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.     

Indirect electrosynthesis of peracetic acid using hydrogen peroxide generated in situ in a gas diffusion electrode

Indirect electrochemical oxidation of acetic to peracetic acid in aqueous solutions using hydrogen peroxide generated in situ from O₂ in a gas diffusion electrode was studied. The use of sulfuric acid and ammonium molybdate as catalysts accelerated the formation of peracetic acid during the electrolysis, and the use of both catalysts allowed us to prepare 0.02 M solutions. The limiting stage of the electrosynthesis of peracetic acid was the chemical interaction of the substrate with the generated H₂O₂. The desired product mainly formed during the storage of the reaction mixture after the electrosynthesis. In electrolytes with more than 3.5 M acetic acid, the electrochemical activity of the gas-diffusion cathode decreased.     

Biosensor for determination of hydrogen peroxide based on catalase activity of human erythrocytes

A hydrogen peroxide biosensor based on human erythrocytes is described. Erythrocytes are retained on the surface of an oxygen electrode by a semipermeable membrane. The response is based on the catalase activity of the erythrocytes. The sensitivity of 10^?4 mol 1^?1 and linearity from 1.5×10^?4 to 5×10^?3 mol^?1 are comparable to those of analogous enzyme biosensors for hydrogen peroxide determination. The greatest advantages of this biosensor are its easy preparation and a lifetime of 2 months together with good reproducibility (relative standard deviation <5%) and selectivity; only ascorbic acid appeared to interfere with the measurements.     

Selective spectrophotometric determination of vanadium in silicates with a new pyridylazophenol in the presence of hydrogen peroxide

The synthesis of a new heterocyclic azo compound, 2-(3,5-dibromo-4-methyl-2-pyridylazo)-5-diethylaminophcnol (3,5-Br-MEPADAP is described. The dye forms an intensely coloured (ε=4.11·10⁴ 1 mole^-1 cm^-1 at 615 nm) unstable chelate with vanadium(V) in weakly acidic medium. However, vanadium(V) reacts with 3,5-Br-MEPADAP and hydrogen peroxide in 0.5 M sulphuric acid to form a stable 1:1:1 ternary complex which is extractable in several solvents. In the presence of fluoride, the reaction is highly selective for vanadium(V); only large amounts of halides, oxidizing and reducing agents interfere. The effective molar absorptivity is 5.43 ·10⁴ 1 mole^-1 cm^-1 at 615 nm in chloroform. The reagent system was applied for the direct spectrophotometric determination of vanadium in a wide range of silicates; the average relative standard deviation was 0.45 %. The accuracy of the vanadium values obtained for ten international standard rocks compares well with the currently accepted most probable values.     

Time-resolved enzymatic determination of glucose using a fluorescent europium probe for hydrogen peroxide

An enzymatic assay for glucose based on the use of the fluorescent probe for hydrogen peroxide, europium(III) tetracycline (EuTc), is described. The weakly fluorescent EuTc and enzymatically generated H₂O₂ form a strongly fluorescent complex (EuTc–H₂O₂) whose fluorescence decay profile is significantly different. Since the decay time of EuTc–H₂O₂ is in the microseconds time domain, fluorescence can be detected in the time-resolved mode, thus enabling substantial reduction of background fluorescence. The scheme represents the first H₂O₂-based time-resolved fluorescence assay for glucose not requiring the presence of a peroxidase. The time-resolved assay (with a delay time of 60 s and using endpoint detection) enables glucose to be determined at levels as low as 2.2 mol L^–1, with a dynamic range of 2.2–100 mol L^–1. The method also was adapted to a kinetic assay in order to cover higher glucose levels (mmol L^–1 range). The latter was validated by analyzing spiked serum samples and gave a good linear relationship for glucose levels from 2.5 to 55.5 mmol L^–1. Noteworthy features of the assay include easy accessibility of the probe, large Stokes shift, a line-like fluorescence peaking at 616 nm, stability towards oxygen, a working pH of approximately 7, and its suitability for both kinetic and endpoint determination.     

过氧化氢存在下平行催化氢波法测定奥沙普秦

在0.2mol/LKH2PO4-Na2HPO4(pH5.5±0.1)支持电解质中,奥沙普秦产生一催化氢波,峰电位Ep=-1.25V(vs.SCE)。当1×10-2mol/LH2O2存在时,该催化氢波的峰电流增加12倍,峰电位基本不变,产生一较灵敏的平行催化氢波。其二阶导数峰峰电流ip″与奥沙普秦浓度在1.0×10-7~2.6×10-5mol/L范围内呈线性关系(r=0.9995,n=10),检出限为5.0×10-8mol/L。该方法可用于药物制剂中奥沙普秦含量的测定。     

New water-soluble hydrogen donors for the enzymatic spectrophotometric determination of hydrogen peroxide

Eight N -alkyl-N-V-sulphopropylaniline derivatives have been synthesized and assessed as water-soluble hydrogen donors for the spectrophotometric determination of hydrogen peroxide in the presence of peroxidase. The sodium salts of N-ethyl-N-sulphopropylaniline (ALPS), N-ethyl-N-sulphopropyl-m-toluidine (TOPS) and N -ethyl-N-sulphopropyl-m-anisidine (ADPS) are recommended. They have excellent water solubilities, and the optimum pH range for oxidative condensation with 4-aminoantipyrine in the presence of hydrogen peroxide and peroxidase is 5.5–9.5. The absorbances of the resulting chromogens are 2–3 times higher than that achieved with phenol. The molar absorptivities of the chromogens with 4-aminoantipyrine are 41300 (ALPS, λ_max 561 nm), 37400 (TOPS, λ_max 550 nm) and 27900 (ADPS, λ_max 540 nm). Calibration graphs for the determination of hydrogen peroxide in the presence of a control serum are linear for 7–40 × 10^-6 mol H₂O₂ l^-1.     

Spectrofluorometric determination of kynurenic acid with horseradish peroxidase in the presence of hydrogen peroxide.

The catalytic activity of horseradish peroxidase (HRP) in the presence of hydrogen peroxide has been investigated for the fluorescent derivatization of kynurenic acid under conditions with no exposure to light. Non-fluorescent kynurenic acid was converted into a fluorescent compound (Ex: 367 nm, Em: 470 nm) with HRP in the presence of hydrogen peroxide, and the optimum conditions of this fluorescent derivatization were investigated. Moreover, this fluorescent derivatization was developed for a spectrofluorometric determination of trace amounts of kynurenic acid by measuring the fluorescence intensity of the fluorescent compound. The calibration curve obtained was linear from 1.0 to 10.0 nmol of kynurenic acid in a 1.0 mL sample solution. The relative standard deviation at 5.0 nmol of kynurenic acid was 5.71% (n=5). By adjusting the bandwidths for both the excitation and emission to 15 nm, the calibration curve was also linear in the range between 0.1 to 1.0 nmol of kynurenic acid in a 1.0 mL sample solution. This method was applied to the fluorometric determination of trace amounts of kynurenic acid in the control sera.     

Differential amperometric determination of hydrogen peroxide in honeys using flow-injection analysis with enzymatic reactor

Hydrogen peroxide (H2O2) present in honey was rapidly determined by the differential amperometric method in association with flow-injection analysis (FIA) and a tubular reactor containing immobilized enzymes. A gold electrode modified by electrochemical deposition of platinum was employed as working electrode. Hydrogen peroxide was quantified in 14 samples of Brazilian commercial honeys using amperometric differential measurements at +0.60V vs. Ag/AgCl((sat)). For the enzymatic consumption of H2O2, a tubular reactor containing immobilized peroxidase was constructed using an immobilization of enzymes on Amberlite IRA-743 resin. The linear dynamic range in H2O2 extends from 1 to 100 x 10(-6) mol L(-1), at pH 7.0. At flow rate of 2.0 mL min(-1) and injecting 150 microL sample volumes, the sampling frequency of the 90 determinations per hour is afforded. This method is based on three steps involving the flow-injection of: (1) the sample spiked with a standard solution, (2) the pure sample and (3) the enzymatically treated sample with peroxidase immobilized. The reproducibility of the current peaks for hydrogen peroxide in 10(-5) mol L(-1) range concentration showed a relative standard deviation (R.S.D.) better than 1%. The detection limit of this method is 2.9 x 10(-7) mol L(-1). The honey samples analyses were compared with the parallel spectrophotometric determination, and showed an excellent correlation between the methods.     

Selective determination of uric acid in the presence of ascorbic acid using a penicillamine self-assembled gold electrode

The electrochemical behaviors of uric acid (UA) at the penicillamine (Pen) self-assembled monolayers modified gold electrode (Pen/Au) have been studied. The Pen/Au electrode is demonstrated to promote the electrochemical response of UA by cyclic voltammetry (CV). The diffusion coefficient D of UA is 6.97 × 10⁻⁶ cm² s⁻¹. In differential pulse voltammetric (DPV) measurements, the Pen/Au electrode can separate the UA and ascorbic acid (AA) oxidation potentials by about 120 mV and can be used for the selective determination of UA in the presence of AA. The detection limit was 1 × 10⁻⁶ mol L⁻¹. The modified electrode shows excellent sensitivity, good selectivity and antifouling properties.     

Thermal decomposition of hydrogen peroxide in the presence of sulfuric acid

Hydrogen peroxide (H₂O₂) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition reaction of H₂O₂ mixed with sulfuric acid (H₂SO₄) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic onset temperature (T ₀), heat of decomposition (ΔH _d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations of H₂SO₄, the experimental data of T ₀, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H₂O₂ and H₂O₂ mixed with H₂SO₄ (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems.     

A novel biosensor for specific determination of hydrogen peroxide: catalase enzyme electrode based on dissolved oxygen probe

A biosensor for the specific determination of hydrogen peroxide was developed using catalase (EC 1.11.1.6) in combination with a dissolved oxygen probe. Catalase was immobilized with gelatin by means of glutaraldehyde and fixed on a pretreated teflon membrane served as enzyme electrode. The electrode response was maximum when 50 mM phosphate buffer was used at pH 7.0 and at 35 degrees C. The biosensor response depends linearly on hydrogen peroxide concentration between 1.0x10(-5) and 3.0x10(-3) M with a response time of 30 s. The sensor is stable for >3 months so in this period >400 assays can be performed.     

Flow-injection spectrophotometric determination of azithromycin in pharmaceutical formulations using p-chloranil in the presence of hydrogen peroxide.

A flow-injection (FI) spectrophotometric procedure exploiting merging zones is proposed for the determination of azithromycin in pharmaceutical formulations. The method is based on the reaction of azithromycin with tetrachloro-p-benzoquinone (p-chloranil) accelerated by hydrogen peroxide and conducted in a methanol medium, producing a purple-red color compound (lambda(max) = 540 nm). The FI system and the experimental conditions were optimized using a multivariate method. Beer's law is obeyed in a concentration range of 50 - 1600 microg mL(-1) with an excellent correlation coefficient (r = 0.9998). The detection limit and the quantification limit were 6.6 and 22.1 microg mL(-1), respectively. No interference was observed from the common excipients, and the recoveries were within 98.6 to 100.4%. The procedure was applied to the determination of azithromycin in pharmaceuticals with a high sampling rate (65 samples h(-1)). The results obtained by the proposed method were in good agreement with those obtained by the comparative method at 95% confidence level.     

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.     

对甲苯磺酸/活性炭/双氧水体系选择氧化苯乙烯生成苯甲醛(英文)

以双氧水为氧化剂,研究了对甲苯磺酸和活性炭体系选择氧化苯乙烯生成苯甲醛反应性能。考察了反应时间、温度、催化剂用量、苯乙烯和双氧水摩尔比等对苯乙烯选择氧化性能的影响.结果表明,对甲苯磺酸和活性炭的用量和用量比是一个重要因素,但对甲苯磺酸的酸性对氧化反应活性影响不大.对甲苯磺酸和双氧水相互作用,经非自由基过程氧化苯乙烯.通过分解双氧水产生氢氧自由基,活性炭显著提高对甲苯磺酸和双氧水体系氧化苯乙烯活性.在惰性或还原气氛中高温处理活性炭能降低其表面含氧基团数量,增加碱性,有效分解双氧水,产生相对较多的OH自由基.与未处理的活性炭相比,高温处理的活性炭进一步提高了对甲苯磺酸和双氧水体系氧化苯乙烯活性,但降低了苯甲醛选择性.经磺化,在活性炭表面引入的–SO_3H基团比含氧基团(–OH,–COOH)更有效与双氧水作用氧化苯乙烯.     

Highly sensitive spectrophotometric determination of cobalt using o-hydroxyhydroquinonephthalein and hydrogen peroxide in the presence of mixed surfactants

Summary The effects of cobalt(II) and surfactants on the decomposition of various xanthene dyes by hydrogen peroxide have been systematically investigated. A simple and highly sensitive spectrophotometric determination of cobalt(II) (0.05 1.2 g/10 ml) is proposed. The method is based on the catalytic effect of cobalt(II) on the oxidation of o-hydroxyhydroquinonephthalein (Qnph) by hydrogen peroxide. The proposed catalytic spectrophotometric determination was sensitive, selective, reproducible and virtually unaffected by the presence of other ions; the effective molar desorptivity was 4.2×10⁸ l/mol per cm, Sandell sensitivity was 0.15 pg/cm², and the relative standard deviation was 3.2% at 0.6 ng/10 ml (n=5). The selective assays of cobalt(II) in water samples were also investigated with satisfactory results (95% 101%).

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Hochempfindliche Spektralphotometrische Kobaltbestimmung mit Hilfe von o-Hydroxyhydrochinonphthalein und Wasserstoffperoxid in Gegenwart von oberflÄchenaktiven Substanzen

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Application of xanthene derivatives in analytical chemistry. Part LXIX. Part LXVIII see ref. [1]     

Selective determination of L-dopa in the presence of ascorbic acid and uric acid using a 3D graphene foam

Three-dimensional interconnected network graphene foam (GF) was synthesized by chemical vapor deposition. The GF was transferred onto indium tin oxide glass, acting as an electrode for the selective determination of L-dopa in the presence of ascorbic and uric acid. Using differential pulse voltammetry (DPV) method, the oxidation peak current is well linear with L-dopa concentration in the range of 0.05–1 μM with a sensitivity of 2.64 μA μM^?1 and in the range of 1–40 μM with a sensitivity of 1.82 μA μM^?1. The detection limit of this electrode for L-dopa is about 20 nM. The proposed electrode can also effectively avoid the interference of ascorbic acid and uric acid, making the proposed sensor suitable for the accurate determination of L-dopa in human urine fluids. This electrode will have a wide range of potential application prospect in electrochemical detection.     

Spectrophotometric determination of hydrogen peroxide by using the cleavage of Eriochrome black T in the presence of peroxidase

A new hydrogen donor for peroxidase, Eriochrome black T, was reported for the first time. Steady-state catalytic velocity depends upon enzyme and substrate concentrations, and a Michaelis-Menten K(m) value of 1.72x10(-5) mol l(-1) and a V(max) value of 4.43x10(-3) s(-1) were measured at pH 8.6. Trace amount of hydrogen peroxide (2x10(-7)-1.0x10(-5) mol l(-1)) was determined in aqueous solution by using the cleavage of Eriochrome black T catalyzed by peroxidase. The method is simple and practical, with high sensitivity and enzymatic activity.