• Journal of Hydrogen and New Energy
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• v.28 no.6
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• pp.669-674
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• 2017

In this study, the novel electrochemical and colorimetric analysis methods are suggested to estimate the degree of phosphoric acid ion poisoning on Pt based catalyst surface and to confirm the possibility of replacing the expensive and long time consumed conventional methods. As the ways, the electrochemical half cell tests such as cyclic voltammetry (CV) and linear sweep voltammetry (LSV) are used and the change in chemical behavior by absorption of the phosphoric acid ion on Pt based catalyst surface and hydrogen peroxide decomposition reaction are successfully recognized by colorimetric measurements. Conclusively, it is proved that the new methods show superior sensitivity for identifying the degree of phosphoric acid poisoned on Pt based catalyst.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2979-2983
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• 2009

Nanowires of polytetrakis(o-aminophenyl)porphyrin (PTAPPNW) were fabricated by electrochemical polymerization with the cyclic voltammetric method in anodic aluminum oxide (AAO) membranes. The glassy carbon electrode (GCE) modified by PTAPPNW, single-walled carbon nanotubes (SWNT) and Nafion as a binder was investigated with voltammetric methods in a phosphate buffer saline (PBS) solution at pH 7.4. The PTAPPNW + SWNT + Nafion/GCE exhibited strongly enhanced voltammetric and amperometric sensitivity towards hydrogen peroxide ($H_2O_2$), which shortened the response time and enhanced the sensitivity for $H_2O_2$ determination at an applied potential of 0.0 V by amperometric method. The PTAPPNW + SWNT + Nafion/GCE can be used to monitor $H_2O_2$ at very low concentrations in biological pH as an efficient electrochemical $H_2O_2$ sensor.

• Journal of the Korean Chemical Society
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• v.67 no.5
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• pp.339-347
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• 2023

In this study, a nanocomposite of multi-walled carbon nanotubes@poly(p-phenylenediamine)-Prussian blue (MWCNTs@PpPD-PB) was synthesized and employed for the electrochemical detection of hydrogen peroxide (H₂O₂). A straightforward approach was utilized to prepare an electrochemical H₂O₂ sensor using a MWCNTs@PpPD-PB modified glassy carbon electrode, and its electrochemical behavior was investigated through techniques such as electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The modified electrode displayed a favorable electrocatalytic response towards the reduction of H₂O₂ in an acidic solution. The developed sensor exhibited linearity in the concentration range of 0.005 mM to 2.225 mM for H₂O₂, with high sensitivity (583.6 ㎂ mM^-1cm^-2) and a low detection limit (0.95 ㎛, S/N = 3) at an applied potential of +0.15 V (vs. Ag/AgCl). Additionally, the sensor demonstrated excellent selectivity, reproducibility, and stability. Moreover, successful detection of H₂O₂ was achieved in real samples.

• Biomolecules & Therapeutics
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• v.15 no.1
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• pp.65-72
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• 2007

Flax seed(Linseed, Linum usitatissimum L.) and its oil, a richest source of alpha-linolenic acid(ALA)(${\omega}-3$), contain saturated fatty acids, neurotoxic cyanogen glycosides and immuno-suppressive cyclic-nonapeptides. Present paper describes the development of two chemical processes, Process-A and -B, to remove saturated fatty acids and to destroy cyclic nonapeptides and cyanogen glycosides from flax seed oil. Process-A consists of three major steps, i.e., extraction of fatty acid mixture by alkaline saponification, removal of saturated fatty acid by urea-complexation, and triglyceride reconstruction of unsaturated fatty acid via fatty acyl-chloride activation using oxalyl chloride. Process-B consists of preparation of fatty acid ethyl ester by transesterification, elimination of saturated fatty acid ester by urea-complexation, and reconstruction of triglyceride by interesterification with glycerol-triacetate (triacetin). The destruction of lipophilic cyclic nonapeptide during saponification or transesterification processes could be demonstrated indirectly by the disappearance of antibacterial activity of bacitracin, an analogous cyclic-decapeptide. The cyanogen glycosides were found only in the dregs after hexane extraction, but not in the flax seed oil. The reconstructed triglyceride of flax seed oil, obtained by these two different pathways after elimination of saturated fatty acid and toxic components, showed agreeable properties as edible oil in terms of taste, acid value, iodine and peroxide value, glycerine content, and antioxidant activity.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.3 s.116
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• pp.13-22
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• 2006

The analogs of cyclic hydroxamic acids containing N-OH group have been proposed to play effective laccase-mediators in kraft pulp bleaching with laccase/mediator system. The existing mediators (NHA, 1-HBT, VA), the best laccase-mediators reported so far, and selected several analogs of cyclic hydroxamic acids were evaluated as a laccase-mediator for kraft pulp bleaching. It was found that NHA was the most effective mediator for the Trychophyton sp. LKY-7 laccase (TrL) in kraft pulp bleaching with TrL/mediator system, increasing about 10% ISO of brightness and decreasing about 2.8 of kappa number after alkaline-peroxide bleaching. Of the cyclic hydroxamic acidstested, the NHP.1(N-hydroxypyridone analog) was shown to enable TrL to effectively degrade lignin in kraft pulp bleaching, demonstrating approximately similar effect with that of NHA. However, the effect of substituent patterns of cyclic hydroxamic acid analogs in kraft pulp bleaching was not observed. The inhibitions of NHA and NHP.1 on TrL were not exhibited in TrL/mediator system. As a new mediator for TrL, NHP.1 was considered to be able to use in kraft pulp bleaching with TrL/mediator system.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.447-454
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• 2017

A new amperometric biosensor has been developed for the detection of hydrogen peroxide ($H_2O_2$). The sensor was fabricated through the one-step deposition of a biocomposite layer onto a glassy carbon electrode at neutral pH. The biocomposite, as a $H_2O_2$ sensing element, was prepared by the electrochemical deposition of a homogeneous mixture of graphene oxide, aniline, and horseradish peroxidase. The experimental results clearly demonstrated of that the sensor possessed high electrocatalytic activity and responded to $H_2O_2$ with a stable and rapid manners. Scanning electron microscopy, cyclic voltammetry, and amperometry were performed to optimize the characteristics of the sensor and to evaluate its sensing chemistry. The sensor exhibited a linear response to $H_2O_2$ in the range of 10 to $500{\mu}M$ concentrations, and its detection limit was calculated to be $1.3{\mu}M$. The proposed sensing-chemistry strategy and the sensor format were simple, cost-effective, and feasible for analysis of "food-grade $H_2O_2$" in food samples.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.1033-1037
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• 2008

A copper cyclam-type complex was successfully immobilized onto mesoporous silica SBA-16. Characterization by NIR spectroscopy and TGA analysis confirmed that copper cyclam complex is immobilized onto mesoporous SBA-16. The Cu(II)-Cyclam-SBA-16 was proven to be a good catalyst for oxidation reaction of cyclohexene with conversion up to 77.8% after 13 h reaction and providing a high selectivity to cyclohexenol and 3-hydroperoxycyclohex-1-ene. The results suggest that the copper species play a major role as catalyst via reversible redox cycles as proven by cyclic voltammetry analysis.

• Elastomers and Composites
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• v.55 no.1
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• pp.51-58
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• 2020

In this study, the thermal oxidation of raw natural rubber (NR) was investigated under controlled conditions by optical image and fourier transform infrared (FT-IR) analysis. The thermal oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at 80℃ under low humidity conditions to completely exclude moisture and restrict light oxidation. Images of the thin film of raw NR were obtained before and after thermal oxidation. FT-IR absorption spectra were measured in the transmission mode at different thermal exposure times. The thermal oxidation of NR was examined by the changes in the absorption peaks at 3449, 1736, 1447, 1377, 1242, 1072, and 833 cm^-1, which corresponded to a hydroxyl group (-OH), a carbonyl group (-C=O) from an aldehyde and a ketone, a methylene group (-CH₂-), a methyl group (-CH₃), a carbon-oxygen single bond (-C-O) from an epoxide, a carbon-oxygen bond (-C-O) from an ether, an alcohol, a peroxide, or a cyclic peroxide, and a cis-methine group (cis-CCH₃=CH-), respectively. In the initial stage of thermal oxidation, two different types of free radicals were produced quickly and randomly by the homolytic cleavage of a double bond and allylic hydrogen abstraction. Aldehydes and ketones were formed from chain scissions of the double bonds and alcohols were produced from allylic hydrogen abstraction at the methylene or methyl groups. Two reactions seemed to proceed competitively with each other. At a later stage, oxidative crosslinks seemed to dominate through the combination of free radicals such as an allyl radical (CH=CHCH₂·), alkoxy radical (RO·), and peroxy radical (ROO·) and the reaction of a hydroperoxide (-ROOH) with a double bond. The image obtained after thermal oxidation showed hardening without cracks. Based on these observations, a plausible two-step mechanism was suggested for chain hardening caused by the thermal oxidation.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.3
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• pp.315-324
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• 2016

Human cardiac fibroblasts (HCFs) have various voltage-dependent $K^+$ channels (VDKCs) that can induce apoptosis. Hydrogen peroxide ($H_2O_2$) modulates VDKCs and induces oxidative stress, which is the main contributor to cardiac injury and cardiac remodeling. We investigated whether $H_2O_2$ could modulate VDKCs in HCFs and induce cell injury through this process. In whole-cell mode patch-clamp recordings, application of $H_2O_2$ stimulated $Ca^{2+}-activated$ $K^+$ ($K_{Ca}$) currents but not delayed rectifier $K^+$ or transient outward $K^+$ currents, all of which are VDKCs. $H_2O_2-stimulated$ $K_{Ca}$ currents were blocked by iberiotoxin (IbTX, a large conductance $K_{Ca}$ blocker). The $H_2O_2-stimulating$ effect on large-conductance $K_{Ca}$ ($BK_{Ca}$) currents was also blocked by KT5823 (a protein kinase G inhibitor) and 1 H-[1, 2, 4] oxadiazolo-[4, 3-a] quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor). In addition, 8-bromo-cyclic guanosine 3', 5'-monophosphate (8-Br-cGMP) stimulated $BK_{Ca}$ currents. In contrast, KT5720 and H-89 (protein kinase A inhibitors) did not block the $H_2O_2-stimulating$ effect on $BK_{Ca}$ currents. Using RT-PCR and western blot analysis, three subtypes of $K_{Ca}$ channels were detected in HCFs: $BK_{Ca}$ channels, small-conductance $K_{Ca}$ ($SK_{Ca}$) channels, and intermediate-conductance $K_{Ca}$ ($IK_{Ca}$) channels. In the annexin V/propidium iodide assay, apoptotic changes in HCFs increased in response to $H_2O_2$, but IbTX decreased $H_2O_2$-induced apoptosis. These data suggest that among the VDKCs of HCFs, $H_2O_2$ only enhances $BK_{Ca}$ currents through the protein kinase G pathway but not the protein kinase A pathway, and is involved in cell injury through $BK_{Ca}$ channels.

• Journal of the East Asian Society of Dietary Life
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• v.20 no.5
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• pp.735-742
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• 2010

Biogenic amines are synthesized by microbial decarboxylation for the putrefaction or fermentation of foods containing protein. Although biogenic amines such as histamine, tyramine, and putrescine are required for many physiological functions in humans and animals, consumption of high amounts of biogenic amines can cause toxicological effects, including serious gastrointestinal, cutaneous, hemodynamic, and neurological symptoms. In this study, a novel amperometric biosensor wasdeveloped to detect biogenic amines. The biosensor consisted of a working electrode, a reference electrode, a counter electrode, an enzyme reactor with immobilized diamine oxidase, an injector, a peristaltic pump and a potentiostat. A working electrode was fabricated with a glassy carbon electrode (GCE) by coating functionalized multi-walled carbon nanotubes (MWCNT-$NH_2$) and by electrodepositing Prussian blue (PB) to enhance electrical conductivity. A sensor system with PB/MWCNT-$NH_2$/GCE showed linearity in the range of $0.5 {\mu}M{\sim}100 {\mu}M$ hydrogen peroxide with a detection limit of $0.5 {\mu}M$. The responses for tyramine, 2-phenylethylamine, and tryptamine were 95%, 75%, and 70% compared to that of histamine, respectively. These results imply that the biosensor system can be applied to the quantitative measurement of biogenic amines.