Ferrocyanide Concentration Research Articles

Uptake of ferrocyanide in willow and poplar trees in a long term greenhouse experiment.

Phytoremediation of sites contaminated with iron cyanides can be performed using poplar and willow trees. Poplar and willow trees were grown in potting substrate spiked with ferrocyanide concentrations of up to 2,000mgkg(-1) for 4 and 8weeks respectively. Soil solution and leaf tissue of different age were sampled for total cyanide analysis every week. Chlorophyll content in the leaves was determined to quantify cyanide toxicity. Results showed that cyanide in the soil solution of spiked soils differed between treatments and on weekly basis and ranged from 0.5 to 1,200mgl(-1). The maximum cyanide content in willow and poplar leaves was 518mgkg(-1) fresh weight (FW) and 148mgkg(-1) FW respectively. Cyanide accumulated in the leaves increased linearly with increasing cyanide concentration in the soil solution. On the long term, significantly more cyanide was accumulated in old leaf tissue than in young tissue. Chlorophyll content in poplar decreased linearly with increasing cyanide in the soil solution and in leaf tissue, and over time. The inhibitory concentration (IC50) value for poplars after 4weeks of exposure was 173mgl(-1) and for willow after 8weeks of exposure-768mgl(-1). Results show that willows tolerate much more cyanide and over a longer period than poplars, making them very appropriate for remediating sites highly contaminated with iron cyanides.

Electrochemical sensing of hepatocyte viability

We investigated the use of amperometric and chronoamperometric methods with a double mediator system and screen-printed electrodes (SPEs) for the electrochemical sensing of hepatocyte viability. Cell counts were determined based on measuring cellular respiration via interaction of electroactive redox mediators. The oxidation currents of chronoamperometric measurement were proportional to the concentrations of ferrocyanide which was produced via interaction of cellular respiration, succinate and ferricyanide. The integrated oxidation charges increased linearly with the density of the cultured primary rat hepatocytes over a range of 1 × 10(5) to 5 × 10(5) cells per well (slope = 1.98 (±0.08) μC per 10(5) cells; R(2) = 0.9969), and the detection limit was 7600 (±300) cells per well based on S/N = 3. Each density of cells was cultured in triple replicates and individual cell samples were evaluated. The results of the cytotoxic effect of the chronoamperometric method are comparable to those of the tetrazolium-based colorimetric assay. The chronoamperometric method with ferricyanide and succinate mediators is an efficient, alternative method for assessing the viability of primary hepatocytes which can be completed in 20 min. Succinate did not provide an efficient electron shuttle between cytosolic respiratory redox activity of cancer cells and extracellular ferricyanide, an effect that may be useful for distinguishing hepatocarcinoma cells from healthy hepatocytes.

Electroless Plating Copper on SiC Particles

Abstract. SiCp/Cu composites because of their excellent performance in the aerospace, carrying tools in the field with a wide range of applications, but the poor interfacial bonding limits its application. To improve the interfacial bonding between SiCp and copper, we use Copper Plating on SiCp particles coated handle. The results show that the optimal process parameters for electroless plating copper on SiC particle is followed as:CuSO4•5H2O concentration of 30g/L, EDTA•2Na concentration of 1g/L, potassium ferrocyanide concentration of 2g/L, potassium sodium tartrate concentration 105g/L, plating temperature is 50°C, plating time was 40 minutes.With the increase of the pH from 10 to 13, the uniform dense electroless plating copper exists on SiC particle. With increase of temperature of electroless plating bath, the smooth copper coating on SiC particle can be obtained at 50°C.

Preparation of Iron Ferrocyanide-Supported Nanofiber Membrane for Purification of Cesium-Contaminated Water

The earthquake in northeastern Japan that occurred on March 11, 2011 brought about the nuclear accident, resulting in the detection of radioactive cesium in soil and water over a wide region around Fukusihma. In this study, with the aim of the establishment of an effective method for removing cesium from water contaminated with cesium, the functionalized membrane with large cesium adsorption capacity per unit mass was prepared by combining nanofibers having a large specific surface area with iron ferrocyanide having a high selectivity for cesium adsorption. The nanofiber membrane made of polyacrylonitrile (PAN) was used as a base material of the functionalized membrane. Nanofiber membranes were immersed in the dispersions of iron ferrocyanide with various concentrations and pH values. After taking it out, it was dried at various temperatures and then non-immobilized iron ferrocyanide was completely removed through cleaning. As a result of the evaluation of completed affinity membranes, the amount of iron ferrocyanide immobilized by the nanofiber membrane increased significantly with the increase in the iron ferrocyanide concentration but subsequently showed a tendency to decrease rapidly, resulting in a distinct maximum at the iron ferrocyanide concentration of 3 wt%. And, the supported amount of iron ferrocyanide to the nanofiber membrane increased as pH became lower. Moreover, it was found that as high temperature as possible without exceeding the glass transition temperature of PAN was optimal as a drying temperature of prepared affinity membrane.

Trapping of redox-mediators at the surface of Chlorella vulgaris leads to error in measurements of cell reducing power

The reduction of the redox mediator ferricyanide, [Fe(CN)6](3-), by a range of algal and bacterial species, is frequently measured to probe plasma membrane ferrireductase activity or to quantify the reducing power of algal/bacterial biofilms and suspensions. In this study we have used rotating disk electrochemistry (RDE) to investigate the reduction of ferricyanide by the model organism Chlorella vulgaris. Importantly, we have seen that the diffusion limited current due to the oxidation of ferrocyanide, [Fe(CN)6](4-), at the electrode decreased linearly as C. vulgaris was added to the solution, even though in a pure ferrocyanide solution the algae are not able to reduce the mediator further and are simply spectator 'particles'. We attribute this effect to trapping of ferrocyanide at the cell surface, with up to 14% of the ferrocyanide missing from the solution at the highest cell concentration. The result has important implications for all techniques that use electrochemistry and other concentration dependent assays (e.g. fluorescence and colourimetry) to monitor ferrocyanide concentrations in the presence of both biofilms and cell suspensions. Analyte trapping could lead to a substantial underestimation of the concentration of reduced product.

Dual Photonic-Electrochemical Lab on a Chip for Online Simultaneous Absorbance and Amperometric Measurements

A dual lab on a chip (DLOC) approach that enables simultaneous optical and electrochemical detection working in a continuous flow regime is presented. Both detection modes are integrated for the first time into a single detection volume and operate simultaneously with no evidence of cross-talk. The electrochemical cell was characterized amperometrically by measuring the current in ferrocyanide solutions at +0.4 V vs gold pseudoreference electrode, at a flow rate of 200 μL min(-1). The experimental results for ferrocyanide concentrations ranging from 0.005 to 2 mM were in good agreement with the values predicted by the Levich equation for a microelectrode inside a rectangular channel, with a sensitivity of 2.059 ± 0.004 μA mM(-1) and a limit of detection (LoD) of (2.303 ± 0.004) × 10(-3) mM. Besides, optical detection was evaluated by measuring the absorbance of ferricyanide solutions at 420 nm. The results obtained therein coincide with those predicted by the Beer-Lambert law for a range of ferricyanide concentrations from 0.005 to 0.3 mM and showed an estimated LoD of (0.553 ± 0.001) × 10(-3) mM. The DLOC was finally applied to the analysis of L-lactate via a bienzymatic reaction involving lactate oxidase (LOX) and horseradish peroxidase (HRP). Here, the consumption of the reagent of the reaction (ferrocyanide) was continuously monitored by amperometry whereas the product of the reaction (ferricyanide) was recorded by absorbance. The DLOC presented good performance in terms of sensitivity and limit of detection, comparable to other fluidic systems found in the literature. Additionally, the ability to simultaneously quantify enzymatic reagent consumption and product generation confers the DLOC a self-verifying capability which in turn enhances its robustness and reliability.

Ion-induced cell sheet detachment from standard cell culture surfaces coated with polyelectrolytes

Polyelectrolyte multilayers (PEMs), formed by alternating layer-by-layer deposition of polyanions and polycations, are an ideal substrate for controlling cellular adhesion and behavior. In the present study we propose a simple mechanism for the controlled detachment of C(2)C(12) myoblasts cell sheets from PEMs consisting of poly(l-lysine) and hyaluronic acid with a topmost layer of fibronectin. The multilayers were deposited on two standard cell culture surfaces: glass and polystyrene. Adding a low concentration of nontoxic ferrocyanide to the cell culture medium resulted in erosion of the polyelectrolyte multilayer and rapid detachment of viable cell sheets. Additional Quartz Crystal Microbalance and Atomic Force Microscopy measurements indicated that the detached cells retained their extracellular matrix and that no polyelectrolyte molecules remained bound to the cell sheets. The dissolution of polyelectrolyte multilayers by multivalent ions is a promising approach to cell sheet engineering that could potentially be used for regenerative medicine.

Electron transfer kinetics of cytochrome c immobilized on a phenolic terminated thiol self assembled monolayer determined by scanning electrochemical microscopy

In the present manuscript, the electrochemical behavior of cytochrome c (cyt-c) immobilized onto a phenolic terminated self assembled monolayer (SAM) on a gold electrode is investigated using cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The tunneling electron transfer (ET) rate constant between the immobilized protein and the underlying electrode surface, and also the bimolecular ET rate constant between the immobilized protein and a probe has been obtained using approach curves that were obtained by SECM. The approach curves were recorded at different substrate overpotentials in the presence of various concentrations of ferrocyanide as a probe and various surface concentrations of cyt-c; then the standard tunneling ET and bimolecular rate constants are obtained as 3.4 ± 0.3 s−1 and (2.0 ± 0.5) × 107 cm3 mol−1 s−1, respectively.

Treatment of Cyanide Bearing Water/Wastewater by Plain and Biological Activated Carbon

Comparative study of biodegradation and adsorption alone with simultaneous adsorption and biodegradation (SAB) process was carried out along with a brief review of the processes. Adsorption and SAB studies were carried out in plain and Pseudomonas putida immobilized granular activated carbon (GAC), whereas biodegradation was conducted with suspended cultures of P. putida. P. putida used iron cyanide as the sole source of nitrogen at an initial pH of 7.0 and temperature of 30 °C. At an initial iron(II) cyanide concentration of 100 mg/L, removal efficiencies of cyanide by adsorption, biodegradation, and SAB were found to be 81.5%, 78.2%, and 96.7%, respectively. The initial ferrocyanide concentrations of 50−350 mg CN−/L were taken for the study. The microbes adopted to grow at maximum cyanide concentration were harvested, and their ability to degrade cyanide were measured in both biodegradation and SAB. The removal efficiency of biologically activated granular activated carbon (BAC) was found better as compared to that of plain GAC. It was also found that the SAB process is more effective than adsorption and biodegradation alone.

Assimilation and physiological effects of ferrocyanide on weeping willows

Uptake, assimilation, and toxicity of exogenous iron cyanide complexes in plants were investigated. Pre-rooted young weeping willows (Salix babylonica L.) were exposed to hydroponic solutions spiked with potassium ferrocyanide at 24.0 ± 1°C for 192 h. Transpiration rates, chlorophyll contents, soluble protein, and activities of superoxide dismutases (SOD), catalase (CAT), and peroxidase (POD) of the plants were monitored to determine toxicity to the cuttings. Of all selected parameters, POD activity in leaves was the most sensitive bioindicator to the increase of ferrocyanide concentrations. Between 11% and 19% of applied ferrocyanide in the solutions was removed by willows at the end of the incubation period. Only small amounts of ferrocyanide were recovered in different parts of the plant materials. Mass balance analysis showed that more than 90% of the ferrocyanide taken up from the hydroponic solutions was assimilated by plants. The assimilation of ferrocyanide by plants showed a dose-dependent manner. These findings suggest that phytoremediation of ferrocyanide-contaminating wastewater and soils can be possible for the environmental cleaning up.

Minimally invasive spatial and temporal concentration profiling within working glucose biosensors

The time-dependent evolution of analyte during the operation of working glucose biosensors has been profiled using a carbon fibre microelectrode (CFE). A simple procedure for the fabrication of minimally invasive CFE probes (<8 μm maximum diameter) is described. By positioning the CFE at well-defined distances from a working biosensor surface it has been possible to track the concentration of ferrocyanide, generated in the enzymatic assay for glucose, as a function of space and time. The results indicate that on the timescale of operation of typical glucose biosensors, the enzyme-mediated oxidation of glucose only occurs to a significant extent in a thin layer close to the sensor surface. In much of the analyte volume the reaction is negligible, contrary to present consensus.

Nanodiamond film with ‘ridge’ surface profile for chemical sensing

Abstract A nanodiamond film with ‘ridge’ surface morphology was grown on highly doped n-type silicon substrate by microwave plasma enhanced chemical vapor deposition (MPECVD) using a H 2 /CH 4 /N 2 gas mixture. The nanodiamond electrode was electrochemically characterized by cyclic voltammetry using various concentrations of ferrocyanide in a background of 0.1 M KCl. The results show a wide working potential window of ~ 3 V, quasi-reversible kinetics with a high signal to noise S/B ratio. The peak current increases linearly with increasing concentration of ferrocyanide. Also, the peak current varies linearly with the square root of scan rate indicating planar diffusion dominated mass transport. The nanodiamond electrode exhibits excellent structure stability and electrochemical behavior without any surface pretreatment, indicating it is an excellent candidate for electrochemical sensing.

Study of Ion Transfer Across the Liquid−Liquid Interface Coupled to Electrochemical Redox Reaction at the Pt Electrode with a Three-Electrode Potentiostat

The ion transfer across the liquid−liquid interface coupled to electrochemical redox reaction at the Pt electrode was investigated simultaneously with a three-electrode potentiostat in combination with cyclic voltammetry. The approach involves using a small aqueous droplet containing a redox couple supported on a platinum electrode and immersed into an organic electrolyte solution. Both electron and ion transfer processes can be observed at separate interfaces for the first time. The effects of concentrations of the redox couple on ion transfer indicate that the overall electrochemical process, proceeding as a coupled electron−ion transfer reaction, is controlled by the electron transfer across the Pt/W interface and the electron-transfer reaction is the drive force of ion transfer across the L/L interface. In addition, for the first time, a new oscillation phenomenon has been observed directly, which is related to the L/L interface, to concentration of ferrocyanide and to potential scan range. The oscill...

Catalytic‐Kinetic Determination of Silver(I) Using Hexacyanoferrate(II) and 2,4,6‐Tripyridyl‐1,3,5‐Triazine(TPTZ)

AbstractA highly sensitive and selective kinetic spectrophotometric method is proposed for the determination of silver in nanogram quantities. The method is based on catalytic activity of silver(I) in enhancing the green colour formation between potassium ferrocyanide and 2,4,6‐tripyridyl‐1,3,5‐triazine (TPTZ) which is otherwise a very slow reaction at pH 2.0. The absorbance spectrum of the green coloured solution in presence of silver showed two peaks of almost equal intensity one at 405 nm and another at 600 nm. At both the wavelengths the absorbance of the experimental solution increased proportionally with the amount of silver(I) in the range 5 – 410 ng mL‐1 and 10 – 610 ng mL‐1 respectively. Other experimental conditions like pH, reagent concentration, ferrocyanide concentration and effect of time for obtaining maximum reaction rate were optimized. The molar absorptivity, Sandell's sensitivity, detection limit, determination limit and relative standard deviation (n = 8) were determined as 1.57 × 106 L mol‐1 cm‐1, 0.065 ng cm‐2, 1.6 ng mL‐1, 4.8 ng mL‐1 and 0.81 % respectively. The effect of various diverse ions on the determination of silver was studied. The method was applied for the determination of silver in alloys, biological samples, effluents, real water and in ayurvedic medicines.

Ferrocyanide − a novel catalyst for oxymyoglobin oxidation by molecular oxygen

A comparative study of the rates of ferrocyanide-catalyzed oxidation of several oxymyoglobins by molecular oxygen is reported. Oxidation of the native oxymyoglobins from sperm whale, horse and pig, as well as the chemically modified (MbO(2)) sperm whale oxymyoglobin, with all accessible His residues alkylated by sodium bromoacetate (CM-MbO(2)), and the mutant sperm whale oxymyoglobin [MbO(2)(His119-->Asp)], was studied. The effect of pH, ionic strength and the concentration of anionic catalyst ferrocyanide, [Fe(CN)(6)](4-), on the oxidation rate is investigated, as well as the effect of MbO(2) complexing with redox-inactive Zn(2+), which forms the stable chelate complex with functional groups of His119, Lys16 and Asp122, all located nearby. The catalytic mechanism was demonstrated to involve specific [Fe(CN)(6)](4-) binding to the protein in the His119 region, which agrees with a high local positive electrostatic potential and the presence of a cavity large enough to accommodate [Fe(CN)(6)](4-) in that region. The protonation of the nearby His113 and especially His116 plays a very important role in the catalysis, accelerating the oxidation rate of bound [Fe(CN)(6)](4-) by dissolved oxygen. The simultaneous occurrence of both these factors (i.e. specific binding of [Fe(CN)(6)](4-) to the protein and its fast reoxidation by oxygen) is necessary for the efficient ferrocyanide-catalyzed oxidation of oxymyoglobin.

Influence of a soil enzyme on iron-cyanide complex speciation and mineral adsorption

Cyanide is commonly found as ferrocyanide [Fe(II)(CN)(6)](-4) and in the more mobile form, ferricyanide [Fe(III)(CN)(6)](-3) in contaminated soils and sediments. Although soil minerals may influence ferrocyanide speciation, and thus mobility, the possible influence of soil enzymes has not been examined. In a series of experiments conducted under a range of soil-like conditions, laccase, a phenoloxidase enzyme derived from the fungi Trametes versicolor, was found to exert a large influence on iron-cyanide speciation and mobility. In the presence of laccase, up to 93% of ferrocyanide (36-362ppm) was oxidized to ferricyanide within 4h. No significant effect of pH (3.6 and 6.2) or initial ferrocyanide concentration on the extent or rate of oxidation was found and ferrocyanide oxidation did not occur in the absence of laccase. Relative to iron-cyanide-mineral systems without laccase, ferrocyanide adsorption to aluminum hydroxide and montmorillonite decreased in the presence of laccase and was similar to or somewhat greater than that of ferricyanide without laccase. Laccase-catalyzed conversion of ferrocyanide to ferricyanide was extensive though up to 33% of the enzyme was mineral-bound. These results demonstrate that soil enzymes can play a major role in ferrocyanide speciation and mobility. Biotic soil components must be considered as highly effective oxidation catalysts that may alter the mobility of metals and metal complexes in soil. Immobilized enzymes should also be considered for use in soil metal remediation efforts.

A novel “coral” carbon microprobe with and without N 2 incorporation

Abstract “Coral”-type microstructure carbon films, with and without N 2 incorporation, were grown on sharpened tungsten microprobes by plasma enhanced chemical vapor deposition (PECVD) using H 2 /CH 4 /N 2 and H 2 /CH 4 gas mixtures, respectively. The electrochemical behaviors of the coral-type carbon coated tungsten microprobe, characterized by various concentrations of ferrocyanide in a background of 0.1 M KCl, show excellent structural stability with similar microstructure before and after prolonged analysis without the need of surface pretreatment. The microprobes exhibit quasi-reversible kinetics with high signal-to-noise S / B ratio. The N 2 incorporated microprobe shows a slightly wider potential window, no surface adsorption of the analyte and higher sensitivity as compared to the sample without nitrogen incorporation. Furthermore, the wide potential window of ∼ 3 V is very good as compared to boron-doped diamond electrodes which are ∼ 3.5 V. This well behaved; broad electrochemical behavior and the simple fabrication method make the “coral” carbon film microprobe an excellent candidate for electrochemical sensing.

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.

Signal enhancement for electrochemical detection at glassy carbon electrode modified with phenyl layer

Glassy carbon (GC) electrode was modified with phenyl layer using electrochemical reduction of benzenediazonium tetrafluoroborate. The phenyl layer on GC inhibits direct electron transfer of ferrocyanide but allows for facile electrode kinetics of hydroxymethylferrocene (HMF) in solution-phase. Based on this selective electrochemical discrimination of phenyl layer, a voltammetric signal enhancement for the detection of HMF was studied at phenyl-modified GC electrode in phosphate buffer (pH = 7.2) solution containing ferrocyanide as a sacrificial species. The current amplification ratio (R) was found to be linear to the ferrocyanide concentration ranging from 0.1 to 10 mM.

EIS study of the redox reaction of Fe(CN) 63−/4− at poly(3,4-ethylenedioxythiophene) electrodes: influence of dc potential and cOx: cRed ratio

Abstract The electron transfer between the ferri/ferrocyanide redox couple and poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes has been investigated by electrochemical impedance spectroscopy (EIS). Different thicknesses of the conducting polymer films were investigated (i) at a constant concentration of ferrocyanide in the solution at different applied dc potentials and (ii) at the open circuit potential with different ratios of Fe(CN)63−:Fe(CN)64− in the solution. PEDOT was prepared by galvanostatic electropolymerization on platinum electrodes from aqueous solutions containing 0.01 M 3,4-ethylenedioxythiophene (EDOT) and 0.1 M poly(sodium 4-styrenesulfonate) (NaPSS) as the supporting electrolyte. All impedance spectra were obtained in aqueous solutions with 0.1 M KCl as the supporting electrolyte at dc potentials, where the polymer is in the oxidized state. The EIS data were fitted to an equivalent electrical circuit resembling the Randles' circuit, where the double layer capacitance is replaced by the bulk redox capacitance and the associated transport impedance of the conducting polymer. The same potential and thickness dependence of the charge transfer resistance (Rct) were obtained both (i) by varying the concentration ratio of the redox species in the solution and (ii) by applying different potentials at a constant concentration of ferrocyanide. The potential dependence of k0 calculated from Rct indicates that the conducting polymer influences the rate of electron transfer for the ferri/ferrocyanide redox couple.