Nickel hexacyanoferrate nanoparticles/nano silver coated multiwalled carbon nanotubes nanocomposite for the detection of hydrogen peroxide

A new nanocomposite was developed by combination of nickel hexacyanoferrate nanoparticles (NiNP) and nano silver coated multiwalled carbon nanotubes (nano Ag-MWNTs). The NiNP/nano Ag-MWNTs nanocomposite was charactered by scanning electron microscopy (SEM). The NiNP/nano Ag-MWNTs nanocomposite modified glassy carbon (GC) electrode was used to investigate the electrochemical reduction of hydrogen peroxide. The results showed that NiNP and nano Ag-MWNTs provided the synergistic effect toward this process. The obtained NiNP/nano Ag-MWNTs/GC electrode showed a wide linear response range of 1 × 10^?6 to 1 × 10^?4 and 5 × 10^?4 to 0.01 M hydrogen peroxide with correlation coefficients of 0.998 and 0.997, fast response time (2 s), and good selectivity toward the electrocatalytic reduction of hydrogen peroxide. The detection limit (S/N = 3) of hydrogen peroxide was 5 × 10^?7 M.     

A Multicommuted Flow‐based System for Hydrogen Peroxide Determination by Chemiluminescence Detection Using a Photodiode

Abstract

A simple, rapid, and automated assay for hydrogen peroxide in pharmaceutical samples was developed by combining the multicommutation system with a chemiluminescence (CL) detector. The detection was performed using a spiral flow‐cell reactor made from polyethylene tubing that was positioned in front of a photodiode. It allows the rapid mixing of CL reagent and analyte and simultaneous detection of the emitted light. The chemiluminescence was based on the reaction of luminol with hydrogen peroxide catalyzed by hexacyanoferrate(III).

The feasibility of the flow system was ascertained by analyzing a set of pharmaceutical samples. A linear response within the range of 2.2–210 µmol l^?1 H₂O₂ with a LD of 1.8 µmol l^?1 H₂O₂ and coefficient of variations smaller than 0.8% for 1.0×10^?5 mol l^?1 and 6.8×10^?5 mol l^?1 hydrogen peroxide solutions (n=10) were obtained. Reagents consumption of 90 µg of luminol and 0.7 mg of hexacyanoferrate(III) per determination and sampling rate of 200 samples per hour were also achieved.     

Peroxyoxalate chemiluminescence of 1,4-dihydroxy-3-methyl-thioxanthone and quenching effect of β-cyclodextrin

The chemiluminescence generated from the reaction of bis(2,4,6-trichlorophenyl) oxalate (TCPO), hydrogen peroxide and 1,4-dihydroxy-3-methyl-thioxanthone (DMT) was investigated. Effects of reacting components, solvent and concentrations of TCPO, sodium salicylate, hydrogen peroxide and DMT were studied and their optimal values were determined. In addition, the influences of β-Cyclodextrin (β-CD) on the peroxyoxalate chemiluminescence (PO-CL) system of DMT were examined at optimized condition. The results showed that the presence of β-CD causes both enhancing and quenching effects on PO-CL system of DMT based upon its concentration. The Stern–Volmer quenching constant (K _q) was evaluated as 2.32?×?10⁴?M^?1 (R ^2?= 0.991) by creating a linear regression plot on experimentally obtained data. This study resulted in satisfactorily determination of β-CD in the range 5.0?×?10^?6 to 1.0?×?10^?4?M.     

A solid-state chemiluminescence detector for hydrogen peroxide based on an immobilized luminophore : Application to Rain Water

The construction and functioning of a chemiluminescence detector for hydrogen peroxide is described. It is based on peroxyoxalate chemiluminescence and consists of a two-bed reactor packed with solid trichlorophenyloxalate (TCPO) and 3-aminofluoranthene immobilized on controlled pore glass beads. Optimal conditions (pH, solvent, TCPO purity) for flow-independent operation are discussed. Samples can be injected into a moving stream or directly into the monitor with a syringe so as to provide a manually operated field monitor. The detection limit is 1.5 × 10^?8 M, and calibration graphs are linear over six orders of magnitude. The r.s.d. for the manual monitoring mode is ±3% for 17 μg l^?1 hydrogen peroxide. A sample throughput of 100 h^?1 is possible in the flow injection mode, and 40 samples h^?1 for manual injection.     

Non-enzymatic hydrogen peroxide sensor based on a nanoporous gold electrode modified with platinum nanoparticles

A novel non-enzymatic electrochemical sensor based on a nanoporous gold electrode modified with platinum nanoparticles was constructed for the determination of hydrogen peroxide (H₂O₂). Platinum nanoparticles exhibit good electrocatalytic activity towards hydrogen peroxide. The nanoporous gold (NPG) increases the effective surface area and has the capacity to promote electron-transfer reactions. With electrodeposition of Pt nanoparticles (NPs) on the surface of the nanoporous gold, the modified Au electrode afforded a fast, sensitive and selective electrochemical method for the determination of H₂O₂. The linear range for the detection of H₂O₂ was from 1.0 × 10^?7 M to 2.0 × 10^?5 M while the calculated limit of detection was 7.2 × 10^?8 M on the basis of the 3σ/slope (σ represents the standard deviation of the blank samples). These findings could lead to the widespread use of electrochemical sensors to detect H₂O₂.     

Flow injection analysis for glucose and urea with enzyme reactors and on-line dialysis

A flow injection system for glucose and urea determination is described. The glucose determination uses immobilized glucose oxidase in a reactor designed to give 100% substrate conversion. The hydrogen peroxide formed is converted to a coloured complex with 4-aminophenazone and N,N-dimethylaniline. The coupling is catalysed by a reactor containing immobilized peroxidase. The coloured complex is measured in a flow-through spectrophotometric cell. Urea is converted to ammonia in a reactor with immobilized urease and detected with an ammonia gas membrane electrode. Proteins and other interfering species from serum samples are removed in an on-line dialyzer. Calibration curves are linear for glucose in the range 1.6 × 10^-4–1.6 × 10^-2 M and for urea in the range 10^-4–10^-1 M. The samples are 25 μl for glucose determination and 100 μl for urea determination. Linear ranges can be changed by varying the sample sizes. The effects of the dialyser, enzyme reactors and detectors on dispersion are evaluated.     

Flow-injection determination of sulphite and assay of sulphite oxidase

Sulphite (1–80 × 10^?5 M) in formaldehyde-stabilized solutions is determined by injection into a flowing stream of pH 8.5 phosphate buffer, passing through a mini-column of sulphite oxidase immobilized on controlled-pore glass, with amperometric detection of the hydrogen peroxide produced. Sulphite oxidase (5–100 U l^?) is determined by injection into a flowing stream of formaldehyde-stabilized 2 × 10^?3 M sodium sulphite in pH 8.0 phosphate buffer; hydrogen peroxide is again monitored.     

Grape tissue-based electrochemical sensor for the determination of hydrogen peroxide

The use of grape tissue as a source of catalase for the determination of hydrogen peroxide is reported. A slice of grape tissue attached to the membrane of a Clark-type oxgen sensor was used to monitor the oxidation of hydrogen peroxide by catalase. At the steady state, the sensor responds linearly to hydrogen peroxide in the concentration range 1 × 10^?5–5 × 10^?4 M. The response time (T₉₀) was of the order of 1 min for this sensor. No interference was observed from ethanol, amino acids, glucose and lactic acid. The long-term stability of the grape tissue sensor was much better than previously reported immobilized enzyme and liver tissue-based hydrogen peroxide sensors.     

Delignification of deciduous wood under the action of hydrogen peroxide and ozone

Kinetic curves of the dependence of ozone specific absorption (Q _{r, sp} ) upon the ozonation of aspen wood pretreated with solutions of hydrogen peroxide of various concentrations (from 5 × 10^?4 to 2 × 10^?1 mol/L) are obtained. The water content in the samples being 56 ± 3%. The initial rate of ozone absorption and total ozone consumption (Q _inlet) are determined. Wood samples are investigated by IR and UV diffuse reflection spectroscopy. Based on the kinetics and spectral data, it is concluded that pretreating wood with a H₂O₂ solution allows the degree of delignification (DD) to be increased at a constant Q _inlet value. The DD is maximal at $ C_{H_2 O_2 } = 5 \times 10^{ - 3} $ mol/L and is 88% in contrast to a sample ozonated without H₂O₂ (DD = 85%). The role of pretreatment with hydrogen peroxide and the subsequent action of the O₃/H₂O₂ system in the process of delignification of wood is analyzed.     

Self-assembling of Prussian blue nanocubic particles on nanoporous glassy carbon and its use in the electrocatalytic reduction of hydrogen peroxide

In this paper, self-assembled Prussian blue nanocubic particles on nanoporous glassy carbon was developed. The morphology of the PBNP-modified porous glassy carbon was characterized by scanning electron microscopy. The PBNP-GCE-red film-modified electrode was used for the sensitive detection of hydrogen peroxide. The electrochemical behavior of the resulting sensor was investigated using cyclic voltammetry and chronoamperometry. The value of α, k _cat, and D was calculated as 0.35, 1.7 × 10⁵ cm³ mol^?1 s^?1, and 2.6 × 10^?5 cm² s^?1, respectively. The calibration curve for hydrogen peroxide determination was linear over 0–600 μM with a detection limit (S/N = 3) of 0.51 μM.     

Dipole moment and conformational properties of poly(methacrylic acid) in solvents with hydrogen bonding

Dielectric polarization of solutions of un-ionized linear poly(methacrylic acid) in polar associated liquids is studied in the temperature range 20–50°C. The solutions are in methanol, with the molar fraction of polymer units x ₂ = (3 × 10^?3)?(1.5 × 10^?2), and in water, with x ₂ = (4 × 10^?5)?(4 × 10^?3). The permittivity ε₁₂ of the polyacid solutions in methanol is shown to be lower than the permittivity of the pure solvent ε₁; the permittivity of the polyacid solutions in water exceeds ε₁ of water in the concentration range x ₂ = (4 × 10^?5)?(2.13 × 10^?4) and becomes lower than ε₁ as the polymer concentration in the solution increases further. A procedure for estimating the dipole moment μ₂ per monomer unit of the polymer macromolecule in solution is proposed. The estimation is based on Buckingham’s statistical polarization theory for a two-component mixture of polar molecules under the conditions of infinite dilution. The μ₂ values amount to 2.76–2.14 D (x ₂ < 1.5 × 10^?2) in methanol at 20–50°C and to 11.4?3.8 D (x ₂ < 2.13 × 10^?4) in water at 20–40°C. The difference in the dipole moments of the polyacid and in the patterns of their temperature dependences in methanol and in water is due to the effects of the polyacid-solvent hydrogen bonding, to intramacromolecular hydrogen bonds, and to specificity of the local structure of the solvent. It is shown that the μ₂ value corresponds to the dipole moment of the solvates and decreases with temperature owing to changes in the stoichiometry of the solvates, to the formation of cyclic associates in the macromolecule, and to conformational changes in the chain.     

Nanostructured Alpha‐Nickel Hydroxide Electrodes for High Performance Hydrogen Peroxide Sensing

Nanostructured alpha‐nickel hydroxide (α‐Ni(OH)₂) immobilized on a Fluorine‐doped Tin Oxide (FTO) surface was explored for the construction of hydrogen peroxide amperometric Flow Injection Analysis (FIA) sensors. Their notable electrocatalytic activity and heterogeneous electron‐transfer rate were confirmed by the appearance of a broad and intense peak associated with the oxidation of hydrogen peroxide and the enhancement of sensibility in hydrodynamic conditions. The α‐Ni(OH)₂ electrodes exhibited a broad dynamic range (5×10^?6 to 1×10^?3 mol L^?1), low detection limit (2×10^?7 mol L^?1), good repeatability (RSD=1.29 % for 20 successive analyses), and a sensitivity greater than 500 µA mmol^?1 L^?1 cm^?2.     

Electrochemical and kinetic study of oxygen in a perfluorotributylamine emulsion

Oxygen can be determined in a perfluorotributylamine emulsion used as a blood substitute by coulometry and polarography. The oxygen uptake of the emulsion (4.3 × 10^?3 mol l^?1 or 11 ml-% at 25°C and P_O2 = 760 mm Hg) is about three times greater than that of water. The adsorption of surfactant on a dropping mercury electrode changes the electrochemical parameters E_{$\text{1}\text{2}$}, α and k₃. The marked difference between the diffusion coefficients of oxygen and hydrogen peroxide (ratio 2.6) seems to be proceed from the ejection of oxygen molecules from the perfluorotributylamine droplets and from the insolubility of hydrogen peroxide molecules in the droplets. The constant rate of oxygen release by these droplets was estimated to be 10⁴ s^?1 by a stopped-flow spectrophotometric method. This constant rate seems to be linked with the particle diameter (0.2 μm) and the diffusion coefficient in the perfluorotributylamine droplets (1.6 × 10^?6 cm² s^?1).     

Study On The Catalytic Reaction Of β-Cd-Hemin Using 2, 3, 4-Trichlorophenol As Substrate And Analytic Application

ABSTRACT|The catalytic activity of various mimetic enzymes instead of the peroxidase have been investigated by 4-aminoantipyrine (4-AAP) and 2, 3, 4-trichlorophenol (TCP) to form a dye utilizing hydrogen peroxide as hydrogen acceptor. The different Chlorophenolic derivatives, which act as a substrate in β-CD-hemin-H₂O₂-4-AAP catalytic reaction, have been systematically studied.|Meanwhile, the relationship of structure-effect for the β-CD-hemin as catalyst, and chlorphenols as substrate has been respectively discussed. The mechanism of catalytic reaction has been investigated. The results showed that β-CD-hemin was the best mimetic enzyme for peroxidase among those tested and TCP was a good substrate for the determination of hydrogen peroxide with β-CD-hemin. The method for the determination of hydrogen peroxide was proposed using 4-AAP-TCP system with β-CD-hemin as catalyst. A linear calibration graph was obtained over the H₂O₂ concentration of 4.8×10-^?8-7.7×10-^?5M, and the relative standard deviation at a H₂O₂ concentration of 2.8×10-^?5M was 2.5%. The apparent molar absorptivity of the chromogenic reaction for H₂O₂ was 1.54× 10⁴ L.mol-^?1.cm^?1. Satisfactory results were obtained in the determination of H₂O₂ in synthetic samples by this method.

Also, the method was coupled with the glucose oxidation reaction to determination glucose in human serum.     

Synergetic effect of Prussian blue film with gold nanoparticle graphite–wax composite electrode for the enzyme-free ultrasensitive hydrogen peroxide sensor

Enzyme-free amperometric ultrasensitive determination of hydrogen peroxide (H₂O₂) was investigated using a Prussian blue (PB) film-modified gold nanoparticles (AuNPs) graphite–wax composite electrode. A stable PB film was obtained on graphite surface through 2-aminoethanethiol (AET)-capped AuNPs by a simple approach. Field emission scanning electron microscope studies results in formation of PB nanoparticle in the size range of 60–80 nm. Surface modification of PB film on AET–AuNPs–GW composite electrode was confirmed by Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy studies. Highly sensitive determination of H₂O₂ at a peak potential of ?0.10 V (vs. SCE) in 0.1 M KCl PBS, pH?=?7.0) at a scan rate of 20 mVs^?1 with a sensitivity of 23.58 μA/mM was observed with the modified electrode using cyclic voltammetry. The synergetic effect of PB film with AuNPs has resulted in a linear range of 0.05 to 7,800 μM with a detection limit of 0.015 μM for H₂O₂ detection with the present electrode. Chronoamperometric studies recorded for the successive additions of H₂O₂ with the modified electrode showed an excellent linearity (R ²?=?0.9932) in the range of 4.8?×?10^?8 to 7.4?×?10^?8 M with a limit of detection of 1.4?×?10^?8 M. Selective determination of H₂O₂ in presence of various interferents was successfully demonstrated. Human urine samples and stain remover solutions were also investigated for H₂O₂ content.     

Self-assembly of ultra-small gold nanoparticles on an indium tin oxide electrode for the enzyme-free detection of hydrogen peroxide

A novel enzyme-free electrochemical sensor for H₂O₂ was fabricated by modifying an indium tin oxide (ITO) support with (3-aminopropyl) trimethoxysilane to yield an interface for the assembly of colloidal gold. Gold nanoparticles (AuNPs) were then immobilized on the substrate via self-assembly. Atomic force microscopy showed the presence of a monolayer of well-dispersed AuNPs with an average size of ~4 nm. The electrochemical behavior of the resultant AuNP/ITO-modified electrode and its response to hydrogen peroxide were studied by cyclic voltammetry. This non-enzymatic and mediator-free electrode exhibits a linear response in the range from 3.0?×?10^?5 M to 1.0?×?10^?3 M (M?=?mol?·?L^?1) with a correlation coefficient of 0.999. The limit of detection is as low as 10 nM (for S/N?=?3). The sensor is stable, gives well reproducible results, and is deemed to represent a promising tool for electrochemical sensing.

Direct electrochemistry and bioelectrocatalysis of a class II non-symbiotic plant haemoglobin immobilised on screen-printed carbon electrodes

In this study, direct electron transfer (ET) has been achieved between an immobilised non-symbiotic plant haemoglobin class II from Beta vulgaris (nsBvHb2) and three different screen-printed carbon electrodes based on graphite (SPCE), multi-walled carbon nanotubes (MWCNT-SPCE), and single-walled carbon nanotubes (SWCNT-SPCE) without the aid of any electron mediator. The nsBvHb2 modified electrodes were studied with cyclic voltammetry (CV) and also when placed in a wall-jet flow through cell for their electrocatalytic properties for reduction of H₂O₂. The immobilised nsBvHb2 displayed a couple of stable and well-defined redox peaks with a formal potential (E°′) of ?33.5 mV (vs. Ag|AgCl|3 M KCl) at pH 7.4. The ET rate constant of nsBvHb2, k _s, was also determined at the surface of the three types of electrodes in phosphate buffer solution pH 7.4, and was found to be 0.50 s^?1 on SPCE, 2.78 s^?1 on MWCNT-SPCE and 4.06 s^?1 on SWCNT-SPCE, respectively. The average surface coverage of electrochemically active nsBvHb2 immobilised on the SPCEs, MWCNT-SPCEs and SWCNT-SPCEs obtained was 2.85?×?10^?10 mol cm^?2, 4.13?×?10^?10 mol cm^?2 and 5.20?×?10^?10 mol cm^?2. During the experiments the immobilised nsBvHb2 was stable and kept its electrochemical and catalytic activities. The nsBvHb2 modified electrodes also displayed an excellent response to the reduction of hydrogen peroxide (H₂O₂) with a linear detection range from 1 μM to 1000 μM on the surface of SPCEs, from 0.5 μM to 1000 μM on MWCNT-SPCEs, and from 0.1 μM to 1000 μM on SWCNT-SPCEs. The lower limit of detection was 0.8 μM, 0.4 μM and 0.1 μM at 3σ at the SPCEs, the MWCNT-SPCEs, and the SWCNT-SPCEs, respectively, and the apparent Michaelis–Menten constant, $ {\hbox{K}}_{\rm{M}}^{\rm{app}} $ , for the H₂O₂ sensors was estimated to be 0.32 mM , 0.29 mM and 0.27 mM, respectively.     

Flow-injection amperometric determination of oxalate with immobilized oxalate oxidase

Oxalate is immobilized on controlled-pore glass and is used on-line in a glass minicolumn (2.5×25 mm). The hydrogen peroxide formed is detected amperometrically. Oxalate (6×10^?6?9×10^?4 M) is determined in a flowing stream of pH 3.5 citrate (or succinate) buffer. As little as 20 ng (in 40 μl; 5.7×10^?6 M) of oxalate can be detected. Copper inhibition can be removed either by adding EDTA to the carrier stream or incorporating a chelating-resin minicolumn into the flow system prior to the enzyme column.     

An Organic Sol‐Gel Film as Modifier to Construct Biosensor

A new amperometric biosensor for hydrogen peroxide (H₂O₂) was developed by adsorbing hemoglobin (Hb) on an organic sol‐gel film. The organic sol‐gel was prepared using resorcinol and formaldehyde as monomers. This sol‐gel film shows a biocompatible microenvironment for retaining the native activity of the adsorbed Hb. The direct electron transfer between Hb and electrode is achieved. Hb adsorbed on the film shows an enzyme‐like catalytic activity for the reduction of H₂O₂. The reduction peak currents are proportional linearly to the concentration of hydrogen peroxide in the range of 6×10^?8 to 3.6×10^?6 M, with a detection limit of 2.4×10^?8 M (S/N=3). This research enlarges the applications of organic sol‐gel materials in biosensor field.     

The effect of thallium ions on the gold dissolution rate in thiosulfate electrolytes

The effect of TlNO₃ additions in the concentration (c ₁) range from 5 × 10^?6 to 1 × 10^?4 M on the anodic dissolution of gold in sodium thiosulfate solutions with the concentration (c ₂) from 0.005 to 0.2 M is studied by voltammetry on the electrode surface renewed by cutting off a thin metal layer immediately in solution and also by the quartz-crystal microbalance method. For c ₂ = 0.2 M, as c ₁ increases from 5 × 10^?6 to 1 × 10^?4 M, the gold anodic dissolution rate is observed to increase from 0.02 (in the absence of TlNO₃) to 0.75 mA/cm² for c ₁ = 7.5 × 10^?5 M according to a nearly linear law. The dissolution accelerates because the effective values of the transfer coefficient and the exchange current density increase from 0.2 and 4 ??A/cm² (in the absence of TlNO₃ admixtures) to 0.47 and 35 ??A/cm² (for c ₁ = 1 × 10^?4), respectively. Experiments with the renewal of the electrode surface in the course of electrolysis suggest that the gold dissolution is catalyzed in the presence of thallium ions by the adsorption mechanism and also as the result of the mixed kinetics of their adsorption on the electrode surface.