Synthesis of peroxyacetic acid using in situ electrogenerated hydrogen peroxide on gas diffusion electrode

Peroxyacetic acid (PAA) has been first prepared from acetic acid in the presence of solid superacid, Nafion-H, as a catalyst at ambient temperature and atmospheric pressure using gas diffusion electrode (GDE) as an oxygen cathode. Hydrogen peroxide was electrogenerated by the reduction of oxygen on the GDE and PAA could be produced by a redox reaction between electrogenerated hydrogen peroxide and acetic acid. The continuous operation was carried out to examine the electrolysis performance of the present electrolysis system. The results demonstrate that the system can be continuously operated over one month with the production of PAA of ca. 1.9–2.3 mM.     

Effect of trialkylammonium salts and current density on the electrosynthesis of hydrogen peroxide from oxygen in a gas-diffusion electrode in acid solutions

The influence exerted by the nature of cation of a supporting electrolyte and by the current density on the electroreduction of oxygen to hydrogen peroxide in acid K₂SO₄ solutions (pH 0.9–1.4) in gas-diffusion hydrophobized carbon black electrodes with varied electrolyte porosity was studied.     

Selective peracetic acid determination in the presence of hydrogen peroxide using a label free enzymatic method based on catalase

Peracetic acid (PAA) is selectively determined in the presence of hydrogen peroxide (H₂O₂) by using the self-indicating UV–Vis molecular absorption properties of catalase. The PAA reacts with the protein giving an intermediate (Cat-I) which is reduced back by the aminoacid core surrounding the hemegroup. Since the original form of the enzyme and the Cat-I have different UV–Vis absorption properties, the absorbance changes can be used for PAA determination. The H₂O₂/catalase reaction is extremely fast so that neither Cat-I compound nor kinetic interferences are observed. The method permits PAA determination in the 5 × 10⁻⁷ to 1.5 × 10⁻⁵ M range, the reproducibility being between 1% and 10%. Using this method, PAA has been successfully determined in water samples treated with commercial PAA/H₂O₂ biocides. A theoretical study has also been carried out for obtaining a mathematical model able to analytically describe the process.     

Pilot laboratory electrolyzer for electrosynthesis of hydrogen peroxide in acid and alkaline solutions

Results of a preparative electrosynthesis of hydrogen peroxide by cathodic reduction of oxygen in a carbon black gas-diffusion electrode in acid and alkaline electrolyte solutions in a versatile pilot laboratory three-chamber electrolyzer are presented.     

Calmagite dye oxidation using in situ generated hydrogen peroxide catalysed by manganese(II) ions

Hydrogen peroxide (H(2)O(2)) generated from the manganese(II) catalysed reduction of dioxygen has been shown to efficiently oxidize Calmagite (3-hydroxy-4-(2-hydroxy-5-methylphenylazo)naphthalene-1-sulfonic acid) in aqueous solution at pH 8.0 and 20 +/- 1 degrees C with de-protonated Tiron (1,2-dihydroxybenzene-3,5-disulfonate, disodium salt) acting as an essential co-ligand.     

Selective signaling of peracetic acid over hydrogen peroxide by desulfurization of an anthracene-thioamide

Selective signaling of peracetic acid by desulfurization of a thioamide was investigated. A thioamide derivative of anthracene 1 was efficiently desulfurized by peracetic acid to the corresponding amide 2, which resulted in a pronounced turn-on type fluorescent signaling. Signaling was not affected by the presence of another important oxidant hydrogen peroxide thereby providing selective signaling of the peracetic acid from its frequent contaminant hydrogen peroxide. Anthracene-thioamide 1 also provided selectivity for peracetic acid over commonly encountered metal ions and anions. The chemical transformation was confirmed by ¹H NMR, ¹³C NMR, and fluorescence measurements.     

Hydrogen peroxide and peracetic acid determination in waste water using a reversible reagentless biosensor

During the reversible reaction between peroxidase (HRP) and peroxides, several peroxidase intermediate species, showing different molecular absorption spectra, are formed which can be used for their determination. On this basis, a reversible reagentless optical biosensor based on HRP for hydrogen peroxide and peracetic acid determinations has been developed. The biosensor (which can be used for at least 3 months and/or more than 200 measurements) is prepared by HRP entrapment in a polyacrylamide gel matrix. A mathematical model (in which optical, kinetic and transport aspects are considered) relating the measured absorbance with the analyte concentration is also presented. Both peroxides show similar responses in the sensor film. Under the recommended working conditions, the biosensor shows linear response ranges from 6 × 10⁻⁷ to 1.0 × 10⁻⁴ M using FIA mode, and from 2 × 10⁻⁷ to 1.5 × 10⁻⁵ M using continuous mode for both peroxides; the precision, expressed as R.S.D., is about 4%. This biosensor has been applied for peroxide determination in waste water samples previously treated with peroxides.     

Non-enzymatic detection of hydrogen peroxide using a functionalized three-dimensional graphene electrode

A novel three-dimensional (3D) electrochemical sensor was developed for highly sensitive detection of hydrogen peroxide (H₂O₂). Monolithic and macroporous graphene foam grown by chemical vapor deposition (CVD) served as the electrode scaffold. Using in-situ polymerized polydopamine as the linker, the 3D electrode was functionalized with thionine molecules which can efficiently mediate the reduction of H₂O₂ at close proximity to the electrode surface. Such stable non-enzymatic sensor is able to detect H₂O₂ with a wide linear range (0.4 to 660 μM), high sensitivity (169.7 μA mM^− 1), low detection limit (80 nM), and fast response (reaching 95% of the steady current within 3 s). Furthermore, this sensor was used for real-time detection of dynamic release of H₂O₂ from live cancer cells in response to a pro-inflammatory stimulant.     

The effect of carbon black mixture composition on the structural and electrochemical characteristics of gas diffusion electrodes for electrosynthesis of hydrogen peroxide

Gas-diffusion electrodes containing polytetrafluoroethylene, acetylene black A437E and its mixtures with two types of furnace black (P702 and P268E) with different size of particles are studied. The electrode capacitance, the average diameter and volume of pores and their surface area are investigated as a function of the electrode composition. The kinetic characteristics of electrodes in the oxygen electroreduction are assessed. The slope of polarization curves in Tafel coordinates and the transfer coefficient value are shown to be virtually independent of the electrode composition. The preparative synthesis of Н₂О₂ is carried out.     

An EPR study on wastewater disinfection by peracetic acid,hydrogen peroxide and UV irradiation

EPR spectroscopy was applied to obtain qualitative and quantitative information on the radicals produced in disinfection processes of wastewater for agricultural reuse. The DEPMPO spin trap was employed to detect hydroxyl and carbon-centered short living radicals in two different peracetic acid solutions and a hydrogen peroxide solution used for water disinfection either in the absence or in the presence of UV-C irradiation. Moreover, three different kinds of water (wastewater, demineralized water, distilled water) were analysed in order to assess the contribution of Fenton reactions to the radical production. The spectroscopic results were discussed in relation to the efficiency of the different oxidizing agents and UV irradiation in wastewater disinfection evaluated as Escherichia Coli, Faecal and Total Coliforms inactivation.     

Controlled-potential electrosynthesis of glucosaminic acid from glucosamine at a gold electrode

The electrocatalytic oxidation of d-glucosamine (2-amino-2-deoxy-d-glucose) in alkaline and neutral solutions was examined using a carbon felt electrode modified with 2 nm core sized gold nanoparticles (Au_2 nm nanoparticles) and a gold plate electrode. The electrocatalytic voltammetric oxidation curves of d-glucosamine were obtained in both solutions. The voltammetric responses for the electrocatalytic oxidation at a Au_2 nm nanoparticle-modified electrode in both alkaline and neutral solutions were almost the same to those at a gold plate electrode. The oxidized product was identified to be d-glucosaminic acid (2-amino-2-deoxy- d-gluconic acid) generated by the 2-electron oxidation product of d-glucosamine by electrospray ionization time-of-flight mass spectra (ESI TOF-MS). The HPLC results also indicated that the oxidation product was d-glucosaminic acid.The controlled-potential electrolysis of d-glucosamine was performed at the Au_2 nm nanoparticle-modified carbon felt electrodes in both alkaline and neutral solutions. In the alkaline solution, at a potential of −0.2 V, d-glucosaminic acid was formed with a current efficiency of 100%. In the neutral solution, electrolysis at 0.4 V on d-glucosaminic acid was obtained with current efficiencies of 70%.     

Spectrophotometric determination of enzymatically generated hydrogen peroxide using Sol-Gel immobilized horseradish peroxidase

Peroxidase entrapment in different Sol-Gel matrices was successful. The enzyme did not show a decrease in activity for at least 2 months as well as storage at room temperature and dry condition for periods exceeding 3 weeks. It was evident that the enzymatic activity was a function in the type of the alkoxysilane precursor. In addition, the optimum temperature which resulted in maximum enzymatic activity was also dependent on the type of Sol-Gel matrix. Excellent results were obtained for the determination of glucose in serum samples using soluble glucose oxidase in conjunction with the Sol-Gel entrapped peroxidase. The enzymatically produced hydrogen peroxide is oxidized by the entrapped peroxidase yielding oxygen which oxidizes the faint blue variamine blue into the intensely violet colored species (the molar absorptivity is about 1.8 x 10(4) 1 mol(-1) cm(-1)). The characteristics of this chromogenic system as well as optimized conditions for its use in the spectrophotometric determination of enzymatically generated hydrogen peroxide were investigated. Excellent agreement between the results obtained by the proposed method and the widely used standard method, utilizing a commercial reagents kit, was always observed.     

Hydroxyl radicals electrochemically generated in situ on a boron-doped diamond electrode

The hydroxyl radicals electrochemically generated in situ on a boron-doped diamond (BDD) electrode have been investigated for the first time in different electrolyte media, over the whole pH range between 1 and 11. A more extensive characterisation of BDD electrochemical properties is very important to understand the reactivity of organic compounds towards electrochemical oxidation on the BDD electrode, which is related to their interaction with adsorbed hydroxyl radicals due to water oxidation on the electrode surface. An oxidation peak corresponding to the transfer of one electron and one proton was observed in pH <9 electrolytes, associated with the water discharge process and electrochemical generation of hydroxyl radicals, which can interact and enhance the electro-oxidation of organic compounds. In pH >9 electrolytes the electrochemical generation of hydroxyl radicals was not observed; ammonia buffer electrolyte gave a pH-independent peak corresponding to the ammonia oxidation reaction. Additionally, for most pH values studied, a few small peaks associated with the electrochemical interaction between non-diamond carbon species on the doped diamond electrode surface and the electrolyte were also seen, which suggests that the doped diamond is relatively unreactive, but not completely inert, and the electrogenerated hydroxyl radicals play a role as mediator in the oxidation of organics.     

Nanomolar amperometric sensing of hydrogen peroxide using a graphite pencil electrode modified with palladium nanoparticles

We report on a simple and rapid method for the preparation of a disposable palladium nanoparticle-modified graphite pencil electrode (PdNP-GPE) for sensing hydrogen peroxide (H₂O₂). The bare and PdNP-modified GPEs were characterized by cyclic voltammetry and SEM. The two electrodes displayed distinct electrocatalytic activities in response to the electrochemical reduction of H₂O₂. The amperometric detection limits were 45 nM and 0.58 mM, respectively, for the PdNP-GPE and bare-GPE, at an S/N of 3. The electrodes can be prepared simply and at low cost, and represent a promising tool for sensing H₂O₂.

Non-enzymatic hydrogen peroxide sensor using an electrode modified with iron pentacyanonitrosylferrate nanoparticles

An electrochemical sensor was developed for determination of hydrogen peroxide (HP) based on a carbon ceramic electrode modified with iron pentacyanonitrosylferrate (FePCNF). The surface of an iron-doped CCE was derivatized in a solution of PCNF by cycling the electrode potential between ?0.2 and +1.3 V for about 60 times. The morphology and the composition of the resulting electrode were characterized by scanning electron microscopy and Fourier transform infrared techniques. The electrode displayed excellent response to the electro-oxidation of HP which is linearly related to its concentration in the range from 0.5 μM to 1300 μM. The detection limit is 0.4 μM, and the sensitivity is 849 A M ^?1?cm ^?2. The modified electrode was used to determination of HP in hair coloring creams as real samples.