wang, Yan Meng Gong, Yan Hui Li, and Jia Ming Lu. "Co-Oxidation Effects of Methanol on Reactive Orange 7 and Polyvinyl Alcohol in Supercritical Water." Advanced Materials Research 788 (September 2013): 258–62. http://dx.doi.org/10.4028/www.scientific.net/amr.788.258.
Full textAbstract:
Methanol acting as co-oxidation component was introduced in supercritical water oxidation experiments of Reactive Orange 7 and polyvinyl alcohol. Experiments were performed at 673K and 25MPa. The concentrations of Reactive Orange 7 and polyvinyl alcohol were constant at 5wt% and 1wt%, respectively, with increasing methanol concentrations. For the binary mixture of methanol/ Reactive Orange 7, the experiment results showed that the total nitrogen and total organic carbon removals in the mixture were higher than that in the absence of methanol, and as methanol concentration increased, the accelerating effect was more notable. For methanol/polyvinyl alcohol mixture experiment, at the oxidation coefficient of 2.0, the presence of methanol (0.2-1.5 wt%) accelerated the decomposition rates of polyvinyl alcohol and total organic carbon, while methanol addition showed negative effects at the oxidation coefficient of 1.05. The inhibition reaction was attributed to the increment in induction time of polyvinyl alcohol oxidation in the presence of methanol.
2
Yang, Haiyang, Huiyu Yang, and Xuemin Yan. "Low-Temperature Oxidation of Heavy Oil Asphaltene with and without Catalyst." Molecules 27, no. 20 (2022): 7075. http://dx.doi.org/10.3390/molecules27207075.
Full textAbstract:
In this study, the asphaltene extracted from Luntai heavy oil was oxidized by a mixture of propionic anhydride and hydrogen peroxide without and with a catalyst. Elemental analysis and infrared spectroscopy results indicated the occurrence of oxygen addition, condensation, and side chain cleavage reactions in the oxidation process. Oxidation products were divided into methanol solubles and methanol insolubles. The H/C and O/C atomic ratios of the MeOHS in the oxidation products without a catalyst were higher than those of the Luntai asphaltene. MeOHS had fewer aromatic rings than Luntai asphaltene. Compared with the oxidative reaction without a catalyst, the total mass of oxidation products and the proportion of MeOHS in oxidation products both increased after catalytic oxidation. This low-temperature oxidation technology can be used to upgrade asphaltenes, and thus can promote the exploitation and processing of heavy oil.
3
Maya-Cornejo, J., A. Ledesma-Durán, S. I. Hernández, and I. Santamaría-Holek. "Competitive Adsorption and Interplay between Methanol and Water During Electro-Oxidation on Pd-Based Electrocatalyst." Journal of The Electrochemical Society 169, no. 4 (2022): 046505. http://dx.doi.org/10.1149/1945-7111/ac6321.
Full textAbstract:
The methanol oxidation reaction on palladium-based materials at different concentrations is studied theoretically and experimentally through its electrochemical response. Using a well-established reaction mechanism for the methanol oxidation reaction under alkaline conditions, we analyze the role of methanol, water adsorption and oxidation steps on the total electrochemical current obtained from linear voltammetry experiments. Solving the kinetic equations numerically, we fit the data obtained from experiments performed with a commercial catalyst at different methanol concentrations. Comparison of the numerical calculations with analytical expressions deduced following Laviron’s theoretical approach leads to discerning the adsorption contributions from methanol and water to the overall shape of the oxidation current from the nonlinear contribution associated with carbon-dioxide production. This identification allows, in turn, to use the peak current of the adsorption-related processes as a tool to characterize the overall catalyst’s performance.
4
Miller, Aleksandr, Vasily Kaichev, Igor Prosvirin, and Valeriy Bukhtiyarov. "The Investigation of Catalytic Methanol Oxidation on Pt(111) and Pd(111) by X-Ray Photoelectron Spectroscopy and Mass-Spectrometry." Siberian Journal of Physics 4, no. 4 (2009): 31–41. http://dx.doi.org/10.54362/1818-7919-2009-4-4-31-41.
Full textAbstract:
Oxidation and dehydrogenation of methanol over Pt(111) and Pd(111) single-crystals were studied using in situ X-ray photoelectron spectroscopy (XPS) and mass-spectrometry. It was found that for both metals the methanol dehydrogenation proceeds via two routes: dehydrogenation to CO and hydrogen, and decomposition of methanol with C–O bond scission [1–3]. The rate of the second route is several times lower, however, carbon production in this case leads to formation of carbon deposits, which block the surface and hinder the catalytic reactions. Even in the presence of O2 in the gas phase, the main route of methanol conversion over Pd is dehydrogenation to CO and H2. Hydrogen is partially oxidized to water, and CO is oxidized to CO2. The reactions start at temperature above 450 K when surface carbon depositions are removed by oxygen. In contrast, over Pt in presence of O2, the main reaction products are CO2 and water. Reaction also starts above 450 K when the surface carbon deposits are removed. We suppose that the reaction comes via two stages: at first, methanol dehydrogenates to CO and H2, and then total oxidation of these intermediates occurs. At the same time we detected by in situ XPS the formation of formates on the Pt surface. It means that methanol over Pt partially oxidize via non-CO-involved route when the formation and following decomposition of surface formates lead to CO2 and H2 yield. The difference in product distribution over Pt and Pd in the methanol oxidation is in a good agreement with the fact that Pt is more active in the CO oxidation than Pd. In both cases, the active state in the methanol oxidation is Pt or Pd in the metallic state.
5
Jambula Dinesh Babu, Bhuvaneswari Santharam, and Kottai Muthu Arumugam. "Estimation of flavonoids and screening of in vitro antioxidant activity of various extracts of aerial parts of Blepharis maderaspatensis by hydroxyl radical and total antioxidant activity." International Journal of Research in Pharmaceutical Sciences 11, SPL4 (2020): 1204–9. http://dx.doi.org/10.26452/ijrps.v11ispl4.4266.
Full textAbstract:
Antioxidants are substances that hamper or inhibit the oxidation of oxidizable substrates in the cells. The aerial parts of Blepharis maderaspatensis dry powder was extracted with various solvents (PE, EA and methanol) through Soxhlet extractor. The aerial parts of different concentrates (Pet.ether, ethyl acetate and methanol) of Blepharis maderaspatensis was evaluated for its in-vitro antioxidant potential by hydroxyl radical, total antioxidant activity taking ascorbate used as standard for the both methods and total flavonoids content was estimated as equivalent to rutin. The methanolic concentrates of Blepharis maderaspatensis & standard exhibited antioxidant potential possessing IC50 210µg/ml & 62µg/ml (hydroxyl radical) 200µg/ml & 57µg/ml (Total antioxidant activity) respectively. An IC50 value was originate that methanolic concentrates of Blepharis maderaspatensis more efficient in hydroxyl radical, total antioxidant activity compared EA & PE concentrates. The methanolic and EA concentrates of Blepharis maderaspatensis showed the total flavonoids content (11.230±0.22 and 2.858±0.56 mg of rutin equivalent/g of powder) respectively. The difference in scavenging potential of the extracts can be due to variation in the percentage of bioactive compound flavonoids present in methanolic extracts. Invitro antioxidant studies obviously show methanolic concentrates of Blepharis maderaspatensis have better antioxidant activity due to the presence of total flavonoids content. The findings from the study reveal that the antioxidative potentials of methanolic concentrates Blepharis maderaspatensis could serve as free radical inhibitors, possibly acting as natural antioxidants.
6
Sakong, Sung, and Axel Gross. "Total Oxidation of Methanol on Cu(110): A Density Functional Theory Study." Journal of Physical Chemistry A 111, no. 36 (2007): 8814–22. http://dx.doi.org/10.1021/jp072773g.
Full text
7
Karapetsas, Athanasios, Georgia-Persephoni Voulgaridou, Manolis Konialis, et al. "Propolis Extracts Inhibit UV-Induced Photodamage in Human Experimental In Vitro Skin Models." Antioxidants 8, no. 5 (2019): 125. http://dx.doi.org/10.3390/antiox8050125.
Full textAbstract:
The aim of this study was to assess the antioxidant, photoprotective, and antiaging effects of Greek propolis. Propolis was subjected to n-heptane or methanol extraction. Total phenolic/flavonoid content and antioxidant potential were determined in the extracts. Promising extracts were evaluated for their cytoprotective properties using human immortalized keratinocyte (HaCaT) or reconstituted human skin tissue following exposure to UVB. Assessment of cytotoxicity, DNA damage, oxidative status, and gene/protein expression levels of various matrix metalloproteinases (MMPs) were performed. The propolis methanolic fractions exhibited higher total phenolic and flavonoid contents and significant in vitro antioxidant activity. Incubation of HaCaT cells with certain methanolic extracts significantly decreased the formation of DNA strand breaks following exposure to UVB and attenuated UVB-induced decrease in cell viability. The extracts had no remarkable effect on the total antioxidant status, but significantly lowered total protein carbonyl content used as a marker for protein oxidation in HaCaT cells. MMP-1, -3, -7, and -9, monitored as endpoints of antiaging efficacy, were significantly reduced by propolis following UVB exposure in a model of reconstituted skin tissue. In conclusion, propolis protects against the oxidative and photodamaging effects of UVB and could be further explored as a promising agent for developing natural antiaging strategies.
8
Limenew, Abate, Abebe Atakilt, and Mekonnen Alemayehu. "Studies on antioxidant and antibacterial activities of crude extracts of Plantago lanceolata leaves." Chemistry International 3, no. 3 (2017): 277–87. https://doi.org/10.5281/zenodo.1473326.
Full textAbstract:
In this study, three different antioxidant activity quantification methods: 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH), reducing power, FRAP and peroxide value determination including total phenolic, TP, total flavonoid, TF assays of crude leaf extracts of Plantago lanceolata were carried out. The extracts showed significant activities in all antioxidant assays in a concentration dependent manner. The crude extracts were found to possess higher ferric reducing activity ranging from 336.58±0.052 mgAAE/100g (90% methanol) to 172.94±0.032 mgAAE/100g (petroleum ether) and DPPH activity varied from 90.6% (90% methanol) to 36.04% (petroleum ether). Strong correlation of TPC with AEACDPPH and AEACFRAP (R2 = 0.9033 and R2 = 0.8538 respectively) implied that compounds in the extract were proficient to scavenge the DPPH free radical and reducing ferric ions into ferrous ions. Moreover, peroxide values of the extracts were obtained and varied from 19.8 meq/kg (90% methanol) to 379 meq/kg(petroleum ether) and 3.1meq/kg (90% methanol) to 119 meq/kg (petroleum ether) at 70 oC and room temperature respectively. Therefore, P. lanceolata leaf extracts as compared to the control showed effective activity in delaying oxidation of the oil. Antimicrobial capacity evaluation of crude extracts against different gram-positive and gram-negative organisms was also evaluated and a higher degree of antimicrobial activity was observed of crude extracts with MIC and MBC values in the range of 6.25 to 25% were also observed for the crude extracts.
9
Zhang, Feng Ming, and Chun Yuan Ma. "Supercritical Water Oxidation of Organics Wastewater a with a Novel Transpiring-Wall Reactor." Advanced Materials Research 531 (June 2012): 300–303. http://dx.doi.org/10.4028/www.scientific.net/amr.531.300.
Full textAbstract:
Supercritical water oxidation (SCWO) is a new technology for treating organic waste and recovering energy. This paper focuses on supercritical water oxidation of organics wastewater with a novel transpiring-wall reactor, and methanol solution was used as artificial wastewater. A coaxial burner allow the transition of the preheating of the feed from external to internal which prevent the plugging in the preheating section. The results show that methanol can be destructed completely with the outlet concentration of total organics carbon (TOC) was lower than 10 ppm. Higher temperatures are present inside the reactor at higher flux ratios of Ffeed/Fhot.
10
Khazzal Hummadi, Khalid, Karim H. Hassan, and Phillip C. H. Mitchell. "Selectivity and Activity of Iron Molybdate Catalysts in Oxidation of Methanol." Journal of Engineering Research [TJER] 6, no. 1 (2009): 1. http://dx.doi.org/10.24200/tjer.vol6iss1pp1-7.
Full textAbstract:
The selectivity and activity of iron molybdate catalysts prepared by different methods are compared with those of a commercial catalyst in the oxidation of methanol to formaldehyde in a continuous tubular bed reactor at 200-350 oC (473-623 oK), 10 atm (1013 kPa), with a methanol-oxygen mixture fixed at 5.5% by volume methanol: air ratio. The iron(III) molybdate catalyst prepared by co-precipitation and filtration had a selectivity towards formaldehyde in methanol oxidation comparable with a commercial catalyst; maximum selectivity (82.3%) was obtained at 573oK when the conversion was 59.7%. Catalysts prepared by reacting iron (III) and molybdate by kneading or precipitation followed by evaporation, omitting a filtration stage, were less active and less selective. The selectivity-activity relationships of these catalysts as a function of temperature were discussed in relation to the method of preparation, surface areas and composition. By combing this catalytic data with data from the patent literature we demonstrate a synergy between iron and molybdenum in regard to methanol oxidation to formaldehyde; the optimum composition corresponded to an iron mole fraction 0.2-0.3. The selectivity to formaldehyde was practically constant up to an iron mole fraction 0.3 and then decreased at higher iron concentrations. The iron component can be regarded as the activity promoter. The iron molybdate catalysts can thus be related to other two-component MoO3-based selective oxidation catalysts, e.g. bismuth and cobalt molybdates. The iron oxide functions as a relatively basic oxide abstracting, in the rate-controlling step, a proton from the methyl of a bound methoxy group of chemisorbed methanol. It was proposed that a crucial feature of the sought after iron(III) molybdate catalyst is the presence of -O-Mo-O-Fe-O-Mo-O- groups as found in the compound Fe2(MoO4)3 and for Fe3+ well dispersed in MoO3 generally. At the higher iron(III) concentrations the loss of selectivity is due to the presence of iron oxide patches or particles which catalyze the total oxidation of methanol, and the loss of activity to blocking of molybdenum sites.
11
Gong, Gui Zhen, Ji Ming Chu, Xian Yong Wei, and Zhi Min Zong. "Analysis of Extraction of Coal Oxidation Residue in NaOCl." Advanced Materials Research 724-725 (August 2013): 1103–6. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.1103.
Full textAbstract:
Sequential extraction of four coal oxidation residues (COR) from aqueous NaOCl solution with petroleum ether (PE), carbon disulfide (CS2), acetone and methanol were investigated. The results suggest that methanol is an effective extraction solvent, giving the highest extraction yields for four COR. The extraction fractions were analyzed by GC/MS. It is found that no compounds, except for F1 of HL and XL , F2 of four COR, were detected. In total, 89 organic compounds were detected in F1 of HL and XL, 23 organic compounds in F2 from four COR. Most of which were arenes (As), normal alkanes (NAs) and oxygen-containing compounds (OCCs).
12
Setiawati, Ajeng Retno, and Shirly Gunawan. "Uji Fitokimia, Kapasitas Total Antioksidan, Bslt Serta Kadar Total Fenolik pada Ekstrak Daun Meniran (Phyllanthus Niruri L.)." Syntax Literate ; Jurnal Ilmiah Indonesia 8, no. 6 (2023): 4521–28. http://dx.doi.org/10.36418/syntax-literate.v8i6.12742.
Full textAbstract:
Indonesians believe in a tradition passed from generation to generation about the properties of herbal medicine. Meniran leaf is one of the ber grown in Asia and found in many parts of Indonesia. It contains flavonoids and alkaloid able to stimulate the immune system and antioxidants to combat ROS. Antioxidant can neutralize the effects caused by oxidative stress (a conndition where the is an imbbalance between oxidants and antioxidants in the body). Antioxidants can prevent degenerative diseases and malignancies caused by prolonged oxidative stress. Because of its ability to prevent oxidation, this study uses meniran leaves to further investigate its uses. This study aims to look into meniran leaves’ phytochemical constituents, antioxidant capacity, and toxicity. Meniran leaves extract was made by maseration using methanol, phytochemical screening used Harborne’s method, antioxidant capacity used Blois’ DPPH (1,1-diphenyl-2-picrylhydrazil) method, total phenolic content used Singleton’s method, and toxicity with BSLT. Phytochemical screening of meniran leaf extract determined that it contains alkaloids, flavonoids, cardioglycosides, glycosides, saponins, coumarins, phenolics, quinones, betacyanins, steroids, terpenoids, and tannins. Its antoxidant capacity ((IC50 =81.585µg/mL), total phenolic content (10,295µg/mL), total alkaloid content (13.788 µg/mL), and toxicity (LC50 =170.308 μg/mL) which can be considered to have a cytotoxic effect and categorized as moderate (100 ppm ≤ LC50 ≤ 1000 ppm). In summary, meniran leaf extract has the potential to be an antioxidant with an antimitotic effect
13
Tsoncheva, Tanya, Krasimir Ivanov, and Dimitar Dimitrov. "Copper and chromium oxide nanocomposite catalysts for simultaneous elimination of CO and oxygenate VOCs in toxic gas emissions." Canadian Journal of Chemistry 89, no. 5 (2011): 583–89. http://dx.doi.org/10.1139/v11-037.
Full textAbstract:
Copper and chromium oxide nanocomposite materials with different Cu/Cr ratios were prepared by impregnation of a conventional silica support with toluene solutions of the corresponding acetylacetonate precursors and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–vis spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction–thermogravimetric methods. Their catalytic behaviour in the total oxidation of CO and different oxygenate VOCs (methanol, dimethyl ether, and ethyl acetate) was tested. The relation between the phase composition and catalytic properties of the materials was also analyzed. It was established that materials with a 1:2 CuO/Cr2O3 molar ratio exhibit high catalytic activity for dimethyl ether oxidation, those with 2:1 and 1:1 ratios are suitable for CO and methanol oxidation, respectively, and both of the latter, but at much higher temperatures, are good for ethyl acetate elimination. A catalyst with an optimal composition of 1:1 (mol/mol) CuO/Cr2O3, working in a reactor with three temperature zones of 490–500 K, 570–580 K, and 620–630 K, is proposed for the effective simultaneous elimination of CO, methanol, ethyl acetate, and dimethyl ether in toxic emissions.
14
Pham, Tung Ngoc, Ajaikumar Samikannu, Solomon Tesfalidet, Thomas Wågberg, and Jyri-Pekka Mikkola. "NiCo Nanoneedles on 3D Carbon Nanotubes/Carbon Foam Electrode as an Efficient Bi-Functional Catalyst for Electro-Oxidation of Water and Methanol." Catalysts 11, no. 4 (2021): 500. http://dx.doi.org/10.3390/catal11040500.
Full textAbstract:
In this study, we report a 3D structured carbon foam electrode assembled from a bi-functional NiCo catalyst, carbon nanotubes (CNT), and a monolith 3D structured carbon foam (CF) as a highly active and stable electrode for oxygen evolution reaction (OER) and methanol oxidation reaction (MOR). When the NiCo@CNTs/CF electrode was used as an anode in OER, after the anodization step, the electrode required a small overpotential of 320 mV to reach the current density of 10 mA cm−2 and demonstrated excellent stability over a long testing time (total 30 h) in 1 M KOH. The as-prepared NiCo@CNTs/CF electrode also exhibited a good performance towards methanol oxidation reaction (MOR) with high current density, 100 mA cm−2 at 0.6 V vs. Ag/AgCl, and good stability in 1 M KOH plus 0.5 M CH3OH electrolyte. The NiCo@CNTs/CF catalyst/electrode provides a potential for application as an anode in water electrolysis and direct methanol fuel cells.
15
Stoiljkovic, Zora, Milka Jadranin, Svetlana Djuric, Slobodan Petrovic, Avramov Ivic, and Dusan Mijin. "Investigation of forced and total degradation products of amlodipine besylate by liquid chromatography and liquid chromatography-mass spectrometry." Chemical Industry and Chemical Engineering Quarterly 20, no. 2 (2014): 295–304. http://dx.doi.org/10.2298/ciceq121226011s.
Full textAbstract:
An isocratic, reversed-phase liquid chromatographic method was applied for the investigation of the degradation products of amlodipine besylate under the stressed conditions in solution. Amlodipine besylate stock solutions were subjected to acid and alkali hydrolysis, chemical oxidation and photodegradation as well as to the electrochemical degradation by cyclic voltammetry in 0.05 mol/L NaHCO3 on gold electrode. The total degradation of amlodipine besylate was achieved in 5 mol/L NaOH at 80?C for 6 h and the compound with molecular formula C15H16NOCl was identified as a main degradation product. Under acidic (5 mol/L HCl at 80?C for 6 h) stress conditions 75.2% of amlodipine besylate degradation was recorded. Oxidative degradation in the solution of 3% H2O2-methanol 80:20 at 80?C for 6 h showed that amlodipine besylate degraded to 80.1%. After 14 days of expose in photostability chamber amlodipine besylate solution showed degradation of 32.2%. In electrochemical degradation after 9 hours of cyclization the beginning of amlodipine oxidation was shifted for 200 mV to more negative potentials, with the degradation of 66.5%. Mass spectrometry analysis confirmed the presence of dehydro amlodipine derivate with molecular formula C20H23N2O5Cl in oxidative and acidic conditions while in electrochemical degradation was detected in traces.
16
Guo, Yuyu, Shen Zhang, Jing Zhu, Liqing Su, Xianmei Xie, and Zhe Li. "Effects of Pt on physicochemical properties over Pd based catalysts for methanol total oxidation." Applied Surface Science 416 (September 2017): 358–64. http://dx.doi.org/10.1016/j.apsusc.2017.04.205.
Full text
17
Wang, Dongliang, Jingwei Li, Wenliang Meng, et al. "Integrated Process for Producing Glycolic Acid from Carbon Dioxide Capture Coupling Green Hydrogen." Processes 10, no. 8 (2022): 1610. http://dx.doi.org/10.3390/pr10081610.
Full textAbstract:
A novel process path is proposed to produce glycolic acid (GA) from CO2 as the feedstock, including CO2 capture, power-to-hydrogen, CO2 hydrogenation to methanol, methanol oxidation to formaldehyde, and formaldehyde carbonylation units. The bottlenecks are discussed from the perspectives of carbon utilization, CO2 emissions, total site energy integration, and techno-economic analysis. The carbon utilization ratio of the process is 82.5%, and the CO2 capture unit has the largest percentage of discharge in carbon utilization. Among the indirect emissions of each unit, the CO2 hydrogenation to methanol has the largest proportion of indirect carbon emissions, followed by the formaldehyde carbonylation to glycolic acid and the CO2 capture. After total site energy integration, the utility consumption is 1102.89 MW for cold utility, 409.67 MW for heat utility, and 45.98 MW for power. The CO2 hydrogenation to methanol makes the largest contribution to utility consumption due to the multi-stage compression of raw hydrogen and the distillation of crude methanol. The unit production cost is 834.75 $/t-GA; CO2 hydrogenation to methanol accounts for the largest proportion, at 70.8% of the total production cost. The total production cost of the unit depends on the price of hydrogen due to the currently high renewable energy cost. This study focuses on the capture and conversion of CO2 emitted from coal-fired power plants, which provides a path to a feasible low-carbon and clean use of CO2 resources.
18
Pashazadeh, Sara, Biuck Habibi, Ali Pashazadeh, Ali Fatemi, and Milad Rasouli. "(Digital Presentation) Facile Fabrication of Graphene Quantum Dot- Doped Polyaniline Embedded Cu Metal-Organic Frameworks Composite Electrode As Improved Anode Electrocatalyst for Methanol Oxidation." ECS Meeting Abstracts MA2022-01, no. 41 (2022): 2491. http://dx.doi.org/10.1149/ma2022-01412491mtgabs.
Full textAbstract:
Nonrenewable energy sources accounted for roughly 80% of total energy consumption [1]. Solar energy, wind energy, geothermal energy, hydropower, and fuel cells (FCs) have all recently been described as renewable energy sources. In commercial uses, renewable energy has experienced meteorological and logistical obstacles. Because of advantages such as simple fabrication/operation conditions, eco-friendly, high energy conversion efficiency, and long-term durability, FCs technologies are considered one of the most important renewable energy sources for many applications such as portable devices, cars, and electricity plants [2–5]. Methanol can be utilized in direct methanol fuel cells (DMFC) to produce clean energy that can be used in smart electronic gadgets or small automobiles in this regard [6]. However, before DMFC can be used commercially, the slow oxidation kinetics and catalyst toxicity [7] must be resolved. Therefore, the development of direct methanol fuel cells (DMFCs) is one of the most promising technologies for the applications of these devices in stationary power supplies and electric vehicles [8]. Apart from the future of mobile devices such as mobile chargers, phones, computers, and many other applications, this energy is environmentally benign because no gases are emitted and the waste is simply clean water. The biggest issue that this technique may encounter is its high cost due to the usage of noble metal catalysts (platinum (Pt) and ruthenium (Ru)) [9]. Methanol is oxidized via a multi-electron process and several products and/or intermediates can be formed, depending on the electrolyte and the nature of the electrode. Electrode materials are important parameters in the electrochemical oxidation of methanol, where high efficient electrocatalysts are needed. Several metal oxides such as Fe2O3, CeO2, MoOx, Co3O4, NiO, and CuO has been used in various applications, such as catalysis, water splitting photocatalysis, solar cells and gas sensing, besides their uses to enhance the electrocatalytic activity for methanol oxidation [10-11]. This paper describes the preparation of graphene quantum dot-doped polyaniline embedded copper metal-organic frameworks composite catalysts for investigating methanol oxidation in alkaline solutions. The electrode surface was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). After physicochemical characterizations of graphene quantum dot-doped polyaniline embedded copper metal-organic frameworks composite modified carbon ceramic electrode (Cu- MOF/GQDs-PAN/CCE), its electrocatalytic and stability characterizations toward methanol oxidation in alkaline media were investigated in detail by cyclic voltammetry and chronoamperometry. Results showed that, the electrocatalytic activity of the Cu- MOF/GQDs-PAN/CCE electrode is much higher than those of unmodified electrode under similar experimental conditions, showing the possibility of attaining good electrocatalytic anodes for fuel cells. Kinetic parameters such as the electron transfer coefficient (α) and the number of electrons involved in the rate determining step (nα) for the oxidation of methanol were determined utilizing cyclic voltammetry (CV). Keywords: Graphene quantum dot, Polyaniline, Metal-organic frameworks, electrocatalyst, Methanol References [1] S.K. Kamarudin, F. Ahmad, W.R.W. Daud, Overview on application of direct methanol fuel cell (DMFC) for portable electronic devices, Int. J. Hydrog. Energy 34 (2009) 6902–6916. [2] L. Carrette, K.A. Friedrich, U. Stimming, Fuel cells: principles, types, fuels and applications, ChemPhysChem 1 (2000) 162–193. [3] A.B. Stambouli, Fuel cells: The expectations for an environmental-friendly and sustainable source of energy, Renew. Sustain. Energy Rev. 15 (9) (2011) 4507– 4520. [4] P. Joghee, J.N. Malik, S. Pylypenko, R. O’Hayre, A review on direct methanol fuel cells – In the perspective of energy and sustainability, MRS Energy Sustain. 2 (2015), https://doi.org/10.1557/mre.2015.4. [5] D. Hassen, M.A. Shenashen, S.A. El-Safty, M.M. Selim, H. Isago, A. Elmarakbi, H. Yamaguchi, Nitrogen-doped carbon-embedded TiO2 nanofibers as promising oxygen reduction reaction electrocatalysts, J. Power Sources 330 (2016) 292– 303. [6] M. Mansor, S.N. Timmiati, K.L. Lim, W.Y. Wong, S.K. Kamarudin, N.H. Nazirah Kamarudin, Recent progress of anode catalysts and their support materials for methanol electrooxidation reaction, Int. J. Hydrogen Energy 44 (29) (2019) 14744–14769, https://doi.org/10.1016/j.ijhydene.2019.04.100. [7] Z. Mousavi, A. Benvidi, S. Jahanbani, M. Mazloum-Ardakani, R. Vafazadeh, H. R. Zare, Investigation of electrochemical oxidation of methanol at a carbon paste electrode modified with Ni(II)-BS complex and reduced graphene oxide nano sheets, Electroanalysis 28 (12) (2016) 2985–2992, https://doi.org/10.1002/ elan.201501183. [8] S. Wasmus, A. Küver, Methanol oxidation and direct methanol fuel cells: a selective review, J. Electroanal. Chem. 461 (1-2) (1999) 14–31. [9] M. Liu, R. Zhang, W. Chen, Graphene-Supported Nanoelectrocatalysts for Fuel Cells: Synthesis, Properties, and Applications, Chem. Rev. 114 (2014) 5117– 5160. [10] N. Spinner, W.E. Mustain, Electrochim. Acta 56 (2011) 5656. [11] M.S. Risbud, S. Baxter, M. Skyllas-Kazacos, Open Fuels Energy Sci. J. 5 (2012) 9.
19
Tsoncheva, Tanya, Gloria Issa, Radostina Ivanova, et al. "Design Control of Copper-Doped Titania–Zirconia Catalysts for Methanol Decomposition and Total Oxidation of Ethyl Acetate." Symmetry 14, no. 4 (2022): 751. http://dx.doi.org/10.3390/sym14040751.
Full textAbstract:
This study is focused on the design control of Cu–Zr–Ti oxide composites by the variation of the Zr/Ti ratio and the copper deposition procedure used. For the first time, these ternary composites were obtained by a combination of template-assisted hydrothermal techniques for the preparation of mesoporous ZrO2–TiO2 mixed oxides with diverse compositions, followed by the consecutive chemisorption and hydrolysis of copper ammonia complexes on them. The nitrogen physisorption, XRD, SEM, HRTEM, TPR, XPS, UV-Vis, and Raman spectroscopies were applied for the catalysts’ characterization. Methanol decomposition and the total oxidation of ethyl acetate, both of which with potential for sustainable environmental protection, were used as catalytic tests. The complex relationship between the phase composition, structure, and morphology of titania–zirconia mixed oxides and the state and catalytic behavior of the copper oxide species supported on them was investigated. In comparison with the conventional impregnation technique, the novel preparation procedure revealed the generation of more uniform and homogeneously dispersed needle-like copper oxide crystallites in the mesoporous TiO2–ZrO2 host matrix, which typically ensure improved catalytic performance. The synergistic activity between the loaded copper species and TiO2–ZrO2 support was discussed. All ternary composites exhibited superior catalytic activity in total oxidation of ethyl acetate. The specific behavior of the catalysts in methanol decomposition was related to the irreversible phase transformations by the influence of the reaction medium.
20
Kim, I.-Tae, Ye-Eun Lee, Yeong-Seok Yoo, et al. "Development of a Combined Aerobic–Anoxic and Methane Oxidation Bioreactor System Using Mixed Methanotrophs and Biogas for Wastewater Denitrification." Water 11, no. 7 (2019): 1377. http://dx.doi.org/10.3390/w11071377.
Full textAbstract:
We developed a lab-scale aerobic–methane oxidation bioreactor (MOB)–anoxic system, combining a MOB and the aerobic–anoxic denitrification process, and evaluated its potential for advanced nitrogen treatment in wastewater treatment plants (WWTPs). The MOB used biogas generated from a WWTP and secondary-treated wastewater to support mixed methanotroph cultures, which mediated the simultaneous direct denitrification by methanotrophs and methanol production necessary for denitrifying bacteria in the anoxic chamber for denitrification. Compared to the aerobic–anoxic process, the aerobic–MOB–anoxic system with an influent concentration of 4.8 L·day−1 showed a marked increase in the reduction efficiency for total nitrogen (41.9% vs. 85.9%) and PO4−3-P (41.1% vs. 69.5%). However, the integrated actions of high nitrogen and phosphorus consumption are required for methanotroph growth, as well as the production and supply of methanol as a carbon source for denitrification and methane monooxygenase-mediated oxidation of NH3 into N2O by methanotrophs. After three months of continuous operation using actual wastewater, the total nitrogen removal rate was 76.3%, equivalent to the rate observed in a tertiary-advanced WWTP, while the total phosphorus removal rate reached 83.7%.
21
Elwan, Hamada, Abdelhameed S. A. Mohamed, Dawood Hosni Dawood, and Shaaban S. Elnesr. "Modulatory Effects of Arctostaphylos uva-urs Extract In Ovo Injected into Broiler Embryos Contaminated by Aflatoxin B1." Animals 12, no. 16 (2022): 2042. http://dx.doi.org/10.3390/ani12162042.
Full textAbstract:
In ovo injection of nutrients can modulate the embryo’s physiological responses against aflatoxin B1 (AFB1) embryotoxicity. This hypothesis was tested using in ovo injection of Arctostaphylos uva-ursi (Ar. uu.) methanolic extract. The total polyphenols, total flavonoids, total antioxidant capacity, and GC-MS analysis were all assessed in the Ar. uu. methanolic extract. A total of 180 ten-day-old embryonated eggs were distributed into six groups of 30 replicates each. The first group was used as a control (non-injected), and the second, third, fourth, fifth, and sixth groups were injected with 10 µ double-distilled water (DDW), 500 µL methanol, 0.01 g Ar. uu./500 µL methanol, 50 ng AFB1/10 µL DDW, and 50 ng AFB1 in 10 µ DDW + 0.01 g Ar. uu./500 µL methanol, respectively. The relative embryo weight, residual yolk sac weight, tibia length and weight, and survival were recorded. Total and differential leukocytes, oxidative stress, and humoral immune responses were observed. The residual yolk sac was lower (p < 0.05) in the Ar. uu. group than other groups. The embryonic growth (tibia weight and length) was enhanced in AFB1 + Ar. uu.-injected embryos compared with those injected with AFB1 alone. In conclusion, in ovo injection of Arctostaphylos uva-ursi could modulate AFB1-induced toxicity in chicken embryos.
22
Zhu, Yimin, Hiroyuki Uchida, Takahiro Yajima, and Masahiro Watanabe. "Attenuated Total Reflection−Fourier Transform Infrared Study of Methanol Oxidation on Sputtered Pt Film Electrode." Langmuir 17, no. 1 (2001): 146–54. http://dx.doi.org/10.1021/la000457m.
Full text
23
Zhang, Shen, Yuyu Guo, Xingying Li, and Zhe Li. "Effects of cerium doping position on physicochemical properties and catalytic performance in methanol total oxidation." Journal of Rare Earths 36, no. 8 (2018): 811–18. http://dx.doi.org/10.1016/j.jre.2018.01.012.
Full text
24
Genoni, Fausto, Gian Piero Casati, Roberto Buzzoni, et al. "FTIR and Thermogravimetric Study of Silicalite Treated with Methanol." Collection of Czechoslovak Chemical Communications 62, no. 10 (1997): 1544–50. http://dx.doi.org/10.1135/cccc19971544.
Full textAbstract:
FTIR and TGA-DTA techniques were used for the high-defective Al-Na free silicalite characterization. Methanol reacting with external and internal silanols provides a sample modification evidenced by the combined use of these two techniques. A quantitative correlation between the FTIR and TGA data was drawn out although the incomplete methoxylation did not allow to quantify the total number of silanols. At least two distinct types of methoxylated sites were found according to their oxidation temperature which is unexpectedly high for one of them.
25
Roman, Nebesnyi, Pikh Zorian, Kubitska Iryna, Orobchuk Oksana, and Lukyanchuk Andrii. "ACRYLIC ACID SYNTHESIS BY OXIDATIVE CONDENSATION OF METHANOL AND ACETIC ACID ON B–P–V–W–OX/SIO2 CATALYST." Eastern-European Journal of Enterprise Technologies 1, no. 6 (97) (2019): 21–27. https://doi.org/10.15587/1729-4061.2019.156764.
Full textAbstract:
The process of oxidative condensation of methanol with acetic acid to acrylic acid on B–P–V–W–Ox/SiO<sub>2</sub> catalyst modified by hydrothermal method has been studied. Modification of the catalyst by hydrothermal treatment of the carrier changes its physical and chemical properties, and therefore its catalytic properties. The influence of the main technological parameters – temperature, contact time and ratio of reagents on the selectivity and yield of the reaction products and on the conversion of acetic acid has been studied when hydrothermally treated catalyst was used. The best time of contact was 8 sec. which allows to reach the highest selectivity and yield of acrylic acid and methyl acrylate. The highest catalytic activity of the designed catalyst is observed at the reaction temperature of 673 K, however, it is impossible to increase temperature over this value due to the limited thermal stability of the catalyst and the sharp increase in the formation of complete oxidation products. With an increase of methanol part in the ratio of reagents (methanol: acetic acid) to 1,2:1, the selectivity of acrylic acid and methyl acrylate increases, and the selectivity of by-products is significantly reduced. The highest yield of the target products in the reaction of oxidative condensation of methanol with acetic acid is observed at a ratio of oxygen: acetic acid 1,5:1. The growth of the oxygen: acetic acid ratio promotes reduce of acetone and methyl acetate selectivity but does not change the selectivity of methyl acrylate and significantly increases the selectivity and yield of acrylic acid. At the best conditions of the reaction it was possible to achieve 54.7 % total yield of acrylic acid and methyl acrylate. Due to the wide availability and relatively low cost of the initial reagents (methanol and acetic acid), the synthesis of acrylic acid by the oxidative condensation of methanol with acetic acid in the presence of the developed catalyst is very
26
Balzarotti, Riccardo, Andrea Basso Peressut, Gabriella Garbarino, et al. "A Study of Redox Properties of Ceria and Fe-Ceria Solid Materials Through Small Molecules Catalytic Oxidation." Materials 18, no. 4 (2025): 806. https://doi.org/10.3390/ma18040806.
Full textAbstract:
This work presents a study of the redox properties of CeO2 particles with (FeCeHS) and without (CeHS) Fe2O3 impregnation, as possible innovative catalysts for oxidation and combustion reactions as well as CO2 activation. The topic, therefore, is part of a broader analysis of environmental catalysis, which aims to reduce the emissions of polluting substances and improve the exploitation of energy resources, with consequent progress in the eco-friendly field. Different laboratory techniques (Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Ultraviolet–Visible (UV-Vis), and Fourier Transform–Infrared (FT-IR) spectroscopies) point out that iron oxide is deposited on the surface of ceria, which maintains its lattice structure, although the particle morphology is slightly changed. Methanol and ethanol adsorption and conversion were evaluated on these catalysts by Temperature Programmed Surface Reaction (TPSR) and by in situ FT-IR spectroscopy of the probe redox properties, evidencing the formation of surface oxidized intermediates and combustion products. The FeCeHS catalyst demonstrates, in our reaction conditions, a good combustion activity in total oxidation of oxygenated molecules, hindering the formation of formaldehyde from methanol and reducing the quantity of CO produced by the partial oxidation reaction. A cooperative effect is suggested by the mixture of these two metals in the oxidation process.
27
Danet, Andrei E., Mihaela Oancea, Silviu Jipa, and Tanta Setnescu. "FLOW INJECTION ANALYSIS FOR METHANOL WITH ALCOHOL OXIDASE AND CHEMILUMINESCENT DETECTION." SOUTHERN BRAZILIAN JOURNAL OF CHEMISTRY 2, no. 2 (1994): 105–20. http://dx.doi.org/10.48141/sbjchem.v2.n2.1994.106_1994.pdf.
Full textAbstract:
A highly sensitive flow injection system was developed for the methanol determination. The system is based on the oxidation of methanol in the presence of alcohol oxidase to yield formaldehyde and hydrogen peroxide. The concentration of the hydrogen peroxide produced was determined by luminol chemiluminescence. A four-line flow injection assembly was used. The sample was injected into a flow of phosphate buffer at pH 9 that merged with a flow containing alcohol oxidase. The enzymatic reaction takes place in a coiled tube, 2 meters · long and 0.8 mm i.d. Just in front of the chemiluminescence cell, the flow containing the sample merged with a flow of luminol (1.5 mM) and potassium ferricyanide (20 mM). The injected volume was 50 pL and the total flow rate 1.6 mL min·1 The determination range was 5x10"4 -1x10'2 %(v/v) methanol. The throughput was 40 samples per hour. From 20 tested substances, only L-cysteine generated a signal comparable with that of methanol. The others, at concentrations equal to those of methanol, either gave no signal at all (n-butanol, cyclo-hexanol, glycine, L-threonine, L-proline, copper sulphate) or gave signals much smaller than that of methanol.
28
de Oliveira Polanco, Nataly Soares, Juan Carlo Villalba, Fauze Jacó Anaissi, Almir Oliveira Neto, and Estevam Vitório Spinacé. "INFLUENCE OF SYNTHESIS TIME IN THE PROPERTIES OF PtRu/CARBON HYBRIDS PREPARED BY HYDROTHERMAL CARBONIZATION METHOD." PERIÓDICO TCHÊ QUÍMICA 20, no. 44 (2023): 01–14. http://dx.doi.org/10.52571/ptq.v20.n44.2023_01_tusi_pgs_01_14.pdf.
Full textAbstract:
Background: PtRu/C electrocatalysts present good results in methanol electo-oxidation. The activity of these electrocatalysts is strongly dependent on the synthesis method. Additionally, the use of mesoporous carbons or nanostructured carbons increases the performance of electrocatalysts applied in alcohol electro-oxidation. The hydrothermal carbonization method is an alternative to obtain different nanoarchitectures without involving harsh conditions. Aims: Thus, this work aimed to evaluate the influence of synthesis time on the properties of PtRu/Carbon hybrids prepared by the hydrothermal carbonization method. Methods: PtRu/Carbon hybrids were prepared by hydrothermal carbonization at different times of synthesis (6 h and 12 h). It used cellulose as a carbon source and reducing agent and H2PtCl6.6H2O and RuCl3.xH2O as metal sources and catalysts of the carbonization process. The materials were treated at 900 °C and characterized by energy-dispersive X-ray spectroscopy, thermogravimetric analysis, B.E.T isotherms, X-ray diffraction, transmission electron microscope and cyclic voltammetry. The electro-oxidation of methanol was studied by chronoamperometry. Results: The increase in synthesis time from 6 to 12 hours, apparently, resulted in an increase in mean particle size, reduction of mesoporous volume and increase in superficial area and total pore volume. The chronoamperometry of methanol electro-oxidation on these PtRu/Carbon hybrids indicated a higher electroactivity to the material prepared in 6 hours. Discussion: Probably, the higher electroactivity of material prepared in 6 h is associated with smaller particle size, mesoporous structure and surface oxides content. Conclusions: Therefore, it is possible to affirm that the synthesis time is an important parameter that affects the physical-chemical properties of metal/carbon hybrids obtained by the hydrothermal carbonization method.
29
OJ, Enema UF Umoh PS Thomas SK Adesina and OA Eseyin. "Phytochemical And Antioxidant Studies Of Leaf Of Tetrapleura Tetraptera (Schum and Thon) Taubert (Mimosaceae)." British Journal of Pharmaceutical and Medical Research 04, no. 03 (2019): 1865–75. https://doi.org/10.24942/bjpmr.2019.0490.
Full textAbstract:
Tetrapleura tetraptera (Schum and Thon) Taubert (Mimosaceae) has numerous ethnopharmacological relevance, the plant has played significant roles in the management of numerous health conditions including ulcer, inflammations, arthritis, malaria and even as molluscicidal agent. This research was aimed at evaluating the phytochemical and antioxidant properties of both fractions and volatile oil of leaf of T. tetraptera. Soxhlet apparatus was used in extraction of the leaves into fractions of n-hexane, dichloromethane, ethyl acetate, and methanol, respectively. Determination of total phenolic content, ferric reducing powers (FRAP) assay, and 2,2- diphenyl-1- picrylhydrazyl (DPPH) radical scavenging assay, were used to determine the antioxidant power. Isolation and purification of volatile oils of n-hexane fraction involved chromatographic techniques. Results of total phenolic content showed that methanol fraction had highest phenolic content of 16.66±0.0012 mg, and 4.165 mg GAE/g, and this is statistically significance at p<0.001. DPPH radical scavenging activity assay also showed an increase in percentage inhibition with a corresponding increase in concentration, sample NH1 (volatile oil) showed greater percentage inhibition of 80 %, and was statistically significant at p<0.001. The FRAP assay also showed an increase in percentage inhibition with a corresponding increase in concentration, this is also significant at p<0.001. The GC-MS of the volatile oil showed the presence of 25 compounds which are basically esters, terpenoids, alkenes, alkanes and fatty acids. From the results of this study, it can be inferred that various fractions and volatile oil of leaf of T. tetraptera may be used as antioxidant agents.
30
Abbas, Ali, Bushra Sultana, Anwaar Hussain, Farooq Anwar, and Naveed Ahmad. "Antioxidant Potential, Phenolics Content and Antimicrobial Attributes of Selected Medicinal Plant." Pakistan Journal of Analytical & Environmental Chemistry 22, no. 2 (2021): 307–19. http://dx.doi.org/10.21743/pjaec/2021.12.10.
Full textAbstract:
The bioactive extracts recovered from Curcuma longa (stem), Mentha aquatica (stem and leaves), Emblica officinalis (fruits), Nigella sativa (seeds), and Glycyrrhiza glabra (stem) using methanol and ethanol, were appraised for antioxidant (total flavonoid contents, total phenolic contents, DPPH free radical scavenging ability, inhibition of linoleic acid peroxidation and reducing power) and antimicrobial attributes. Total phenolics (16.89 ± 0.18 - 25.06 ± 0.31g GAE/100g) and total flavonoids (1.96 ± 0.07 - 13.54 ± 0.18 CE g/100g) contents of aqueous methanol extracts of tested plant materials were significantly (p < 0.05) lower than that of aqueous ethanol extracts (13.87 ± 0.12 - 28.63 ± 0.34 g GAE/100g) and (2.20 ± 0.10 - 8.71 ± 0.24 CE /100g), respectively. The percent inhibition of linoleic acid per oxidation by crude ethanol extracts of plants was in the range of 48.72 ± 1.24 - 70.79 ± 1.57 and crude methanol extract 35.90 ± 1.28 - 61.54 ± 2.14, while the range of DPPH free radical scavenging activity of ethanol extracts was (58.36 ± 1.98 - 80.55 ± 3.07) and methanol extracts (39.55 ± 1.52 - 79.64± 2.33). The reducing power of the tested extracts obtained by ethanol (at the concentration of 10 mg/mL) ranged 1.11 ± 0.12 – 1.53 ± 0.18 while for methanol extracts 0.98 ± 0.11 – 1.39 ± 0.12. Among the attributes analyzed, total phenolics, total flavonoids, and DPPH free scavenging activity were found to be varied significantly in all the tested medicinal plants. The extracts from all plants showed good antimicrobial potential against a penal of bacteria, including E. coli, P. multocida and S. aureus, and fungi including A. niger, A. flavus, A. alternate, and G. lucidium. Overall, the tested samples were found to be a good source of natural antioxidant and antimicrobial agents and thus can be explored for potential functional food and nutra-pharmaceutical applications.
31
Phan, Duy The, Triet Duy Anh Ngo, and Quoc Kien Giang. "EFFECT OF EXTRACTION CONDITIONS ON TOTAL POLYPHENOL CONTENTS AND ANTIOXIDANT ACTIVITY OF PASSION FRUIT (Passiflora edulis) PEELS." TRA VINH UNIVERSITY JOURNAL OF SCIENCE; ISSN: 2815-6072; E-ISSN: 2815-6099 12, no. 49 (2022): 82–88. http://dx.doi.org/10.35382/tvujs.12.49.2022.1403.
Full textAbstract:
Passion fruit peel has been extracted by two methods, traditional extraction, and ultrasonic-assisted extraction to obtain the highest polyphenol content and to assess their antioxidant activity. For the traditional extractionmethod, the highest polyphenol content obtained under conditions of using methanol solvent with the ratio of material/solvent was 1/20 (g/mL) for 60 minutes at a temperature of 60oC. Under these conditions, the polyphenol content was 6.19 mg GAE/g DM (dry matter), the ability to resist oxidation by DPPH (IC50), FRAP,ABTS+ methods were 446 mg/ml, 3.32 mg Fe2+/g DM, 12.93 mg TE/g DM, respectively. With the ultrasound-assisted extraction method, the highest polyphenol content was obtained under the use of methanol for solvent, with a power capacity of 45%, a run time of 12 minutes, and a material/solvent ratio of 1/40 (g/mL). Under these conditions, the polyphenol content was 7.35 mg GAE/g DM, the ability to antioxidant determinedby DPPH (IC50), FRAP, and ABTS+ methods was 344 mg/mL, 3.89 mg Fe2+/g DM, 14.67 mg TE/g DM, respectively.
32
Phan, Vi T. T., Quy Phu Nguyen, Bin Wang, and Ian Burgess. "Elucidating Pathways of Methanol Oxidation on Oxygen-Vacant NiOOH Sites Using a Synergistic in Situ Attenuated Total Reflectance Surface-Enhanced Infrared Absorption Spectroscopy and DFT Study." ECS Meeting Abstracts MA2024-01, no. 44 (2024): 2406. http://dx.doi.org/10.1149/ma2024-01442406mtgabs.
Full textAbstract:
A thorough comprehension of the mechanism underlying the methanol oxidation reaction (MOR) on Ni-based catalysts is critical for electrocatalysis design and development of Ni-based alloys. However, the mechanism of MOR on these materials remains a matter of controversy. There have been few publications on employing surface enhanced spectroscopy to adequately capture the surface chemistry of MOR on NiOOH while the existing theoretical chemistry studies on the reaction mechanism presents a multitude of inconsistent and incomplete results. Here, we combine in situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) to determine the mechanism and product distribution of MOR on monometallic Ni-based catalysts in alkaline media. Critically, the DFT calculations include the role of O-vacancy of NiOOH, which is argued to be the active site for methanol oxidation. The SEIRAS results show that two bands corresponding to nas(O=C–O) of HCOO- and nas(C–O) of HCO3 -/CO3 2- appears after the commencement of MOR and varies as a function of potentials. These spectroscopic results are in good agreement with the DFT-based energetics of reaction, suggesting that the MOR mainly proceeds in the following pathway: The early consumption of methanol yields HCOO- as the major product while increasing potentials stimulate further oxidation of adsorbed HCOO* to form HCO3 -/CO3 2-. On the other hand, we show a parallel pathway for the generation of HCO3 -/CO3 2- at high potentials that bypasses the formation of HCOO*. The two main pathways presented in this study are thermodynamically more feasible than the one predominantly reported in literature for MOR on NiOOH. The two former pathways circumvent CHO and/or CO to produce HCO3 -/CO3 2-, whereas the latter involves these species as intermediates. These DFT-based hypotheses are backed up by the spectroscopic evidence that no band associated with CHO and CO can be detected by SEIRAS. This study has the potential to offer invaluable atomic-level insights into MOR on NiOOH as a stepping stone to development of high-performance multi-metallic Ni-based catalysts. Figure 1
33
Tsoncheva, Tanya, Alexandra Mileva, Gloria Issa, et al. "Titania and zirconia binary oxides as catalysts for total oxidation of ethyl acetate and methanol decomposition." Journal of Environmental Chemical Engineering 6, no. 2 (2018): 2540–50. http://dx.doi.org/10.1016/j.jece.2018.03.053.
Full text
34
Dziembaj, R., M. Molenda, L. Chmielarz, M. M. Zaitz, Z. Piwowarska, and A. Rafalska-Łasocha. "Optimization of Cu doped ceria nanoparticles as catalysts for low-temperature methanol and ethylene total oxidation." Catalysis Today 169, no. 1 (2011): 112–17. http://dx.doi.org/10.1016/j.cattod.2010.11.061.
Full text
35
Schallhart, Simon, Pekka Rantala, Eiko Nemitz, et al. "Characterization of total ecosystem-scale biogenic VOC exchange at a Mediterranean oak–hornbeam forest." Atmospheric Chemistry and Physics 16, no. 11 (2016): 7171–94. http://dx.doi.org/10.5194/acp-16-7171-2016.
Full textAbstract:
Abstract. Recently, the number and amount of biogenically emitted volatile organic compounds (VOCs) has been discussed in great detail. Depending on the ecosystem, the published number varies between a dozen and several hundred compounds. We present ecosystem exchange fluxes from a mixed oak–hornbeam forest in the Po Valley, Italy. The fluxes were measured by a proton transfer reaction-time-of-flight (PTR-ToF) mass spectrometer and calculated using the eddy covariance (EC) method. Detectable fluxes were observed for up to 29 compounds, dominated by isoprene, which comprised over 60 % of the total upward flux (on a molar basis). The daily average of the total VOC upward flux was 10.4 nmol m−2 s−1. Methanol had the highest concentration and accounted for the largest downward flux. Methanol seemed to be deposited to dew, as the downward flux happened in the early morning, right after the calculated surface temperature came closest to the calculated dew point temperature.We estimated that up to 30 % of the upward flux of methyl vinyl ketone (MVK) and methacrolein (MACR) originated from atmospheric oxidation of isoprene. A comparison between two methods for the flux detection (manual and automated) was made. Their respective advantages and disadvantages were discussed and the differences in their results shown. Both provide comparable results.
36
Awotedu BF, Omolola TO, Akala AO, Ogunsiji AO, Owoeye EA, and Olaoti-Laaro SO. "Radical Scavenging activity and phytochemical screening of the leaf extract of Synsepalum dulcificum (Schumach. & Thonn.) Daniell." World Journal of Advanced Research and Reviews 10, no. 3 (2021): 069–76. http://dx.doi.org/10.30574/wjarr.2021.10.3.0241.
Full textAbstract:
Antioxidants are chemicals that possess bioactive constituents which usually allow them to fight against free radicals. Antioxidant and phytochemicals properties of the leaves of Synsepalum dulcificum were investigated using ethyl-acetate, ethanol and methanol extracts. 2, 2-diphenyl-picrylhydrazyl (DPPH) scavenging activity, total antioxidant activity, ferric reducing antioxidant power (FRAP), total flavonoid and the total phenolic content was carried out. The phytochemical screening assay was done on the following: Alkaloids, saponin, flavonoids, tannin, anthraquinones, terpenoids, cardiac glycosides, and phlobatannin using the test solvent extracts. The results gotten for antioxidant revealed that methanol gave the highest extract yield (17.4%) while ethyl-acetate extract had the least yield (5.0%). At 250 μg/ml extract concentration, the methanolic extract gave the highest amount with the IC50 values (89.94 μg/ml), followed by ethanol extract (68.20 μg/ml)) while ethyl acetate extract had the least scavenging activity of (39.21 μg/ml), and these were significantly different (P<0.05). Total antioxidant activity (ascorbic acid equivalent) at 250 μg/ml of S. dulcificum ranged from 41.7 AAE in ethyl-acetate extract to 58.98 AAE in methanol extract. Furthermore, ferric reducing antioxidant power (FRAP) of the leaf extracts revealed that at 250 μg/ml extract concentration, methanol extract had the highest (0.29μmolFe2+/g) reduction potential, followed by ethanol extract (0.28μmolFe2+/g) and ethyl-acetate extract (0.26μmolFe2+/g). The total phenolic content of the extracts ranged from 0.02μg/ml TAE–0.09μg/ml TAE at 1000μg/ml extract concentration while the total flavonoid content ranged from 0.32mg/g QE in ethyl-acetate extract to 14.38mg/g QE in methanol extract. This study suggests that S. dulcificum extract exhibit great potential antioxidant ability that could fight against oxidative stress.
37
Montaño-Machado, Vanessa, Livia Angeloni, Pascale Chevallier, et al. "Oxidative Plasma Treatment of Fluorocarbon Surfaces for Blood-Contacting Applications." Materials Science Forum 941 (December 2018): 2528–33. http://dx.doi.org/10.4028/www.scientific.net/msf.941.2528.
Full textAbstract:
Surgical implantation of metallic stents is today a common procedure for restoring narrowed arteries. However, main complications as in-stent restenosis, partial or total thrombosis, inflammation and devices degradation are still a serious clinical concern. The coating of stents with fluorocarbon (CFx) ultrathin films represents a valuable strategy to limit these complications. Moreover, an additional step for the modification of some key surface properties of CFxcoatings could further enhance their blood compatibility. Therefore, the objective of this work was to develop an oxidation process specific to ultrathin CFxcoatings based on a methanol plasma treatment to modulate their biological response. Oxidized and non-oxidized coatings were investigated by XPS, ToF-SIMS, water contact angle, SEM and AFM. Tunable oxidation of the surface of CFxcoatings was obtained by methanol plasma treatment, thus producing an increase of surface wettability, without affecting morphology, roughness and adhesion of the coatings. Blood test results showed an increased hemocompatibility of the oxidized samples, confirming the hypothesis that such treatment can succeed in modulating the blood contact behavior of the CFxoxidized coatings.
38
Mohamed, Ibrahim A., Yaser M. Asal, Sohair A. Darwish, and Islam M. Al-Akraa. "Transesterification of Castrol Oil for Biodiesel Production and Glycerol Electro-oxidation." E3S Web of Conferences 572 (2024): 02002. http://dx.doi.org/10.1051/e3sconf/202457202002.
Full textAbstract:
In this study, transesterification of castor oil with methanol using KOH as catalyst was carried out aiming to produce biodiesel and glycerol. Different factors (oil: alcohol ratio, mixing time, and temperature) affecting the products’ yield were optimized and best sets were obtained. The best condition (90% biodiesel yield) required 5:1 oil: alcohol ratio, 2 h mixing, and 60oC. The physical proper-ties (density, viscosity, pour point, cloud point, water content, total sulphur, gross heating value, and total acid number) of the obtained biodiesel was measured and the Fourier transform infrared (FT-IR) spectroscopy confirmed again the production of both biodiesel and glycerol. Furthermore, the obtained glycerol was further purified, characterized, and its further electro-oxidation was carried out as a fuel cell application.
39
Wang, Qijun, Ya-Wei Zhou, Zhao Jin, Chunguang Chen, Hong Li, and Wen-Bin Cai. "Alternative Aqueous Phase Synthesis of a PtRu/C Electrocatalyst for Direct Methanol Fuel Cells." Catalysts 11, no. 8 (2021): 925. http://dx.doi.org/10.3390/catal11080925.
Full textAbstract:
Carbon-supported PtRu nanoalloy (PtRu/C) is widely used as the anode catalyst for direct methanol fuel cells (DMFC), and an aqueous phase synthesis of PtRu/C is in high demand due to for energy-saving and environmentally-benign considerations, however, it is very challenging to attain stoichiometric reduction, good dispersion and a high alloying degree. Herein, we report a facile aqueous phase approach with dimethylamine borane (DMAB) as the reducing agent to synthesize a PtRu/C(DMAB). TEM, XRD, XPS and ICP-AES characterizations indicate that the structural parameters in the PtRu/C(DMAB) are improved significantly as compared to those obtained in a PtRu/C(NaBH4) and a commercial PtRu/C, contributing to an enhanced electrocatalytic performance. It turns out that the PtRu/C(DMAB) exhibits the highest methanol electro-oxidation (MOR) performance among all of the tested samples, with the peak current up to 1.8 times as much as that of the state-of-the-art commercial PtRu/C, corroborating the highest output power density in comparative DMFC tests. In-situ attenuated total reflection infrared (ATR-IR) spectroscopy correlates the higher methanol electro-oxidation performance of the PtRu/C(DMAB) with its enhanced CO resistance and CO2 generation. This simple aqueous synthetic approach may provide an alternative route for developing efficient anode electrocatalysts of DMFCs.
40
Li, Haiwen, Obaid Ullah Beg, Ahmed Reza Rafie, et al. "Characterization of Green and Yellow Papaya (Carica papaya) for Anti-Diabetic Activity in Liver and Myoblast Cells and Wound-Healing Activity in Fibroblast Cells." Nutrients 15, no. 8 (2023): 1929. http://dx.doi.org/10.3390/nu15081929.
Full textAbstract:
Obesity and diabetes, often characterized as “metabolic syndrome”, have been recognized as two of the most important public health issues worldwide. The objective of the present research was to evaluate green and yellow papaya for anti-oxidation and anti-diabetic properties. Leaves, skin, pulp, and seed samples from papayas were freeze-dried and then extracted in water or 80% methanol. The extracts were used to determine total polyphenolic content and anti-oxidation activities, and to determine biological activities, including glucose uptake, Glut-2 expression, triglyceride reduction, and wound-healing activity. Our data demonstrated that methanol and water extracts of green and yellow papaya have similar concentrations of polyphenols in skin (10–20 mg/g dry powder), leaf (25–30 mg/g dry powder), and pulp (1–3 mg/g dry powder) fractions. However, both methanol and water extracts of seeds from yellow papaya have substantially higher concentrations of polyphenols compared to green papaya. Both water and methanol extracts of yellow papaya exhibited higher anti-oxidation activity compared to green papaya in skin (50–60%), pulp (200–300%), and seeds (10–800%). Old leaves also showed greater anti-oxidation activity (30–40%) compared to new leaves. Pulp extracts from both yellow and green papaya stimulated greater glucose uptake, but only pulp from green papaya stimulated glucose uptake in muscle cells. Similarly, pulp extract stimulated glucose transporter Glut-2 expression in liver cells. The skin, pulp, and seeds of green or yellow papaya showed triglyceride-lowering activity in liver cells by 60–80%, but samples taken from yellow papaya had a more potent effect. Seeds from both green and yellow papaya significantly stimulated the migration of fibroblasts in the wounded area by 2–2.5-fold compared to the untreated control. Consistent with these data, seeds from both green and yellow papaya also significantly stimulated collagen synthesis in fibroblast cells by almost 3-fold. In conclusion, our data indicate that different parts of papaya produce stimulatory effects on glucose uptake, Glut-2 expression, TG reduction, and wound-healing activities. This study concludes that different parts of the papaya can be beneficial for preventing diabetes and diabetes-related wound healing.
41
Usha, B., and K. C. Pushpalatha. "IN VITRO ANTIOXIDANT ACTIVITY AND PHYTOCHEMICAL SCREENING OF LEAF EXTRACTS OF GREWIA HETEROTRICHA MAST." International Journal of Current Pharmaceutical Research 8, no. 4 (2016): 68. http://dx.doi.org/10.22159/ijcpr.2016v8i4.15282.
Full textAbstract:
Objective: To investigate the presence of phytochemical components and to evaluate the in vitro antioxidant activity of pet. ether, chloroform, methanol and aqueous extracts of Grewia heterotricha mast leaves.Methods: The leaves of Grewia heterotricha mast were dried and extracts were prepared using a pet. ether, chloroform, methanol by soxhlet extraction method. The aqueous extract was prepared using distilled water by cold extraction method. The preliminary phytochemical analysis was carried out on aqueous, methanol, chloroform and pet. either leaf extracts of the plant using standard qualitative procedures. The total phenolic content (TPC) was estimated using modified Folin-Ciocalteau method, tannin content by Folin-Denis method and total flavonoids by aluminum chloride method. In vitro, antioxidant activities were evaluated by 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, H2O2 scavenging activity and FRAP assay.Results: The preliminary phytochemical analysis revealed the presence of complex bioactive constituents like phenols, tannins, alkaloids, terpenoids, flavonoids, saponins, steroids, glycosides, coumarins, proteins and carbohydrates. Methanolic extract showed highest total phenolic content (87.58±2.52 mg CE/g) than aqueous extract (78.46±5.36 mg CE/g). Higher tannin content was found in the aqueous extract (148.0±8.96 mg TAE/g). Total flavonoids were highest in chloroform extract (314.9±25.06 mg QE/g) followed by aqueous (242.98±32.42 mg QE/g) and methanolic extract (217.0±18.32 mg QE/g) and lowest in a pet. ether extract (188.86±23.35 mg QE/g). The methanolic extract had shown very significant DPPH radical scavenging activity (IC50 98.95 µg/ml) and H2O2 scavenging activity (IC50110.1µg/ml) compared to the standard ascorbic acid. Higher reducing ability was observed in methanol extract (131.8±11.67 mg AE/g).Conclusion: The results obtained reveal that the leaves of Grewia heterotricha mast have potent antioxidant property. The observed activity may be associated with bioactive components like phenolics, flavonoids present in the leaf extracts and could have greater importance as therapeutic agents in oxidative stress-related degenerative diseases. Further studies are needed in order to purify bioactive compounds responsible for the antioxidant property.
42
Rochard, Guillaume, Eric Genty, Jean-Marc Giraudon, et al. "Synthesis of Gold Nanoparticles over CoAl Mixed Oxide for Ethanol Oxidation Reaction." Molecules 29, no. 10 (2024): 2285. http://dx.doi.org/10.3390/molecules29102285.
Full textAbstract:
Catalytic total oxidation is an effective technique for the treatment of industrial VOCs principally resulting from industrial processes using solvents and usually containing mono-aromatics (BTEX) and oxygenated compounds (acetone, ethanol, butanone). The aim of this work is to deposit gold nanoparticles on CoAl mixed oxide issued from layered double hydroxide (LDH) precursor by using the deposition precipitation (DP) method, which is applied with two modifications, labeled method (A) and method (B), in order to enhance the interaction of the HAuCl4 precursor with the support. Method (A) involves the hydrolysis of the HAuCl4 precursor after addition of the support, while in method (B), the gold precursor is hydrolyzed before adding the support. The two methods were applied using as support the CoAl mixed oxide and the LDH precursor. Samples were characterized by several physical chemical techniques and evaluated for ethanol total oxidation. Method (B) allowed the ethanol oxidation activity to be enhanced for the resulting Au/CoAlOx catalysts thanks to the high surface concentration of Co2+ and improved reducibility at low temperature. The presence of gold permits to minimize the formation of by-products, notably, methanol, allowed for a total oxidation of ethanol at lower temperature than the corresponding support.
43
Dodson, Karen Y., Edna R. Young, and Abdel-Gawad M. Soliman. "Determination of Total Vitamin C in Various Food Matrixes by Liquid Chromatography and Fluorescence Detection." Journal of AOAC INTERNATIONAL 75, no. 5 (1992): 887–90. http://dx.doi.org/10.1093/jaoac/75.5.887.
Full textAbstract:
Abstract A liquid chromatographic method was developed for quantitation of total vitamin C content in various food matrixes. The method includes extraction with 3% mete-phosphoric acid-acetic acid and oxidation of ascorbic acid to dehydroascorbic acid with Norit, followed by reaction with ophenylenediamine to form a fluorescent derivative. The fluorescent derivative is separated on a µBondapak C18 (10 µm) column with methanol-water (55 + 45) and detected fluorometrically. This method is demonstrated to be suitable for several sample matrixes, including complex matrixes of canned corn, potatoes, green beans, potato chips, and cereals. Other products analyzed include infant formula, medical foods, fruit juice, and multivitamin tablets. Recoveries are in the range of 90-108%. Comparison of results with those by the AOAC fluorometric method shows excellent agreement.
44
Ngibad, Khoirul, and Lilla Puji Lestari. "Aktivitas Antioksidan dan Kandungan Fenolik Total Daun Zodia (Evodia suaveolens)." ALCHEMY Jurnal Penelitian Kimia 16, no. 1 (2020): 94. http://dx.doi.org/10.20961/alchemy.16.1.35580.94-109.
Full textAbstract:
<p>Senyawa dengan radikal bebas merupakan senyawa yang mempunyai satu atau lebih elektron tidak berpasangan yang dapat merusak sel dan jaringan jika terakumulasi dalam tubuh manusia. Antioksidan dapat berfungsi untuk menginaktivasi reaksi oksidasi dan mencegah terbentuknya radikal tetapi antioksidan sintetik dapat menyebabkan karsinogen. Oleh karena itu, antioksidan yang terkandung dalam sumber alami perlu diteliti lebih lanjut. Salah satunya adalah tanaman zodia (Evodia suaveolens). Tujuan dari penelitian ini adalah untuk mengetahui nilai aktivitas antioksidan dari ekstrak metanol, etil asetat, dan diklorometana dari daun tanaman zodia yang dinyatakan dengan IC 50 (inhibitory concentration) dan untuk mengetahui kadar fenolik total dari ekstrak daun zodia. Serbuk daun zodia dimaserasi menggunakan tiga pelarut, yaitu metanol, etil asetat, dan diklorometana secara terpisah. Penentuan aktivitas antioksidan dilakukan dengan uji penangkapan radikal DPPH (2,2-difenill-1-pikrilhidrazil) sedangkan penentuan kandungan fenolik total dilakukan menggunakan metode spektrofotometri. Nilai aktivitas antioksidan yang dinyatakan dengan IC 50 dari ekstrak metanol, etil asetat, dan diklorometana dari daun zodia berturut-turut adalah 170, 124, dan 409 ppm. Kadar fenolik total dari ekstrak metanol, etil asetat, dan diklorometana dari daun zodia berturut-turut adalah 0,02430; 0,01183; dan 0,00930 mg GAE/g eks.</p><p> </p><p>Antioxidant Activity and Total Phenolic Content of Zodia Leaves (Evodia suaveolens). The compounds with free radicals are compounds that have one or more unpaired electrons which can damage cells and tissues if they was accumulated in the human body. Antioxidants can act to inactivate oxidation reactions and prevent the formation of radicals but synthetic antioxidants can cause carcinogens. Therefore, antioxidants containing in natural sources need to be investigated. One of them is the zodia (Evodia suaveolens) plant. The purpose of this study was to determine the value of antioxidant activity of methanol, ethyl acetate, and dichloromethane extract from the leaves of the zodia plant in IC 50 (inhibitory concentration) and to determine the total phenolic content of zodia leaf extract. Zodia leaves powder was macerated using three solvents, namely: methanol, ethyl acetate, and dichloromethane, separately. Determination of antioxidant activity was carried out by DPPH (2,2-diphenyl-1-picrilhydrazyl) radical catching test and the determination of total phenolic content was carried out using spectrophotometric methods. The antioxidant activity values expressed by IC 50 from methanol, ethyl acetate, and dichloromethane extracts from zodia leaves were 170, 124, and 409 ppm, respectively. Total phenolic concentrations of methanol, ethyl acetate, and dichloromethane extracts from zodia leaves were 0.02430, 0.01183, and 0.00930 mg GAE/g.</p>
45
Schallhart, S., P. Rantala, E. Nemitz, et al. "Characterization of total ecosystem scale biogenic VOC exchange at a Mediterranean oak-hornbeam forest." Atmospheric Chemistry and Physics Discussions 15, no. 19 (2015): 27627–73. http://dx.doi.org/10.5194/acpd-15-27627-2015.
Full textAbstract:
Abstract. Recently, the number and amount of biogenically emitted volatile organic compounds (VOCs) has been discussed vigorously. Depending on the ecosystem the published number varies between a dozen and several hundred compounds. We present ecosystem exchange fluxes from a mixed oak-hornbeam forest in the Po Valley, Italy. The fluxes were measured by a proton transfer reaction-time-of-flight (PTR-ToF) mass spectrometer and calculated by the eddy covariance (EC) method. Detectable fluxes were observed for twelve compounds, dominated by isoprene, which comprised over 65 % of the total flux emission. The daily average of the total VOC emission was 9.5 nmol m-2 s-1. Methanol had the highest concentration and accounted for the largest deposition. Methanol seemed to be deposited to dew, as the deposition happened in the early morning, right after the calculated surface temperature came closest to the calculated dew point temperature. We estimated that up to 27 % of the upward flux of methyl vinyl ketone (MVK) and methacrolein (MACR) originated from atmospheric oxidation of isoprene. A comparison between two flux detection methods (classical/visual and automated) was made. Their respective advantages and disadvantages were discussed and the differences in their results shown. Both provide comparable results; however we recommend the automated method with a compound filter, which combines the fast analysis and better flux detection, without the overestimation due to double counting.
46
Qian, Li Li, Shu Zhong Wang, and Yan Hui Li. "Review of Supercritical Water Oxidation in Hydrothermal Flames." Advanced Materials Research 908 (March 2014): 239–42. http://dx.doi.org/10.4028/www.scientific.net/amr.908.239.
Full textAbstract:
Supercritical water oxidation in hydrothermal flames is a promising method for the total destruction of refractory compounds because it can overcome corrosion and salt deposition problems. In case of wastewater with a low reaction heat, the use of auxiliary fuels, to increase the reaction heat for the auto thermal operation is necessary. Methanol and isopropyl-alcohol were usually used as fuels. This paper compares the two fuels in hydrothermal flames and reviews the experimental results of salts, acetic acid, dioxins, ammonia, sludge and phenols of naphthalene and toluene. The results show that the destruction process obtains high TOC removals, and phenols are easy to cause soot formation problems. If soot deposition problems can be solved, supercritical water oxidation in hydrothermal flames will have a bright prospect for commercial applications.
47
Moeslinger, T., M. Brunner, I. Volf, and P. G. Spieckermann. "Spectrophotometric determination of ascorbic acid and dehydroascorbic acid." Clinical Chemistry 41, no. 8 (1995): 1177–81. http://dx.doi.org/10.1093/clinchem/41.8.1177.
Full textAbstract:
Abstract We present a method for measuring ascorbic acid in methanol/trichloroacetic acid extracts prepared from human plasma after enzymatic oxidation of ascorbic acid to dehydroascorbic acid by ascorbate oxidase. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of dehydroascorbic acid with phosphate-citrate-methanol buffers. Ascorbic acid was determined as the difference between dehydroascorbic acid and total ascorbic acid content. The detection limit was &lt; 0.5 mumol/L. The calibration curve was linear (r &gt; 0.995) over the range 0-1000 mumol/L. Analytical recovery of ascorbic acid added to plasma was 93-105%. The between-day variance was &lt; 7%. Comparison of the spectrophotometric determination (y) with a chromatographic procedure (x) gave y = 1.02x - 0.653 (Sylx = 3.61) over the range of physiologically relevant concentrations. Total analysis time is &lt; 10 min per sample and allows the simultaneous analysis of multiple samples.
48
Kaminski, Piotr, Izabela Sobczak, Piotr Decyk, et al. "Zeolite MCM-22 Modified with Au and Cu for Catalytic Total Oxidation of Methanol and Carbon Monoxide." Journal of Physical Chemistry C 117, no. 5 (2013): 2147–59. http://dx.doi.org/10.1021/jp310505y.
Full text
49
Sahle-Demessie, E., and Venu Gopal Devulapelli. "Oxidation of methanol and total reduced sulfur compounds with ozone over V2O5/TiO2 catalyst: Effect of humidity." Applied Catalysis A: General 361, no. 1-2 (2009): 72–80. http://dx.doi.org/10.1016/j.apcata.2009.03.035.
Full text
50
Haddouchi, Farah, Tarik Mohammed Chaouche, Riadh Ksouri, and Romain Larbat. "Leafy Stems of Phagnalon saxatile subsp. saxatile from Algeriaas a Source of Chlorogenic Acids and Flavonoids with Antioxidant Activity: Characterization and Quantification Using UPLC-DAD-ESI-MSn." Metabolites 11, no. 5 (2021): 280. http://dx.doi.org/10.3390/metabo11050280.
Full textAbstract:
Phagnalon saxatile subsp. saxatile is a wild species widespread in Algeria which is utilized for medicinal purposes as analgesic and anticholesterolemic. However, information is still scarce regarding its phytochemical content. The objective of this study was to identify and quantify the phenolic compounds from different extracts of its leafy stems. For this purpose, the effects of four extracting solvents were investigated on the content of phenolic compounds and the antioxidant activity of this plant. The extracts prepared with polar solvents (methanol and water) contained higher amounts of phenolic compounds and showed better antioxidant activity than the extracts with apolar solvents (hexane, dichloromethane). The methanolic extract, richest in total phenolic and total flavonoid, had significant antioxidant activity as regarded by DPPH° scavenging capacity (IC50 of 5.5 µg/mL), ABTS+° scavenging capacity (IC50 of 63.8 µg/mL) and inhibition of oxidation of linoleic acid (IC50 of 22.7 µg/mL), when compared to synthetic antioxidants. Chlorogenic acids and several flavonoids were identified and quantified by UPLC-DAD-MSn. The di-O-caffeoylquinic acids isomers were the most concentrated phenolics (25.4 mg/g DW) in the methanolic extract.