Ferrocyanide Ions Research Articles

基于与铁氰化钾和Zn<sup>2+</sup>作用共振光散射法测定异烟肼

In acidic medium, a novel resonance light scattering (RLS) analytical method of isoniazid is developed based on RLS signal enhancement due to the interaction of Zn²⁺ and ferrocyanide ion derived from ferricyanide ion by isoniazid. The enhanced RLS intensity at 345nm is proportional to the content of isoniazid in a range of 0.01~1.0 μg/mL. The linear regression equation is Δ<italic>I</italic>_RLS = 136.1 + 4239c (<italic>c</italic>, μg/mL). The correlation coefficient (<italic>r</italic>) is 0.9984. The limit of detection (3<italic>σ</italic>) is 3.8 ng/mL. This method has been successfully applied to the determination of isoniazid in pharmaceutical and serum samples. In this work, the reaction mechanism and the reasons of scattering enhanced have been also investigated by using absorption spectra, dynamic light scattering and SEM.

New approaches to reprocessing of oxide nuclear fuel

Dissolution of UO2, U3O8, and solid solutions of actinides in UO2, including those containing Cs, Sr, and Tc, in weakly acidic (pH 0.9–1.4) aqueous solutions of Fe(III) nitrate or chloride was studied. Complete dissolution of the oxides is attained at a molar ratio of Fe(III) nitrate or chloride to uranium of 1.6 or 2.0, respectively. In the process, actinides pass into the solution in the form of U(VI), Np(V), Pu(III), and Am(III). At 60°C, actinide oxides dissolve in these media faster than at room temperature. In the solutions obtained, U(VI) and Pu(III) are stable both at room temperature and at elevated temperatures (60°C), and also at high U concentrations (up to 300 mg ml−1) typical of process solutions (6–8 M HNO3, ∼60–80°C). After the oxide fuel dissolution, U and Pu are recovered from the solution by peroxide precipitation. In so doing, the content of Fe, Tc, Cs, and Sr in the precipitate does not exceed ∼0.05 wt %. From the solution after the U and Pu separation, the fission lanthanides, Tc, Cs, and Sr can be recovered by precipitation of Fe hydroxides in the presence of ferrocyanide ions and can be immobilized in appropriate matrices suitable for long-term and environmentally safe storage.

Insights on the Mechanism of Insoluble-to-Soluble Prussian Blue Transformation

The electrochemical transformation of the soluble form of Prussian blue (PB) material from the insoluble form was monitored using electrochemical, gravimetric, acoustic, and spectroscopic techniques simultaneously. The described combination of in situ techniques represents an innovative tool for measurement in electrochemistry, which provides complementary information on the electrochemical systems. The insoluble-to-soluble PB transformation process takes place during the successive voltammetric cycles between the mixed valence form (PB) and the fully reduced form [Everitt’s salt (ES)]. One of the processes that takes place is the exit of free ions occluded in the vacancies of the insoluble PB crystalline framework during the fresh PB electrodeposit process. In potassium salt solutions, the exit of each ferrocyanide ion is compensated by the entrance of two potassium ions and six hydroxyl anions. This species exchange increases the manifestation of viscoelastic phenomena of the rigid skeleton from the insoluble PB form to the soluble one, which could facilitate the appearance of an internal magnetic field at room temperature during the soluble voltammetric cycle.

Front propagation in the bromate–sulfite–ferrocyanide–aluminum (III) system: Autocatalytic front in a buffer system

We study the propagation of pH fronts in a narrow, pseudo-one-dimensional strip of gel containing bromate, sulfite, ferrocyanide and aluminum ions. The front propagation speed v decreases with [ Al 3+] as 1 / v = 1 / v 0 + c [ Al 3 + ] , where c is a constant. We determine the diffusion coefficients of protons and ferricyanide ions and find that Al(OH) 3 loaded in agarose or acrylamide gels binds protons reversibly, thereby slowing the propagating fronts without significantly affecting the diffusion of ferricyanide ions. We present a model that qualitatively reproduces the experimental behavior, and we suggest some general principles governing autocatalytic fronts in buffered systems.

&lt;b&gt;KINETICS AND MECHANISM OF PRUSSIAN BLUE FORMATION&lt;/b&gt;

The kinetics of reaction between ferrocyanide and ferric ions under acidic conditions was studied at fixed ionic strength (0.1 M) and (25 ± 0.1) o C by using the stopped flow technique, under limiting conditions of [ferrocyanide] and with other reactants in excess. The reaction had first-order dependence on ferrocyanide, Fe(III) and H + ion concentrations and had negative salt effect. On the basis of the experimental findings, a plausible mechanism for the formation of soluble form of Prussian blue (KFe{Fe(CN) 6 }x H 2 O) and rate law are proposed. The activation parameters for the title reaction are estimated. A relatively low energy of activation (23 kJ mol -1 ) and high negative entropy of activation (-231 J K -1 mol -1 ) agree well with the proposed mechanism and configuration of complex ion leading to the formation of insoluble Prussian blue, Fe 4 {Fe(CN) 6 } 3 y H 2 O. KEY WORDS : Prussian blue, Kinetics, Ferrocyanide, Salt effect, Ferricferrocyanide Bull. Chem. Soc. Ethiop. 2009 , 23(1), 47-54.

Carbon Electrodes Surface Modification in Hexane/CTAB-CTAmodified-butanol/Water System

The modification of graphite electrode surfaces with different hardness using hexane/CTAB-CTAmodified-butanol/water microemulsion forming system with inverse micelles (W/O) is presented. CTAB is modified by exchanging bromide ions of the surfactant with ferrocyanide ions in a salt solution. Carbon electrodes are modified by immersing them into a W/O microemulsion, followed by a rinsing step with pure water, and a potential cycling in a ferrocyanide solution. After this treatment, electrodes display two redox peaks, characteristic of strongly adsorbed species. The amount of adsorbed material at the electrode surface is greater for soft graphite electrodes than for hard ones. FTIR spectra of carbon electrodes before and after modification not show signal of C-C bonds and the increase of C-N signal from ferrocyanide ions attached to the surfactant. These results support the formation of a new bond between the surfactants tail and the carbon surface.

Diffusion Impedance in a Thin-Layer Cell: Experimental and Theoretical Study on a Large-Disk Electrode

Using an accurate thin-layer cell, the electrochemical impedance corresponding to the diffusion of ferro-cyanide ions was measured on a large-disk electrode covered by thin films of electrolyte. Experimental impedance diagrams obtained in a large frequency range (100 kHz−5 mHz) were in good agreement with those expected in the case of a spatially restricted linear diffusion impedance. For electrolyte film thicknesses lower than 100 μm, an increase of the low-frequency limit of the real part of the impedance and a decrease of the high-frequency phase angle were however observed experimentally as the electrolyte film thickness decreases. This specific behavior, in disagreement with the classical linear diffusion theory, was explained by the potential distribution existing in the thin-layer cell and was modeled using an original transmission line. In a very low-frequency range (lower than 1 mHz), an additional time constant was also evidenced. In consistency with previous work of Gabrielli et al.1 on microelectrodes, this feature was ascribed to the radial contribution of diffusion processes existing within a thin-layer cell.

Effect of Prussian Blue on Organic Sulfur of Coal in Aqueous Medium

This study is an attempt to desulfurize organic sulfur from coal samples with ferric hexacyanoferrate (II), Fe4 [Fe(CN)6], as the desulfurization agent. Effect of temperature, particle size and concentration of ferrocyanide ion on desulfurization from the coal samples has been investigated. The temperature and stirring time are the most important parameters for the level of desulfurization of organic sulfur. Removal of organic sulfur content increased continuously with increasing temperature from 298 to 368 K. The organic sulfur removal rate sharply increases from 10 min to 30 min stirring time. After 30 min, it reaches a value of plateau. Particle size between −100 mesh and −200 mesh slightly affects the amount of organic sulfur removal. Gradual increase in the concentration of ferric hexacyanoferrate (II) raised the magnitude of desulfurization, but at higher concentration, the variation is not significant.

Preparation of polypyrrole films containing ferrocyanide ions deposited onto thermally pre-treated and untreated iron substrate: Application in the electroanalytical determination of ascorbic acid

A polypyrrole containing ferrocyanide ions Fe(CN) 6 3− (FCN) as doping anions were prepared by anodic electropolymerization onto iron and onto thermally pre-treated iron electrodes, in an aqueous solution containing pyrrole, potassium hexacyanoferrate (K 4Fe(CN) 6) and potassium tetraoxalate (C 4H 3KO 8). The electrochemical behaviour of these modified electrodes was studied by cyclic voltammetry method. The electrostatic ability of these modified electrodes (PPy/FCN/Fe and PPy/FCN/Fe 3O 4/Fe) was demonstrated towards the oxidation of ascorbic acid (H 2A). The results show that Fe(CN) 6 3− anions incorporated into the PPy matrix improve the electrocatalytic activity of these films. The (PPy/FCN/Fe 3O 4/Fe) modified electrode showed greater ability and redox electroactivity than the (PPy/FCN/Fe) modified electrode and than the unmodified Fe electrode. It has been found that under optimum pH condition (pH 7), the oxidation of ascorbic acid at the surface of PPy/FCN/Fe 3O 4/Fe occurs at a potential about 200 mV less positive than at PPy/FCN/Fe and at Fe surfaces. The catalytic oxidation peak current showed a linear dependence on the ascorbic acid concentration and a linear calibration curve was obtained in the range 0.5–9 mM of ascorbic acid with a correlation coefficient of 0.9994 and good sensitivity (0.24 μA/μM). The detection limit (2 σ) was determined and found to be equal to 0.15 mM.

Desulfurization of Organic Sulfur from Lignite by an Electron Transfer Process

This study is an attempt to desulfurize organic sulfur from lignite samples with ferrocyanide ion as the electron transferring agent. Effect of temperature, particle size and concentration of ferrocyanide ion on desulfurization from the lignite samples has been investigated. The desulfurization process has been found to be continuous and gradually increases with increase of temperature from 298 to 368 K. The particle size has no significant impact on sulfur removal from the lignite samples. Particle size has no profound impact on the amount of sulfur removal. The desulfurization reaction has been found to be dependent on the concentration of potassium ferrocyanide. Gradual increase in the concentration of potassium ferrocyanide raised the magnitude of desulfurization, but at a higher concentration, the variation is not significant.

First coupling between a LINAC and FT-IR spectroscopy: The aqueous ferrocyanide system

New results on the aqueous ferrocyanide system at neutral pH are presented here using the coupling of a 10 MeV LINAC with infrared spectroscopy. Seconds after irradiation, we observe a decrease of the Fe ( CN ) 6 4 - ferrocyanide ion concentration. Hydroxopentacyanoferrate(III) as well as hexacyanoferrate(III) ions are formed. After a 1500 Gy irradiation, we observe de-aquation of the former species, leading to the latter with a characteristic time of about 410 s and reduction of ferricyanide into ferrocyanide ions with a rate constant of 3 mol −1 dm 3 s −1. Berlin green is also detected when the irradiation dose is greater than 2500 Gy.

Photochemical synthesis of Prussian blue film from an acidic ferricyanide solution and application

We describe a novel photochemical method to synthesize compacted Prussian blue (PB) film from an acidic ferricyanide solution. The key step is the photochemical reduction of ferricyanide ion to ferrocyanide ion that subsequently coordinates with the free ferric ion dissociated from the ferricyanide in acidic medium to form Prussian blue on the illuminated electrode surface. The prepared PB film electrode shows high electrocatalytic activity towards the reduction of hydrogen peroxide and the amperometric responses show a linear dependence on the concentration of hydrogen peroxide in a range of 1.0 × 10 −6 to 1.2 × 10 −3 M with a detection limit down to 4 × 10 −7 M. The present photochemical method provides a simple and promising route for the local fabrication of patterned molecular magnets, ion-selective sensors, and electro- or photochromic devices.

Synthesis and characterization of inherently conducting polymers by using Scanning Electrochemical Microscopy and Electrochemical Quartz Crystal Microbalance

Understanding ion transport processes in electrically conducting polymers is very important in the light of possible application of these materials in chemical or biosensors. In this work we have studied the ion transport in the electrochemically synthesized inherently conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) induced by the redox switching of the polymer. Mass changes during the synthesis and redox switching of the film have been monitored in-situ by Electrochemical Quartz Crystal Microbalance (EQCM). By doping the conducting polymer film with electroactive materials such as ferrocyanide ions (FCN) the release of the different oxidation state species during the voltage cycling of the polymeric film could be monitored on-line by Scanning Electrochemical Microscopy (SECM). Direct evidence of the exchange capability of Fe(CN) 6] 4−/3− anions entrapped in PEDOT/FCN film with Cl − anion from the solution and doping levels were found by computing the experimental data provided by SECM and EQCM techniques. In addition, SECM measurements showed that during reduction of the PEDOT/FCN films only the release of [Fe(CN) 6] 4− ion occurs.

Oxidation of Triethylamine by Ferricyanide Ions in the Presence of Sodium Hydroxide and Potassium Hydroxide

The rate of the oxidation of triethylamine by ferricyanide ions in sodium hydroxide or potassium hydroxide solutions has been determined spectrophotometrically at 25℃. Analysis of the kinetic data indicates that the hydroxide ion does not appear in the rate law. Strong retardation of the oxidation of triethylamine, caused by the addition of ferrocyanide ions, has been observed. A plausible mechanism is suggested, and a suitable rate law, congruent with the experimental observations, has been derived.

A new precipitation technique provides evidence for the permeability of Casparian bands to ions in young roots of corn (Zea mays L.) and rice (Oryza sativa L.)

ABSTRACTUsing an insoluble inorganic salt precipitation technique, the permeability of cell walls and especially of endodermal Casparian bands (CBs) for ions was tested in young roots of corn (Zea mays) and rice (Oryza sativa). The test was based on suction of either 100 µm CuSO4 or 200 µm K4[Fe(CN)6] into the root from its medium using a pump (excised roots) or transpirational stream (intact seedlings), and subsequent perfusion of xylem of those root segments with the opposite salt component, which resulted in precipitation of insoluble brown crystals of copper ferrocyanide. Under suction, Cu2+ could cross the endodermis apoplastically in both plant species (although at low rates) developing brown salt precipitates in cell walls of early metaxylem and in the region between CBs and functioning metaxylem vessels. Hence, at least Cu2+ did cross the endodermis dragged along with the water. The results suggested that CBs were not perfect barriers to apoplastic ion fluxes. In contrast, ferrocyanide ions failed to cross the mature endodermis of both corn and rice at detectable amounts. The concentration limit of apoplastic copper was 0.8 µm at a perfusion with 200 µm K4[Fe(CN)6]. Asymmetric development of precipitates suggested that the cation, Cu2+, moved faster than the anion, [Fe(CN)6]4–, through cell walls including CBs. Using Chara cell wall preparations (‘ghosts’) as a model system, it was observed that, different from Cu2+, ferrocyanide ions remained inside wall‐tubes suggesting a substantially lower permeability of the latter which agreed with the finding of an asymmetric development of precipitates. In both corn and rice roots, there was a significant apoplastic flux of ions in regions where laterals penetrated the endodermis. Overall, the results show that the permeability of CBs to ions is not zero. CBs do not represent a perfect barrier for ions, as is usually thought. The permeability of CBs may vary depending on growth conditions which are known to affect the intensity of formation of bands.

Electrochemical incineration of oxalic acid: Reactivity and engineering parameters

Mass transfer measurements were carried out to test a disk-shaped parallel-plate electrochemical cell, based on a new design. The impinging-jet-cell concept, confined between parallel plates, was adapted to a configuration with one central inlet and several peripheral exit sections, leading to more effective hydrodynamics within the cell. Measurements of mass transfer coefficient were performed using the limiting diffusion current technique based on ferro-cyanide ion oxidation, and overall mass transfer coefficients were correlated to Reynolds numbers ranging from 30 to 200.

An artificial electron donor supported catalytic cycle of Pseudomonas putida cytochrome P450 cam

Putidaredoxin (PdX), the physiological effector of cytochrome P450 cam (P450 cam), serves to gate electron transfer into oxy-P450 cam during the catalytic cycle of the enzyme. Redox-linked structural changes in PdX are necessary for the effective P450 cam turnover reaction. PdX is believed to be difficult to be replaced by an artificial electron donor in the reaction pathway of P450 cam. We demonstrate that the catalytic cycle of wild-type P450 cam can be supported in the presence of an artificial reductant, potassium ferrocyanide. Upon rapid mixing of ferrocyanide ion with P450 cam, we observed an intermediate with spectral features characteristic of compound I. The rate constant for the formation of compound I in the presence of ferrocyanide supported reaction cycle was found to be comparable to the ones observed for H 2O 2 supported compound I formation in wild-type P450 cam, but was much lower than those observed for classical peroxidases. The results presented in this paper form the first kinetic analysis of this intermediate for an artificial electron-driven P450 cam catalytic pathway in solution.

Interactions between Multivalent Ions and Exponentially Growing Multilayers: Dissolution and Exchange Processes

The interactions between multivalent ions (small ions or polyelectrolytes) and two exponentially growing polyelectrolyte multilayers, namely, (HA-PLL)(n)() and (HA-PAH)(n)() films, are investigated (HA = hyaluronic acid, PLL = poly-l-lysine, PAH = poly(allylamine)). Ferrocyanide and ferricyanide ions are used as small ion probes. The most striking finding is that, even though these two ions differ only by one charge unit, the ferrocyanide ions induce a partial dissolution of both multilayers whereas these films remain stable in the presence of ferricyanide ions. The dissolution process of (HA-PLL)(n)() films is more rapid than that of (HA-PAH)(n)() films, indicating a stronger interaction between HA and PAH compared to HA and PLL. This is confirmed by polyelectrolyte exchange experiments: when an (HA-PLL)(n)() multilayer film is put into contact with a PAH solution, PLL is quantitatively exchanged with the PAH chains and transformed into an HA-PAH film, whereas an (HA-PAH)(n)() multilayer remains stable in the presence of a PLL solution.

Layer by Layer Self-Assembled Polyelectrolyte Multilayers with Embedded Phospholipid Vesicles Obtained by Spraying: Integrity of the Vesicles

In a previous paper (Michel, M.; Vautier, D.; Voegel, J.-C.; Schaaf, P.; Ball, V. Langmuir 2004, 20, 4835), we showed that phospholipid vesicles can be incorporated into poly(glutamic-acid)/poly(allylamine) (PGA/PAH) multilayered polyelectrolyte films built by the alternated dipping of a surface in polyanion and polycation solutions. AFM imaging, quartz crystal microbalance, and ellipsometry suggested that the vesicles remain intact when adhering on the surface. In the present paper, we show that such films can also be realized by spraying both the polyelectrolyte solutions and the vesicles onto the surface. Using such vesicles filled with ferrocyanide ions, we prove by cyclic voltammetry that the sprayed vesicles remain intact when embedded in the multilayers. We show that multilayers containing two distinct layers of intact vesicles separated by several polyanion/polycation bilayers can also be constructed. Polyelectrolyte multilayers containing layers of phospholipid vesicles could act as reservoirs for drug or other biologically active molecules in controlled release bioactive coatings.

Application of wavelet transform in pulsed ultrasonic modulation voltammetry

In this study, wavelet transform was employed to achieve the different current components in pulsed ultrasonic modulation voltammetry. It was found that the pulsed sonovoltammograms could be decomposed into wavelet approximations and wavelet details by projecting wavelet transform on the signals in question. Since wavelet approximations with a certain scale parameter may retain the waveform of the original signal, the current components resulted from ultrasound “on” and “off” in pulsed sonovoltammograms could be separated at a certain scale parameter in multiplying wavelet approximation. With this method, the current components corresponding to pulse-on and pulse-off can be recorded separately without the external data acquisition system used in general modulation voltammetric measurements. The current difference between the two states was found to be proportional to the concentration of the electroactive species. The analytical usefulness of this approach was exploited for determination of ferrocyanide ion at sub-micromolar concentrations.