Peroxide Yield Research Articles

Oxygen reduction activity of Fe/Co/Ni doped MnOx @ graphene nanohybrid: A comparative study

• Fe, Co, and Ni doped MnO x was grown on NG. • Doped catalysts show better ORR activity than the undoped one. • Doping can tune the Mn valence. • Enhanced activity for doped MnO x owing to increase in Mn valence on doping. We report the electrochemical activity of transition metal ion (Fe, Co and Ni) doped MnO x @ N -graphene (MnO x @NG) hybrid catalysts towards oxygen reduction reaction (ORR). The doped catalysts displayed significantly enhanced electrochemical performance than the undoped one. The Fe doped MnO x @NG exhibited highest positive shift in onset potential (0.93 V vs. RHE), highest electron transfer number (n) (3.87) and lowest peroxide yield (6.35 %) in 0.1 M KOH solution. The Co doped catalyst showed highest current density, which is comparable to that of benchmark 20 wt% Pt/C. The XRD analysis showed that the catalyst samples are poorly crystalline and the doping of either Fe or Co or Ni cation induces formation of Mn 2 O 3 , whereas the undoped catalyst consists of both Mn 2 O 3 and MnOOH. The STEM (scanning transmission electron microscope) micrographs revealed that in all the samples the MnO x nanostructures are well dispersed on NG and the elemental mapping of the doped catalysts showed uniform distribution of dopants. The X-ray photoelectron spectroscopy (XPS) studies revealed that doping of either cation results an increase in the average Mn valency of the host MnO x . The change in crystal structure and corresponding ORR activity has also been investigated with increase in dopant amount for Fe doped samples.

Plasma activated water prepared by different plasma sources: physicochemical properties and decontamination effect on lentils sprouts

The pulsed corona discharge (CD) generated in contact with water and directly in water, and high-power air plasma jet (APJ) were studied for production of plasma activated water (PAW). The changes of physical (pH, redox potential, conductivity, temperature) and chemical (peroxides, nitrites, nitrates concentrations) properties of treated water were investigated. The comparison of CD generated in gas/water interface and underwater configuration in the same system showed that the interaction of reactive oxygen and nitrogen species formed in ambient air in gas/water system induces different chemical processes, leading to lower pH, higher oxidation-reduction potential (ORP) and higher conductivity of PAW than in underwater discharge. High yield of peroxide was observed in both configurations. The PAW prepared by APJ exhibits high concentration of nitrites and nitrates according to supplied energy, and related significant decrease of pH and increase of ORP and conductivity after treatment. The antimicrobial effect of PAW prepared by CD and plasma jet on lentils sprouts was studied in different treatment and washing times. The APJ appears to have great efficacy on water activation resulted in strong decontamination effect. The PAW treated by APJ for 10 min led to bacterial reduction from initial 8.3 to 5.9 and 4.0 log10 CFU g−1 after 10 and 30 min of washing, respectively.

Highly stable N-containing polymer-based Fe/Nx/C electrocatalyst for alkaline anion exchange membrane fuel cell applications

A cost-effective electrocatalyst with high activity and stability was developed. The Fe-Nx and pyridinic-N active sites were embedded in nitrogen-doped mesoporous carbon nanomaterial by carbonization at high temperature. The electrocatalyst exhibited excellent electrochemical performance for the oxygen reduction reaction, with high onset potential and half-wave potential values (Eonset= 1.10 ​V and E1/2 ​= ​0.944 ​V) than 20 ​wt % Pt/C catalyst (1.04 and 0.910 ​V). The mass activity of the Schiff base network (SNW) based SNW-Fe/N/C@800° electrocatalyst (0.64 ​mA ​mg−1 @ 1 ​V) reached about half of the commercial Pt/C electrocatalyst (1.35 ​mA ​mg−1 @ 1 ​V). The electrocatalyst followed the 4-electron transfer mechanism due to very low hydrogen peroxide yield (H2O2 ​< ​1.5%) was obtained. In addition, this electrocatalyst with dual active sites showed high stability during cyclic voltammetry and chronoamperometry measurements. More importantly, the electrocatalyst also demonstrated the power density of 266 ​mW ​cm−2 in the alkaline anions exchange membrane fuel cell (AEMFC) test, indicating its prospective application for fuel cells.

Transition Metal and Nitrogen-Doped Carbide-Derived Carbon/Carbon Nanotube Composites As Cathode Catalysts for Anion-Exchange Membrane Fuel Cells

Energy is an essential part of our lives and causes a significant impact on the environment. As the energy carrier, hydrogen could be a feasible option as it is readily producible and cost-efficient.1 In the transport sector, the proton exchange membrane fuel cells, which use hydrogen as the fuel, are already used, but have issues regarding the usage of high amount of precious metals. However, replacing acidic media with alkaline gives better possibility to use non-precious metal catalysts, especially for the cathodic oxygen reduction reaction (ORR). This suggests that anion exchange membrane fuel cells (AEMFCs) have great promise as future energy devices.2 As non-precious metal catalysts, different transition metal and carbon-based materials have shown great promise.3 Herein, a nanocarbon composite based on carbide-derived carbon/carbon nanotube (CDC/CNT) is used as a support to prepare M−N−C type catalysts. The CDC/CNT composite offers a novel structure containing both micro- and mesopores that is beneficial for the AEMFC application. The composite material is doped with nitrogen and transition metals using pyrolysis at 800 °C in inert atmosphere. As precursors, metal acetates (iron(II) and cobalt(II) acetate) and 1,10-phenantroline are employed. Three M-N-C materials are prepared, namely Fe-N-CDC/CNT, Co-N-CDC/CNT, and bimetallic CoFe-N-CDC/CNT.4 Different physico-chemical characterization methods (SEM-EDX, XPS, XRD, MP-AES, and N2 physisorption) are used to study the catalyst materials, which proved the success of doping (metal content ca. 1 wt%) as well as the feasible micro- and mesoporous structure with defects present. The RRDE method was used for electrochemical testing to study the ORR pathway and activity. In alkaline medium all three catalyst materials exhibit good electrocatalytic activity for the ORR with the peroxide yield depending on the metal additive in order Co > CoFe > Fe. The materials are applied as cathodes in the AEMFC together with ETFE membrane. The MEA with the CoFe-N-CDC/CNT cathode shows the best performance in H2/O2 AEMFC and a very good performance in H2/air AEMFC by obtaining respective peak power densities of 1.12 and 0.80 W cm–2 (Fig. 1). Additionally, the CoFe-N-CDC/CNT exhibited good stability in both AEMFCs. This shows that the M-N-CDC/CNT materials are promising cathode catalysts for the AEMFC application.4 References O. Abe, A. P. I. Popoola, E. Ajenifuja, and O. M. Popoola, Int. J. Hydrogen Energy, 44, 15072-15086 (2019).S. Gottesfeld, D. R. Dekel, M. Page, C. Bae, Y. S. Yan, P. Zelenay, and Y. S. Kim, J. Power Sources, 375, 170-184 (2018).A. Sarapuu, E. Kibena-Põldsepp, M. Borghei, and K. Tammeveski, J. Mater. Chem. A, 6, 776-804 (2018).J. Lilloja, E. Kibena-Põldsepp, A. Sarapuu, J. C. Douglin, M. Käärik, J. Kozlova, P. Paiste, A. Kikas, J. Aruväli, J. Leis, V. Sammelselg, D. R. Dekel, and K. Tammeveski, ACS Catal., 11, 1920-1931 (2021), Figure 1

Heteroatom-Doped Graphites Oxygen Reduction Catalysts for Anion Exchange Membrane Fuel Cells

Catalysts for the oxygen reduction reaction (ORR) are crucial for electrochemical energy conversion and storage devices. The development of active, ultra-low-cost, critical raw materials-free catalysts is vital for the success of the anion exchange membrane fuel cell (AEMFC) technology [1]. In this work, we present metal-free oxygen reduction catalysts based on heteroatoms (I, N, S or B)-doped graphites by a scalable and reproducible one-step planetary ball milling protocol [2]. The distribution and the morphology of these ultra-low cost catalysts are characterized by advanced electron microscopy showing uniform distribution of heteroatoms in the graphite matrix. We have tested the catalysts for ORR in 0.1 M KOH solution in a rotating ring disk electrode (RRDE) and doped-graphites showed enhanced ORR performance relative to the pristine graphite. Among these, the N-graphite exhibiting the highest ORR onset potential of 0.87 V with a low peroxide yield of 15%@0.1 V. Good ORR kinetic (jk,s ) and mass (ik,m ) activities were also obtained. The catalysts also show remarkable stability in both RDE stress and corrosion tests. Finally, we showed good performance in operando H2-O2 AEMFC, reaching ~350 mW cm‒ 2 at 60 oC with a high voltage efficiency. These results encourage further development of metal-free ultra-low-cost and stable catalysts, easily scalable for AEMFC cathode production.

Synthesis, characterization, and application of hollow ceramic microsphere based Pd catalyst for hydrogenation of 2-ethylanthraquinone

Palladium metal has been used extensively in the hydrogenation reactions due to their great affinity towards hydrogen atoms. In the present study, the catalyst preparation attempted with Pd supported Hollow Ceramic Microspheres using wet impregnation method and its use as catalysts is explored in the hydrogenation of 2-ethylanthraquinone studing the effect of the reaction time, temperature, volume of working solution and the catalyst dosages on the conversion of 2-ethylanthraquinone and yield of hydrogen peroxide. The hydrogenation reaction of 2-ethylanthraquinone is the key step in the anthraquinone method for the industrial production of the hydrogen peroxide. The Pd supported catalyst was characterized by XRF, FTIR, and BET to confirm the composition of the prepared catalyst, Pd deposition, and the surface area. The highest catalyst activity was found to be 9.42 ​g/L with the maximum conversion of 96% at 70°C, 0.3 ​MPa. The kinetics of the heterogeneous hydrogenation reaction of 2-ethylanthraquinone with Pd supported on Hollow Ceramic Microspheres as catalyst was also investigated. This paper is in contribution of our earlier publication.

Two adjacent C-terminal mutations enable expression of aryl-alcohol oxidase from Pleurotus eryngii in Pichia pastoris

Fungal aryl-alcohol oxidases (AAOs) are attractive biocatalysts because they selectively oxidize a broad range of aromatic and aliphatic allylic primary alcohols while yielding hydrogen peroxide as the only by-product. However, their use is hampered by challenging and often unsuccessful heterologous expression. Production of PeAAO1 from Pleurotus eryngii ATCC 90787 in Pichia pastoris failed, while PeAAO2 from P. eryngii P34 with an amino acid identity of 99% was expressed at high yields. By successively introducing mutations in PeAAO1 to mimic the sequence of PeAAO2, the double mutant PeAAO1 ER with mutations K583E and Q584R was constructed, that was successfully expressed in P. pastoris. Functional expression was enhanced up to 155 U/l via further replacements D361N (variant NER) or V367A (variant AER). Fed-batch cultivation of recombinant P. pastoris yielded up to 116 mg/l of active variants. Glycosylated PeAAO1 variants demonstrated high stability and catalytic efficiencies similar to PeAAO2. Interestingly, P. pastoris expressing PeAAO1 variant ER contained roughly 13 gene copies but showed similar volumetric activity as NER and AER with one to two gene copies and four times lower mRNA levels. Additional H-bonds and salt bridges introduced by mutations K583E and Q584R might facilitate heterologous expression by enhanced protein folding.Key points• PeAAO1 not expressed in P. pastoris and PeAAO2 well-expressed in Pichia differ at 7 positions.• Expression of PeAAO1 in P. pastoris achieved through mutagenesis based on PeAAO2 sequence.• Combination of K583E and Q584R is essential for expression of PeAAO1 in P. pastoris.

Microbial fuel cell affected the filler pollution accumulation of constructed wetland in the lab-scale and pilot-scale coupling reactors

This study investigated electrochemical performance, the filler pollution and microorganism community in constructed wetland (CW) and constructed wetland-microbial fuel cell coupling reactor (CW-MFC). CW-MFC could purify the wastewater and affect the filler pollution in different scales (lab-scale and pilot-scale), filler (gravel and activated carbon) and feeding modes (intermittent and continuous influent) reactors. Our study found that the best electrochemical performance (106 mW/m2 of power density) at the lab-scale level was obtained in I-G-CW-MFC (I = intermittent flow condition, G = gravel). The highest yield of hydrogen peroxide (2.91 mg/L) was detected in I-AC-CW-MFC (AC = activated carbon). At the pilot-scale (316 L effective volume), the specific surface area of P-CW-MFC-B (B = the bottom of the reactor) (928.4 ± 12.0 m2/g) was larger than that of the P-CW-B (810.6 ± 4.0 m2/g), and P-CW-NS (819.0 ± 12.5 m2/g) was larger than P-CW-MFC-NS (749.5 ± 2.1 m2/g), which indicated that the filler pollution contamination of the CW-MFC was lighter than that of CW. The biomass accumulation of filler in CW-MFC coupling system (0.048 ng/g) was less than that of CW (0.021 ng/g), which further demonstrated that the CW-MFC coupling system could reduce filler pollution to a certain extent. The intermittent pilot-scale CW-MFC coupling system could change the distribution of pollutants in the filler and reduce the accumulation of pollutants. These results demonstrated that MFC had a significant effect on the filler pollution accumulation of constructed wetland in the pilot-scale system, which may offer opportunities for clogging reduction of filler in CW.

Nanocomposite of platinum and prussian blue: A highly active and stable electrocatalyst towards oxygen reduction reaction in acidic media

Deployment of proton exchange membrane fuel cells (PEMFCs) are of vital importance for the mitigation of fossil energy shortage and environment pollution. A significant amount of Pt on cathode is highly needed to accelerate the process of sluggish oxygen reduction reaction (ORR) and maintains a stable long-term performance. During ORR, the yield of undesirable hydrogen peroxide through a two-electron pathway not only decreases outer power but also weakens the long-term stability. Herein, Pt-prussian blue (PB) composite, featuring around structure, is firstly proposed and facilely fabricated via electrostatic self-assembly strategy. Pt1PB0.25/C shows 50% higher activity than commercial Pt/C, rationally ascribed to modulated electronic structure and higher selectivity towards four-electron pathway. Moreover, in contrast with the striking 38% loss in mass activity for Pt/C after accelerated degradation tests (ADTs), Pt1PB0.25/C shows only a 15% decrease possibly due to the elimination of hydrogen oxide and the anchor interaction between Pt and PB. The employment of PB with a synergy role paves an efficient way for the fabrication of brand-new Pt-based catalysts with high activity and stability.

Molecule-confined modification of graphitic C3N4 to design mesopore-dominated Fe-N-C hybrid electrocatalyst for oxygen reduction reaction

To design inexpensive carbon catalysts and enhance their oxygen reduction reaction (ORR) activity is critical for developing efficient energy-conversion systems. In this work, a novel Fe-N-C hybrid electrocatalyst with carbon nanolayers-encapsulated Fe3O4 nanoparticles is synthesized successfully by utilizing the molecular-level confinement of graphitic C3N4 structures via hemin biomaterial. Benefiting from the Fe-N structure prevalent on the carbon nanosheets and large mesopore-dominated specific surface area, the synthesized catalyst under optimized conditions shows excellent electrocatalytic performance for ORR with an EORR at 1.08 V versus reversible hydrogen electrode (RHE) and an E1/2 at 0.87 V vs. RHE, and outstanding long-term stability, which is superior to commercial Pt/C catalysts (EORR at 1.04 V versus RHE and E1/2 at 0.84 V versus RHE). Moreover, the low hydrogen peroxide yield (<11%) and average electron transfer number (~3.8) indicate a four-electron ORR pathway. Besides, the maximum power density of the home-made Zn-air battery using the obtained catalyst is 97.6 mW cm−2. This work provides a practical route for the synthesis of cheap and efficient ORR electrocatalysts in metal-air battery systems.

Regulating Electrocatalytic Oxygen Reduction Activity of a Metal Coordination Polymer via d-π Conjugation.

Non-noble transition metal complexes have attracted growing interest as efficient electrocatalysts for oxygen reduction reaction (ORR) while their activities still lack rational and effective regulation. Herein, we propose a d-π conjugation strategy for rough and fine tuning of ORR activity of TM-BTA (TM=Mn/Fe/Co/Ni/Cu, BTA=1,2,4,5-benzenetetramine) coordination polymers. By first-principle calculations, we elucidate that the strong d-π conjugation elevates the dxz /dyz orbitals of TM centers to enhance intermediate adsorption and strengthens the electronic modulation effect from substitute groups on ligands. Based on this strategy, Co-TABQ (tetramino benzoquinone) is found to approach the top of ORR activity volcano. The synthesized Co-TABQ with atomically distributed Co on carbon nanotubes exhibits a half-wave potential of 0.85 V and a specific current of 127 mA mgmetal -1 at 0.8 V, outperforming the benchmark Pt/C. The high activity, low peroxide yield, and considerable durability of Co-BTA and Co-TABQ promise their application in oxygen electrocatalysis. This study provides mechanistic insight into the rational design of transition metal complex catalysts.

Regulating Electrocatalytic Oxygen Reduction Activity of a Metal Coordination Polymer via d–π Conjugation

AbstractNon‐noble transition metal complexes have attracted growing interest as efficient electrocatalysts for oxygen reduction reaction (ORR) while their activities still lack rational and effective regulation. Herein, we propose a d–π conjugation strategy for rough and fine tuning of ORR activity of TM‐BTA (TM=Mn/Fe/Co/Ni/Cu, BTA=1,2,4,5‐benzenetetramine) coordination polymers. By first‐principle calculations, we elucidate that the strong d–π conjugation elevates the dxz/dyz orbitals of TM centers to enhance intermediate adsorption and strengthens the electronic modulation effect from substitute groups on ligands. Based on this strategy, Co‐TABQ (tetramino benzoquinone) is found to approach the top of ORR activity volcano. The synthesized Co‐TABQ with atomically distributed Co on carbon nanotubes exhibits a half‐wave potential of 0.85 V and a specific current of 127 mA mgmetal−1 at 0.8 V, outperforming the benchmark Pt/C. The high activity, low peroxide yield, and considerable durability of Co‐BTA and Co‐TABQ promise their application in oxygen electrocatalysis. This study provides mechanistic insight into the rational design of transition metal complex catalysts.

Porous Co/NPC@TiO2/TiN composite: Facile preparation and excellent catalytic activity for the oxygen reduction reaction

It is very important to develop efficient noble-metal-free catalysts for oxygen reduction reaction (ORR) to promote the application of commercial fuel cells. Inspired by this idea, ZIF 67 was selected as template to synthesize hierarchical porous TiO2/TiN coated Co/N co-doped carbon (Co/NPC) composite after being coated with tetrabutyl titanate (TBOT). The catalytic activity, stability and corrosion resistance of the optimal porous Co/NPC@TiO2/TiN composite towards ORR were improved by TiO2/TiN shell layer and carbon nanotubes. The results showed that the limit diffusion current (5.32 mA cm−2, at 0.1 V vs. RHE), onset potential (0.87 V) and half-wave potential (0.754 V) of Co/NPC@TiO2/TiN-2 were closed to the corresponding values of 20 wt% Pt/C (5.53 mA cm−2, 0.93 V and 0.773 V), respectively. The electron transfer number was 3.90–3.95 at a potential of 0.1–1.05 V, indicating a 4e- pathway for ORR and the yield of by-product hydrogen peroxide was below 6%. Additionally, Co/NPC@TiO2/TiN-2 also possessed good methanol tolerance and high cycle stability in alkaline media. This work provides a practical method to design ORR catalysts with distinguished performances.

Effects of LET on oxygen-dependent and-independent generation of hydrogen peroxide in water irradiated by carbon-ion beams

Linear energy transfer (LET) dependence of yields of O2-dependent and O2-independent hydrogen peroxide (H2O2) in water irradiated by ionizing radiation was investigated. The radiation-induced hydroxyl radical (•OH) generation in an aqueous solution was reported to occur in two different localization densities, the milli-molar (relatively sparse) and/or molar (markedly-dense) levels. In the milli-molar-level •OH generation atmosphere, •OH generated at a molecular distance of ∼7 nm are likely unable to interact. However, in the molar-level •OH generation atmosphere, several •OH were generated with a molecular distance of 1 nm or less, and two •OH can react to directly make H2O2. An aliquot of ultra-pure water was irradiated by 290-MeV/nucleon carbon-ion beams at the Heavy-Ion Medical Accelerator in Chiba (HIMAC, NIRS/QST, Chiba, Japan). Irradiation experiments were performed under aerobic or hypoxic (<0.5% oxygen) conditions, and several LET conditions (13, 20, 40, 60, 80, or >100 keV/μm). H2O2 generation in irradiated samples was estimated by three methods. The amount of H2O2 generated per dose was estimated and compared. O2-independent H2O2 generation, i.e. H2O2 generation under hypoxic conditions, increased with increasing LET. On the other hand, the O2-dependent H2O2 generation, i.e. subtraction of H2O2 generation under hypoxic conditions from H2O2 generation under aerobic conditions, decreased with increasing LET. This suggests that the markedly-dense •OH generation is positively correlated with LET. High-LET beams generate H2O2 in an oxygen-independent manner.

Nitrogen-doped graphene-like carbon from bio-waste as efficient low-cost electrocatalyst for fuel cell application

The development of metal-free carbon-based catalysts for alkaline fuel cells has been the subject of current interest, because of the low cost and improving fuel cell efficiency. Particularly, nitrogen-doped carbon shows prominent results. Here, we show an oxygen reduction reaction (ORR) activity of nitrogen-doped graphene-like carbon materials (N-GLC) prepared by heating bagasse-derived carbon and melamine in a 1:15 ratio. The N-GLC catalyst displays excellent electro-catalytic activity towards the ORR with an onset potential of 0.92 V vs. reversible hydrogen electrode (RHE) in alkaline media (0.1 M KOH). Moreover, the half-wave (E1/2) potential 0.83 V is almost the same compared to Pt-C (40 wt%) catalyst and the diffusion limiting current of 4 mA cm–2. The rotating ring disc experiment showed a four-electron pathway (n = 3.65) with the moderate peroxide ( $${{\rm HO}}^{-}_{2}$$ ) yield. Due to its promising ORR activity and long-term electrochemical stability, N-GLC catalyst is used in alkaline anion exchange membrane fuel cell (AEMFC) as a single cell, about 6 mW cm–2 peak power density was achieved at the load current density of ~20 mA cm–2. So the N-GLC can be a cheap alternative ORR catalyst for AEMFC applications.

Non-thermal plasma-induced DMPO-OH yields hydrogen peroxide

Recent developments in electronics have enabled the medical applications of non-thermal plasma (NTP), which elicits reactive oxygen species (ROS) and reactive nitrogen species (RNS), such as hydroxyl radical (●OH), hydrogen peroxide (H2O2), singlet oxygen (1O2), superoxide (O2●-), ozone, and nitric oxide at near-physiological temperatures. In preclinical studies or human clinical trials, NTP promotes blood coagulation, eradication of bacterial, viral and biofilm-related infections, wound healing, and cancer cell death. To elucidate the solution-phase biological effects of NTP in the presence of biocompatible reducing agents, we employed electron paramagnetic resonance (EPR) spectroscopy to quantify ●OH using a spin-trapping probe, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO); 1O2 using a fluorescent probe; and O2●- and H2O2 using luminescent probes in the presence of thiols or tempol. NTP-induced ●OH was significantly scavenged by dithiothreitol (DTT), reduced glutathione (GSH), and oxidized glutathione (GSSG) in 2 or 5 mM DMPO. NTP-induced O2●- was significantly scavenged by 10 μM DTT and GSH, while 1O2 was not efficiently scavenged by these compounds. GSSG degraded H2O2 more effectively than GSH and DTT, suggesting that the disulfide bonds reacted with H2O2. In the presence of 1–50 mM DMPO, NTP-induced H2O2 quantities were unchanged. The inhibitory effect of tempol concentration (50 and 100 μM) on H2O2 production was observed in 1 and 10 mM DMPO, whereas it became ineffective in 50 mM DMPO. Furthermore, DMPO-OH did not interact with tempol. These results suggest that DMPO and tempol react competitively with O2●-. Further studies are warranted to elucidate the interaction between NTP-induced ROS and biomolecules.

Pharmaceutical Excipients Enhance Iron-Dependent Photo-Degradation in Pharmaceutical Buffers by near UV and Visible Light: Tyrosine Modification by Reactions of the Antioxidant Methionine in Citrate Buffer.

To evaluate the effect of excipients, including sugars and amino acids, on photo-degradation reactions in pharmaceutical buffers induced by near UV and visible light. Solutions of citrate or acetate buffers, containing 1 or 50μM Fe3+, the model peptides methionine enkephalin (MEn), leucine enkephalin (LEn) or proctolin peptide (ProP), in the presence of commonly used amino acids or sugars, were photo-irradiated with near UV or visible light. The oxidation products were analyzed by reverse-phase HPLC and HPLC-MS/MS. The sugars mannitol, sucrose and trehalose, and the amino acids Arg, Lys, and His significantly promote the oxidation of peptide Met to peptide Met sulfoxide. These excipients do not increase the yields of hydrogen peroxide, suggesting that other oxidants such as peroxyl radicals are responsible for the oxidation of peptide Met. The addition of free Met reduces the oxidation of peptide Met, but, in citrate buffer, causes the addition of Met oxidation products to Tyr residues of the target peptides. Commonly used excipients enhance the light-induced oxidation of amino acids in model peptides.

CHEMICAL COMPOSITION OF SEEDS AND SEED OIL OF Afraegle paniculata (Rutaceae)

Afraegle paniculata (Schumach. &amp; Thonn.) Engl. commonly known as Nigerian powder-flask is a plant of rutaceae family found in West Africa from Senegal to Nigeria. The chemical composition of seeds and seed oil of Afraegle paniculata were evaluated in this study. The seed oil was obtained by soxhlet extraction using n-hexane. Chemical composition analyses involved proximate, mineral element, physicochemical and phytochemical. The percentage mean value of the proximate analysis revealed that the seeds contained 28.81±0.02 % crude fat, 25.03±0.12 % crude protein, 10.90±0.03 % moisture, 3.11±0.01 % ash, 25.19±0.02 % crude fibre and 6.96±0.14 % carbohydrate. The mineral element analysis result showed that potassium (114.87 mg/l) was the predominant mineral element followed by magnesium (47.20±0.037 mg/l) and sodium (45.37±0.53 mg/l). Other minerals present were calcium (2.12±0.014 mg/l), iron (1.12±0.028 mg/l), copper (0.41±0.002 mg/l), zinc (0.39±0.094 mg/l) and manganese (0.29±0.005 mg/l). The oil was liquid at room temperature and golden yellow in appearance. The recorded pH, acid, peroxide, iodine, saponification, ester and oil yield values were 3.94, 1.29 mgKOH/g, 17.57 meq/kg, 42.24 mgI2/100g, 203.76 mgKOH/g, 202.47 mgKOH/g, 40.77 % w/w respectively . The presence of alkaloids, saponins, terpenoids, steroids and anthraquinone were evident in the phytochemical screening of the seed oil. Nutritional profile of A. paniculata seed could offer a scientific basis for use of the seeds and oils both in human diet and some commercial products. Keywords: Afraegle paniculata, proximate, mineral elements, physicochemical and phytochemical.

Theory-Driven Design of Electrocatalysts for the Two-Electron Oxygen Reduction Reaction Based on Dispersed Metal Phthalocyanines

Theory-Driven Design of Electrocatalysts for the Two-Electron Oxygen Reduction Reaction Based on Dispersed Metal Phthalocyanines

Effect of longitudinal magnetic field to the linear particle-beam track on yields of hydroxyl radical and hydrogen peroxide in water

Effect of longitudinal magnetic field to the linear particle-beam track on yields of hydroxyl radical and hydrogen peroxide in water