Range Of Peroxide Concentrations Research Articles

Determination of the peroxide anion radical in water by the chemiluminescent method

Introduction. The necessity of the analysis of peroxide anion radicals in the aqueous medium as the main element performing a special role in the management of internal processes in the body is substantiated. 
 Goals and objectives of the study. Creation of methodological support for the determination of a superoxide anion radical in drinking waters, providing metrological characteristics of parameterization of its systemic homeostatic action in a biologically significant concentration range. The task of the study was to find a method and optimal conditions for determining the concentration of peroxide anion radical in drinking waters that differ in their electrochemical parameters.
 Materials and methods. As an analytical instrument for measuring ultra-low concentrations of hydrogen peroxide in water (more than 0.1 µg/l), a kinetic chemiluminescent analyzer was used (liquid chemiluminescent analyzer “LIK Universal”, TU 9443-001-42844321-03).) Parametrization of the ratio of anion-radical and free molecular forms of hydrogen peroxide in the specified range of its concentrations in water was carried out by HPLC. A capillary cryophysical method based on the selection of chains of self-similar aqueous associates was used to estimate the dimensional parameters of the associates of peroxide anion radicals.
 Results. The dependence of the integral chemiluminescence intensity on the concentration of superoxide anion radicals in water was established to be linear only in the range of peroxide concentrations from 0 to 40 µg/l. At the same time, the time to reach the maximum intensity of the glow depends on the concentration of the peroxide anion radical in water. By studying the dimensional parameters of associates of peroxide anion radicals from the content of hydrogen peroxide in water, it was found that in the range of ultra-low concentrations they practically do not change for a sufficiently long time, which is due to the stability of the isomerism of water molecules in this concentration range.
 Limitations. The objects, composition, quantitative limits and conditions for measuring anion radical peroxide using this technique apply to drinking water, the quality and control methods of which are regulated by regulatory documents of the international community.
 Conclusion. A method for estimating the content of peroxide-anion radical in water based on the use of a kinetic chemiluminescence method with a sensitivity 
 of about 10–1 µg/l in small volumes of water (50–200 µl) has been developed, which has sufficient accuracy and reproducibility for practical purposes.

ЗАЩИТНЫЕ СВОЙСТВА ЭРИТРОЦИТОВ ПРИ ГЕМОЛИЗЕ И ИХ РЕГУЛЯЦИЯ ОКИСЛИТЕЛЯМИ

Hydrogen peroxide, which is formed during cellular respiration and the action of physicochemical factors, is an important participant in intracellular regulatory processes. A moderate increase in the concentration of hydrogen peroxide activates the mechanisms associated with protection and adaptation, and at a high level of the oxidant, damage to cellular structures is observed. The work shows that under the action of hydrogen peroxide in micromolar concentrations, an increase in the structural stability of membranes and a decrease in the proportion of hemolyzed erythrocytes are observed upon destruction by hypochlorous acid, silver nanoparticles, and silver nitrate. A method for quantitative assessment of the regulation of the erythrocyte protective properties by hydrogen peroxide during hemolysis by various factors is proposed. It has been shown that the range of hydrogen peroxide concentrations at which an increase in the proportion of non-hemolyzed cells (the region of hormesis) is observed differs for various factors leading to destruction. Based on the developed mathematical model of cell destruction under the action of a damaging factor and hormesis dependences of the erythrocyte response to the action of hydrogen peroxide, the parameters characterizing the regulation of cellular adaptation processes were calculated. The proposed method for analyzing the protective properties of cells makes it possible to compare the adaptive properties of erythrocytes and determine the optimal conditions for their regulation by external factors.

Detection of Hydrogen Peroxide in Liquid and Vapors Using Titanium(IV)-Based Test Strips and Low-Cost Hardware.

Titanium(IV) solutions are known to detect hydrogen peroxide in solutions by a colorimetric method. Xplosafe’s XploSens PS commercial titanium(IV)-based peroxide detection test strips are used to detect hydrogen peroxide in liquids. The use of these test strips as gas-phase detectors for peroxides was tested using low-cost hardware. The exposure of these strips to hydrogen peroxide liquid or gas leads to the development of an intense yellow color. For liquids, a digital single-lens reflex camera was used to quantify the color change using standardized solutions containing between 50 and 500 ppm peroxide by mass. Analysis of the images with color separation can provide a more quantitative determination than visual comparison to a color chart. For hydrogen peroxide gas, an inexpensive web camera and a tungsten lamp were used to measure the reflected light intensity as a function of exposure from a test strip held in a custom cell. First-order behavior in the color change with time was observed during the exposure to peroxide vapor over a range of peroxide concentrations from 2 and 30 ppm by volume. For a 1-min measurement, the gas-phase detection limit is estimated to be 1 ppm. A 0.01 ppm detection limit can be obtained with a 1-h exposure time. Titanium(IV)-based peroxide detection test strips are sensitive enough to work as a gas-phase hydrogen peroxide detector.

A Stochastic Characterization of Hydrogen Peroxide-Induced Regulated Cell Death in Microcystis aeruginosa.

Regulated cell death (RCD) encompasses the activation of cellular pathways that initiate and execute a self-dismissal process. RCD occur over a range of stressors doses that overcome pro-survival cellular pathways, while higher doses cause excessive damage leading to passive accidental cell death (ACD). Hydrogen peroxide (HP) has been proposed as a potential tool to control harmful cyanobacterial blooms, given its capacity to remove cyanobacterial cells and oxidize cyanotoxins. HP is a source of hydroxyl radicals and is expected to induce RCD only within a limited range of concentrations. This property makes this compound very useful to better understand stress-driven RCD. In this work, we analyzed cell death in microcystin-producing Microcystis aeruginosa by means of a stochastic dose response model using a wide range of HP concentrations (0, 0.29, 1.76, 3.67, 7.35, 14.70, and 29.5 mM). We used flow cytometry and unsupervised classification to study cell viability and characterize transitional cell death phenotypes after exposing cells to HP for 48 and 72 h. Non-linear regression was used to fit experimental data to a logistic cumulative distribution function (cdf) and calculate the half maximal effective concentration (EC50). The EC50 of M. aeruginosa exposed to HP were 3.77 ± 0.26 mM and 4.26 ± 0.22 mM at 48 and 72 h, respectively. The derivative of cdf (probability density function; pdf) provided theoretical and practical demonstration that EC50 is the minimal dose required to cause RCD in 50% of cells, therefore maximizing the probability of RCD occurrence. 1.76 mM HP lead to an antioxidant stress response characterized by increased reactive oxygen species (ROS) levels and HP decomposition activity. The exposure of 3.67 mM HP induced a dose-related transition in cell death phenotype, and produced several morphological changes (a less dense stroma, distortion of the cell membrane, partial disintegration of thylakoids, extensive cytoplasmic vacuolation and highly condensed chromatin). The EC50 and the stochastic cdf and pdf together with the multidimensional transitional phenotypic analysis of single cells contribute to further characterize cell death pathways in cyanobacteria.

Two-dimensional phononic crystal sensor for volumetric detection of hydrogen peroxide (H2O2) in liquids

In this work, a novel design of a highly sensitive two-dimensional fluid/fluid phononic crystal sensor for sensing hydrogen peroxide (H 2 O 2 ) concentrations up to 75.5% in water is presented. The transmission spectra of the phononic crystal sensor is calculated based on the finite element method (FEM). The host matrix is made from mercury and the inclusions are filled with water. H 2 O 2 with different concentrations have been added in a cavity inside the phononic crystal design. Different resonant modes related to each H 2 O 2 concentration were localized in the center of the phononic band gap. It is predicted that the central frequency of this resonant mode changes as the concentration of the H 2 O 2 alters. The sensor showed high performance and quality factor versus a wide range of H 2 O 2 concentrations. The sensitivity reached up the value of 426 Hz for each 1% change in H 2 O 2 concentration. Also, we obtained a quality factor with the value of 1612 and a figure of merit with the value of 2488. Thereby this sensor can be used as a highly sensitive biosensor for hydrogenates, acidity and all components such as glucose and uric acid in the blood. Finally, obtained simulation results revealed that the proposed H 2 O 2 sensor can be considered as a competitive, prospective, flexible and commercial device for detecting and distinguishing H 2 O 2 concentrations with high efficiency. • A highly sensitive two-dimensional phononic crystal sensor is proposed to distinguish hydrogen peroxide -water mixtures. • The sensor structure from mercury as a host matrix and water inclusions. • The proposed sensor showed high performance and quality factor versus a wide range of hydrogen peroxide concentrations. • The sensor has a sensitivity of the value 426 Hz for each 1% change in H 2 O 2 concentration.

Novel manganese(II)-based metal-organic gels: synthesis, characterization and application to chemiluminescent sensing of hydrogen peroxide and glucose.

A metal-organic gel (MOG) was synthesized that is composed of manganese(II) as the central ion and 1,10-phenanthroline-2,9-dicarboxylic acid as the ligand. The resulting MOG exhibits excellent activity for catalyzing the chemiluminescence (CL) of the luminol/hydrogen peroxide system. The CL system was characterized by CL spectra, UV-vis absorption spectra and by studying potential interferences by common radical scavengers. The CL reaction was exploited in a new scheme for the determination of hydrogen peroxide. CL intensity increases linearly in the 0.4μM ~ 3mM hydrogen peroxide concentration range, and the limit of detection (LOD) is 0.12μM. The method was extended to an enzymatic assay for glucose by using glucose oxidase and by measurement of the enzymatically formed hydrogen peroxide. The assay works in the 0.2μM ~ 3mM glucose concentration range, and the LOD is 0.08μM. Graphical abstract Schematic representation of the synthesized Mn-containing MOGs catalyzing luminol-hydrogen peroxide chemiluminescent reaction, which can be used to establish a new CL method for the detection of hydrogen peroxide and glucose.

Aggregation of Gold Nanoparticles Caused in Two Different Ways Involved in 4-Mercaptophenylboronic Acidand Hydrogen Peroxide.

The difference in gold nanoparticle (AuNPs) aggregation caused by different mixing orders of AuNPs, 4-mercaptophenylboronic acid (4-MPBA), and hydrogen peroxide (H2O2) has been scarcely reported. We have found that the color change of a ((4-MPBA + AuNPs) + H2O2) mixture caused by H2O2 is more sensitive than that of a ((4-MPBA + H2O2) + AuNPs) mixture. For the former mixture, the color changes obviously with H2O2 concentrations in the range of 0~0.025%. However, for the latter mixture, the corresponding H2O2 concentration is in the range of 0~1.93%. The mechanisms on the color change originating from the aggregation of AuNPs occurring in the two mixtures were investigated in detail. For the ((4-MPBA + H2O2) + AuNPs) mixture, free 4-MPBA is oxidized by H2O2 to form bis(4-hydroxyphenyl) disulfide (BHPD) and peroxoboric acid. However, for the ((4-MPBA+AuNPs) + H2O2) mixture, immobilized 4-MPBA is oxidized by H2O2 to form 4-hydroxythiophenol (4-HTP) and boric acid. The decrease in charge on the surface of AuNPs caused by BHPD, which has alarger steric hindrance, is poorer than that caused by -4-HTP, and this is mainly responsible for the difference in the aggregation of AuNPs in the two mixtures. The formation of boric acid and peroxoboric acid in the reaction between 4-MPBA and H2O2 can alter the pH of the medium, and the effect of the pH change on the aggregation of AuNPs should not be ignored. These findings not only offer a new strategy in colorimetric assays to expand the detection range of hydrogen peroxide concentrations but also assist in deepening the understanding of the aggregation of citrate-capped AuNPs involved in 4-MPBA and H2O2, as well as in developing other probes.

FeNi3/SiO2 magnetic nanocomposite as an efficient and recyclable heterogeneous fenton-like catalyst for the oxidation of metronidazole in neutral environments: Adsorption and degradation studies

In present research, firstly, FeNi3/SiO2 magnetic Nano composite was synthesized and then used in the presence of H2O2 as a heterogeneous Fenton-like catalytic process for removing the antibiotic metronidazole. The morphology and the other properties of the synthesized nanocomposite were characterized by XRD, FESEM, TEM, FTIR and VSM techniques. The present study was conducted in batches (with pH values of 3, 5, 7, 9, and 11), in nanocomposite doses (ranging 0.005–0.1 g/L), in metronidazole concentrations of 10–30 mg/L, and a hydrogen peroxide concentration range of 50–200 mg/L. The results were read by the device (Spectrophotometer UV/Vis T80 +) and showed that by increasing the dose of Nano catalyst synthesized from 0.005 to 0.1 g/L, the percentage of pollutant removal increased from 40.96 to 80.29% in 180 min. Also with increase of the concentration of metronidazole from 10 to 30 mg/L the percentage of deletion decreased markedly (95.32–63.14%). with the elevation of H2O2 concentration from 50 to 150 mg/L, the percentage of metronidazole degradation increased from 64.73% to 80.29%. This issue can be attributed to the point that with the elevation of H2O2 concentration from 50 to 150 mg/L, the concentration of hydroxyl radicals increased as did the metronidazole removal percentage. Owing to hydroxyl radical scavenging and the recombination of the hydroxyl radical, however, with the elevation of H2O2 concentration to 200 mg/L, the removal percentage dropped to 03/75%. Furthermore, the kinetics of the degradation rate of metronidazole followed the pseudo-first-order equation (R2 > 0.9) and the constant rate of degradation of this reaction was obtained as 0.0044 1/min. In this study, the efficiency and the reusability of the synthesized magnetic nanocomposite were examined in the removal of metronidazole. The findings suggest that after 6 cycles of performance of this Nano catalyst, had no significant decrease so that the removal efficiency from the first cycle to the last cycle showed a decrease of about 7.99%. The present research showed that the heterogeneous Fenton-like catalytic process of FeNi3/SiO2/H2O2 had very good efficiency in removing metronidazole antibiotic contamination from aqueous solutions.

Patterned gold electrode prepared from optical discs display largely enhanced electrochemical sensitivity as exemplified in a sensor for hydrogen peroxide

Gold film electrodes (Au-FE) with distinct nanostructured patterns were prepared from polycarbonate (PC) substrates and investigated with respect to their analytical sensitivity. The recordable (R) and read-only memory (ROM) discs, respectively, yield PC substrates with grooves (stripe pattern) or pits (indented pattern). The Au-FEs were characterized in terms of surface morphology and surface patterns, and it was found that the surface area of all Au-FEs does not significantly differ (by 0.2 to 7.4 %) compared to electrode with flat surfaces. However, the electrical signal of indented patterns is larger by 32 to 213 % when directly compared to stripe-patterned Au-FEs (at the same scale of groove and pit). An Au-FE prepared from a polycarbonate sheet from a Blu-ray disc read only memory (BD-ROM) as substrate displayed the best electrochemical performance towards reductive sensing of H2O2. The respective calibration plot, acquired at a working potential of −0.1 V vs. Ag/AgCl, covers the 0 to 10 mM hydrogen peroxide concentration range. The sensitivity is as high as 3.11 μA∙mM−1∙cm−2 which is larger by a factor of 28 compared to flat gold electrodes, and the detection limit (at a signal-to-noise ratio of 3) is 6 μM. Therefore, the results confirm that the indented nanopattern on the Au-FE significantly increases the efficiency of electrochemical detection. Conceivably, the surface patterns and structures may be designed in order to tune sensitivity with respect to future applications of Au-FEs in diagnostics, agriculture, and environmental monitoring.

Isolation of lactic acid bacteria exhibiting high scavenging activity for environmental hydrogen peroxide from fermented foods and its two scavenging enzymes for hydrogen peroxide.

To obtain lactic acid bacteria that scavenge environmental hydrogen peroxide, we developed a specialized enrichment medium and successfully isolated Pediococcus pentosaceus Be1 strain from a fermented food. This strain showed vigorous environmental hydrogen peroxide scavenging activity over a wide range of hydrogen peroxide concentrations. High Mn-catalase and NADH peroxidase activities were found in the cell-free extract of the P. pentosaceus Be1 strain, and these two hydrogen peroxide scavenging enzymes were purified from the cell-free extract of the strain. Mn-catalase has been purified from several microorganisms by several researchers, and the NADH peroxidase was first purified from the original strain in this report. After cloning the genes of the Mn-catalase and the NADH peroxidase, the deduced amino acid sequences were compared with those of known related enzymes.

Amperometric mediatorless hydrogen peroxide sensor with horseradish peroxidase encapsulated in peptide nanotubes

A mediatorless sensor with horseradish peroxidase (HRP) enzymes encapsulated inside peptide nanotubes (PNTs) has been proposed for amperometric detection of hydrogen peroxide. PNTs not only encapsulate the enzymes to retain their activity and stability, but also can provide direct electron transfer between an electrode and the electroactive sites of HRP without mediators. Experimental results were compared with hydroquinone (HQ)-mediated electron transfer results. The PNT/HRP sensor produced a current signal comparable to the HQ/HRP sensor in the entire range of hydrogen peroxide concentrations (0–60mM). The amperometric signal was the greatest when PNT and HQ were used together. The current signal of the PNT/HQ/HRP system increased rapidly with the hydrogen peroxide concentration while the PNT/HRP and HQ/HRP systems showed a similar increase in the rate of current with hydrogen peroxide. The current-H2O2 concentration relations of the tested systems were analyzed using the Michaelis–Menten type equation. Using PNTs as immobilizing agents for enzymes may circumvent the drawbacks of chemical mediators such as HQ that may interfere with the redox reactions and may cause toxicity problems to enzymes.

DNA-Damaging Effects of Dental Bleaching Agents

We studied DNA-damaging effects of dental bleaching systems containing hydrogen peroxide and/or carbamide peroxide by the "comet assay" (alkaline version). Dental bleaching systems in a hydrogen peroxide concentration range from 0.03 to 30 mM produced a genotoxic effect on isolated HeLa cells in vitro comparable with the effects of pharmacopoeial hydrogen peroxide or urea peroxide. Catalase protected the cells against products containing hydrogen peroxide and had no effect on the genotoxicity of samples containing carbamide peroxide.

Flow injection determination of hydrogen peroxide using catalytic effect of cobalt(II) ion on a dye formation reaction

A novel flow injection photometric method was developed for the determination of hydrogen peroxide in rainwater. This method is based on a cobalt(II)-catalyzed oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline (DAOS) as a modified Trinder's reagent to produce intensely colored dye (λmax=530nm) in the presence of hydrogen peroxide at pH 8.4. In this method, 1,2-dihydroxy-3,5-benzenedisulfonic acid (Tiron) acted as an activator for the cobalt(II)-catalyzed reaction and effectively increased the peak height for hydrogen peroxide. The linear calibration graphs were obtained in the hydrogen peroxide concentration range 5×10−8 to 2.2×10−6moldm−3 at a sampling rate of 20h−1. The relative standard deviations for ten determinations of 2.2×10−6 and 2×10−7moldm−3 hydrogen peroxide were 1.1% and 3.7%, respectively. The proposed method was successfully applied to the determination of hydrogen peroxide in rainwater samples and the analytical results agreed fairly well with the results obtained by different two reference methods; peroxidase method and hydrogen peroxide electrode method.

Determination of hydrogen peroxide concentration using a handheld Raman spectrometer: Detection of an explosives precursor

It has been shown that a handheld Raman spectrometer can be used to determine hydrogen peroxide concentration in aqueous solutions in seconds. To allow quantitative analysis, the aqueous peroxide samples were mixed 50/50 (v/v) with a 4mol/dm(3) sodium perchlorate solution which acted as the internal standard. Standard calibration using relative peak heights of the strongest perchlorate (932cm(-1)) and peroxide bands (876cm(-1)) gave an average error of 1.43% for samples in the range 5-30% peroxide. PLS regression of the same data set gave an average error of 0.98%. In addition, the concentrations of the samples were estimated by searching spectra against a library of standard spectra prepared using the same range of peroxide concentrations at 5% increments and with the same perchlorate internal standard. It was found that the library searching method classified all the test samples correctly, matching either the spectra of the same concentration, if they were present, or matching to the closest concentration if an exact match was not possible. This method thus provides a very rapid technique to allow determination of hydrogen peroxide concentrations in the field, for example at suspected improvised explosives manufacturing sites, without complex calibration procedures.

Nanomolar detection of hydrogen peroxide at a new polynuclear cluster of tin pentacyanonitrosylferrate nanoparticle-modified carbon ceramic electrode

This work describes a new electrochemical sensor for hydrogen peroxide based on tin pentacyanonitrosylferrate (SnPCNF)-modified carbon ceramic electrode (CCE). The modified electrode was constructed by using a sol–gel technique involving two steps: construction of CCE containing metallic tin (Sn) powder and then electrochemical creation of SnPCNF film on the surface of CCE. The modified electrode was characterized by energy-dispersive X-ray, Fourier transform infrared, scanning electron microscopy, and cyclic voltammetry (CV) techniques. The charge transfer coefficient ( α) and charge transfer rate constant ( k s) for the modifying film were calculated. The electrocatalytic activity of the modified electrode toward the reduction of hydrogen peroxide was studied by CV and chronoamperometry. A linear calibration curve was obtained over the hydrogen peroxide concentration range of 0.5 to 69.4 μM using a hydrodynamic amperometric technique. The limit of detection (for a signal-to-noise ratio of 3) and sensitivity were found to be 92 nM and 0.89 μA/μM, respectively. Furthermore, the diffusion coefficient of hydrogen peroxide ( D) and catalytic rate constant ( k cat) were calculated.

Protein Disulfide Bond Formation in the Cytoplasm during Oxidative Stress

The majority of disulfide-linked cytosolic proteins are thought to be enzymes that transiently form disulfide bonds while catalyzing oxidation-reduction (redox) processes. Recent evidence indicates that reactive oxygen species can act as signaling molecules by promoting the formation of disulfide bonds within or between select redox-sensitive proteins. However, few studies have attempted to examine global changes in disulfide bond formation following reactive oxygen species exposure. Here we isolate and identify disulfide-bonded proteins (DSBP) in a mammalian neuronal cell line (HT22) exposed to various oxidative insults by sequential nonreducing/reducing two-dimensional SDS-PAGE combined with mass spectrometry. By using this strategy, several known cytosolic DSBP, such as peroxiredoxins, thioredoxin reductase, nucleoside-diphosphate kinase, and ribonucleotide-diphosphate reductase, were identified. Unexpectedly, a large number of previously unknown DSBP were also found, including those involved in molecular chaperoning, translation, glycolysis, cytoskeletal structure, cell growth, and signal transduction. Treatment of cells with a wide range of hydrogen peroxide concentrations either promoted or inhibited disulfide bonding of select DSBP in a concentration-dependent manner. Decreasing the ratio of reduced to oxidized glutathione also promoted select disulfide bond formation within proteins from cytoplasmic extracts. In addition, an epitope-tagged version of the molecular chaperone HSP70 forms mixed disulfides with both beta4-spectrin and adenomatous polyposis coli protein in the cytosol. Our findings indicate that disulfide bond formation within families of cytoplasmic proteins is dependent on the nature of the oxidative insult and may provide a common mechanism used to control multiple physiological processes.

Oxygen-17 NMR study of aqueous peroxotungstates.

Aqueous peroxotungstates have been studied from pH 0.5 to 9.0, over a range of peroxide concentrations. Although equilibria are not always established, many anions can be identified by 17O NMR because the ratio of deltaO(W anion)/deltaO(known Mo anion) is consistently 79 +/- 3%. They are [WO3(HO2)]-; [WO(OH)(O2)2]-; [WO(OH2)(O2)2]0; [W2O3(O2)4]2-; [W2O3(OH)(O2)4]3-; [W4O12(O2)2]4-; [W7O23(O2)]6- and [W7O22(O2)2]6-. Their pKa values, where measurable, are about 2 units lower than the corresponding peroxomolybdates, e.g. 0.0 for [WO(OH2)(O2)2]0 and 8.0 for [W2O3(O2)4]2-. Other peroxotungstate species are also present but can only be broadly identified. These include Keggin structures with relatively low peroxo content, and a very unsymmetrical anion appearing at pH ca. 7 that bears no obvious structural relationship to any species previously reported. The main product from the reaction of powdered W metal with 30% aqueous peroxide is provisionally identified as the symmetrical anion [W6O13(OH)2(OH2)2(O2)5]2-, although other minor species are also formed, probably having fewer peroxo substituents.

Degradation of carbon tetrachloride by modified Fenton’s reagent

The degradation of tetrachloromethane (carbon tetrachloride—CT) by modified Fenton’s reagent (catalyzed hydrogen peroxide) was investigated using a range of hydrogen peroxide concentrations and 1 mM iron(III) catalyst. The documented reactive species in modified Fenton’s reactions, hydroxyl radical (OH ), is not reactive with CT, yet CT degradation was observed in the Fenton’s reactions and was confirmed by chloride generation. Because CT is not reactive with OH , a reductive mechanism which may involve superoxide radical anion is proposed for CT degradation in modified Fenton’s systems. Scavenging of reductants by excess chloroform prevented CT degradation, confirming a reductive mechanism. Similar to CT, three other oxidized aliphatic compounds, hexachloroethane, bromotrichloromethane, and tetranitromethane, were also degraded by modified Fenton’s reagent. The results show that modified Fenton’s reactions act through a reductive mechanism to degrade compounds that are not reactive with OH , which broadens the scope of this process for hazardous waste treatment and remediation.

Electrochemical preparation, characterization and application of electrodes modified with hybrid hexacyanoferrates of copper and cobalt

Hybrid copper–cobalt hexacyanoferrate (CuCoHCF) films were electrodeposited on a platinum electrode or a glassy carbon electrode by cyclic voltammetry and characterized by electrochemistry, XRD, ICP–AES and XPS. The results indicated that CuCoHCF was a substitution-type hybrid hexacyanoferrate. With the increase of Cu 2+ content in the deposition solution, the Cu 2+ content in the films increased correspondingly, while the lattice constant of the films decreased gradually. The CuCoHCF modified platinum electrode exhibited stable electrochemical responses in a wide pH range of 4–10 and permeability for monovalent cations in the order of K +>Li +>Na +>NH 4 +, both of which are different from those of the respective single component copper or cobalt hexacyanoferrates. XPS gave direct evidence that the iron element existed in the form of Fe(III) in oxidized films and was reduced to Fe(II) during X-ray scanning. K + was incorporated into and excluded from CuCoHCF films to maintain electrical neutrality during the reduction and oxidation process, respectively. The CuCoHCF modified glassy carbon electrode exhibited obvious electrocatalytic activity towards both reduction and oxidation of hydrogen peroxide. When a cathodic catalytic current was used, the sensor exhibited a linear response in a hydrogen peroxide concentration range of 2.3×10 −3–8.1×10 −7 M with a detection limit of 6.6×10 −8 M. The hydrogen peroxide sensor showed excellent stability and anti-interference ability towards oxygen and other easily oxidized compounds due to a low applied potential of 0.02 V, which is a great merit for further application in the field of biosensors.

HYBRID COPPER–COBALT HEXACYANOFERRATE FILMS MODIFIED GLASSY CARBON ELECTRODE AS AN ELECTROCHEMICAL SENSOR FOR HYDROGEN PEROXIDE

ABSTRACT Hybrid copper–cobalt hexacyanoferrate, a new member of hexacyanoferrate family, was electrodeposited on a glassy carbon electrode and used as an electrochemical sensor for hydrogen peroxide. The modified electrode could electrocatalyze both reduction and oxidation of hydrogen peroxide in neutral solution. When cathodic catalytic current was used, the sensor exhibited a linear response in hydrogen peroxide concentration range of 2.3 × 10−3 ~8.1 × 10−7 mol/L and the detection limit of 6.6 × 10−8 mol/L. The sensor exhibited high electrocatalysis efficiency towards the reduction of hydrogen peroxide and had good stability and excellent anti-interference ability due to the low applied potential of 0.02 V.