Complexing reactions in the Ni(II)-5-methyl-4-amino-3-thiooxo-1,2,4-triazapentene-1-methanal and Ni(II)-5-methyl-4-amino- 3-thiooxo-1,2,4-triazapentene-1-propanone triple systems

Complexing processes in the Ni^II-TTA-methanal (A) and Ni^II-TTA-propanone (B) triple systems (TTA–5-methyl-4-amino-3-thiooxo-1, 2, 4-triazapentene-1) in ethanol solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix have been studied. In the Ni^II-TTA- methanal system, formation of Ni^II oligomeric coordination compounds in which metal chelate cycles are connected by–H₂C–O–CH₂–structural groups, takes place. In the Ni^II-TTA-propanone triple system, formation of only Ni^II complexes with TTA takes place. No complexing process in the triple systems in nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix was found.     

Determination of hexacyanoferrate based on its catalytic influence on the oxidation of p-phenylenediamines by iron(III)

Summary Both hexacyanoferrate(III) and hexacyanoferrate(II) catalyze the oxidation of p-phenylenediamines by iron(III)_aq. The rate of this reaction in the presence of a sample with an unknown amount of hexacyanoferrate is compared with the reaction rate of solutions containing well defined concentrations of this substance. In this way, hexacyanoferrate can be determined photometrically down to <10^–9 mol/l. Although this procedure is very sensitive, the analysis can be performed with a simple photometer. Absorbance changes >0.2 can easily be obtained in 1 cm cuvettes, even at extremely small concentrations of hexacyanoferrate, because it is not an absorbance proportional to the concentration of hexacyanoferrate but rather the formation rate of p-semiquinonediimine which enables the quantitative determination of hexacyanoferrate.     

Laccase Based Synergistic Electrocatalytical System

Bioelectrodes employing the conversion of N‐substituted phenothiazine/hexacyanoferrate(II) and N‐substituted phenoxazine/hexacyanoferrate(II) that act as synergistic substrates were built using graphite electrode and recombinant laccase. The response of the bioelectrodes to low reactive substrate (hexacyanoferrate(II)) increases 2.9–97 times in presence of high reactive phenothiazine or phenoxazine mediator. The sensitivity of the bioelectrodes reaches 0.5–14.3 A/M?cm². To background a scheme of bioelectrodes action the kinetics of laccase‐catalyzed synergistic substrates oxidation was investigated in homogenous solution. A satisfactory agreement of experimentally determined rate constants and calculated using parameters of bioelectrocatalytical system confirms the scheme of bioelectrodes action.     

Kinetics and mechanism of osmium(VIII)-catalyzed oxidation of 1,4-thioxane by alkaline hexacyanoferrate(III)

The kinetics of oxidation of 1,4-thioxane (1,4-oxathiane) by alkaline K₃Fe(CN)₆ have been studied in the presence of Os^VIII as catalyst. The reaction is first order in hexacyanoferrate(III) and Os^VIII. The order in thioxane and OH^– is zero. While added salts and ethanol have a negligible effect on the oxidation rate, K₄Fe(CN)₆ retards it. On the basis of kinetic evidence, a mechanism has been proposed.     

Amperometric determination of formaldehyde via the hexacyanoferrate(III) -coupled dehydrogenase reaction

An enzymatic method with amperometric detection was developed for the determination of formaldehyde. Formaldehyde is first oxidized by reaction with NAD⁺ in the presence of formaldehyde dehydrogenase. The resulting NADH is then oxidized by hexacyanoferrate(III) in the presence of diaphorase to produce hexacyanoferrate(II). The anodic current generated by oxidation of the hexacyanoferrate(II) at the surface of a glassy carbon working electrode, held at a potential of 0.40 V vs. an Ag/AgCl reference electrode, is measured. The effects of solution conditions are examined and a linear relationship between rate of current change and formaldehyde concentration is obtained from 0.01 to 0.5 μg ml^?1 with a correlation coefficient of 0.9998. The relative standard deviation for the proposed method is 6.4% at 0.01 μg ml^?1 formaldehyde and 0.88% at 0.5 μg ml^?1.     

A new approach for the synthesis of K-free nickel hexacyanoferrate

A Ni, Al hydrotalcite-like compound (Htlc) has been proven an useful host material for an alternative synthesis of a K⁺-free mixed hexacyanoferrate Ni_1.5Fe^III(CN)₆, which is very difficult to obtain in bulk. The first stage of the procedure consists in the intercalation of hexacyanoferrate(III) inside the Htlc structure. The intercalated Htlc has been treated with a NiNO₃ solution. The obtained material has been characterized by XRD, XAS Raman and FT-IR spectroscopy. The voltammetric response of the compound obtained after the complete solubilization of the Htlc host shows a typical fingerprint of nickel hexacyanoferrate material with a very low level of potassium. Elemental analysis confirmed the absence of K⁺ and thus the occurrence of K⁺-free nickel hexacyanoferrate (14% yield).     

Kinetics of Hydrogen Peroxide Decomposition in Guaiacol Solution, Catalyzed by Hexacyanoferrate(II)

The kinetics of hydrogen peroxide decomposition in a guaiacol solution, catalyzed by potassium hexacyanoferrate(II), were studied. The reaction mainly follows the pathway of guaiacol hydroxylation. The reaction order is 1 with respect to H₂O₂, 0.5 with respect to hexacyanoferrate, and from 0.4 to 0 with respect to guaiacol (the latter parameter decreases with increasing guaiacol concentration). The apparent activation energy is 105 kJ mol^{- 1}. A kinetic scheme of the process was proposed. An expression consistent with the experiment was obtained for the rate of hydrogen peroxide decomposition in the presence of guaiacol, catalyzed by hexacyanoferrate(II).     

Kinetics and mechanism of palladium (II) chloride catalyzed oxidation of allyl alcohol by potassium hexacyanoferrate (III)

A kinetic study of the oxidation of allyl alcohol by potassium hexacyanoferrate (III) in the presence of palladium (II) chloride is reported. The reaction was observed by measuring the disappearance of the potassium hexacyanoferrate (III) spectrophotometrically. The reaction is first order with respect to allyl alcohol and palladium (II) chloride, inverse second order with respect to [Cl^?], and zero order with respect to potassium hexacyanoferrate (III). The rate is found to increase linearly with hydroxyl ion concentration.     

Yeast-based carbon paste bioelectrode for ethanol

An amperometric bioelectrode for primary alcohols based on the incorporation of yeasts into the carbon paste matrix is reported. The response is based on the activity of alcohol dehydrogenase in yeasts. The intimate contact between the biocatalytic and sensing sites results in short response times. The addition of a redox-mediating hexacyanoferrate (III) ion greatly facilitates the detection of the enzymatically produced NADH. The effects of operating potential, carbon paste composition, concentration of coenzyme or redox mediator and other parameters are explored for optimum analytical performance. The dynamic properties of this electrode are exploited for detection in flow-injection systems, with a detection limit of 2 × 10^?6 M (9 ng) of ethanol. The relative standard deviation for repetitive injections of a 1× 10^?3 M ethanol solution over a 100-min period is 2.8%. Applicability to alcoholic beverages is illustrated. The trend in sensitivity toward different alcohols is in agreement with the known biospecificity of yeast alcohol dehydrogenase.     

Solid Membranes of Copper Hriacyanoferrats (III) as Thallium (I) Sensitive Electrode

Abstract

Solid membranes of copper hexacyanoferrate (III) in Areldite are evaluated as thallium (I) sensitive electrode. The membrane electrode gave a linear near Normstian response to thallium (I) ions in the concentration range 10^?1 - 5 × 10^?4 M and can be used to estimate T1 (I) down to 10^?4 M. The responses of the electrode is fast and steady potentials are obtained in less than a minute. The same membrane has been used over a period of six months without any appreciable drift in potential. The electrode can also be used satisfactory in partially non-aqueous media and in presence of a number of interfering ions. It is superior to the existing T1(I) solid membrane electrodes as it can function in alkaline range also.     

Spectrophotmetric Determination of Trace Amounts of Formaldehyde

Abstract

Colourless silver (I)-gelatin complex is quantitatively reduced by formaldehyde to yellov/ silver sol in the presence of 10 U NaQH at room temperature. The determination of formaldehyde at microgram level is possible at 440 nm in the presence of methanol, ethanol, acetone and also in the presence of various reducing agents. The molar absorptivity of the 4 -1 -1 solution is 2.16 × 10 lit mol cm with a relative standard deviation of 0.105%, a confidence limit (for 10 determinations)of 0.9 ± 0.0006 and Sandell sensitivity 1.38 × 10 μg cm^?2.     

Determination of Paracetamol by a Flow Injection-Spectrophotometric Method

Abstract

A flow injection-spectrophotometric determination of paracetamol is reported. The procedure is based on the oxidation of the analyte with potassium hexacyanoferrate (III) and reaction of the N-(hydroxyphenyl)-p-benzoquinonimine produced with phenol; both reactions are carried out at 80 × 1°C and in aqueous ammoniacal solution. Concentrations of paracetamol in 0.25-30 ppm range are determined; relative standard deviations are 0.4% (n=40).Injection rate 26 samples/h.The influence of foreign species and the determination of paracetamol in several pharmaceutical formulations are also reported.     

Synthesis of Some 2-(3-Alkyl/aryl-5-trifluoromethylpyrazol-1-yl)-4-(coumarin-3-yl)thiazoles as Novel Antibacterial Agents

Abstract

Herein, we describe a one-pot synthesis of some novel 2-(3-alkyl/aryl-5-trifluoromethylpyrazol-1-yl)-4-(coumarin-3-yl)thiazoles (6) involving the reaction of 3-alkyl/aryl-5-hydroxy-5-trifluoromethyl-4,5-dihydropyrazole-1-thiocarboxamides (3) with 3-bromoacetylcoumarins (5) in the presence of sodium carbonate in ethanol. Reaction of 3 with 5 in the absence of sodium carbonate, however, resulted in the formation of 2-(3-alkyl/aryl-5-hydroxy-5-trifluoromethyl-4,5-dihydropyrazol-1-yl)-4-(coumarin-3-yl)thiazoles, which were subsequently dehydrated to 6 by refluxing in ethanol in the presence of sodium carbonate. The structure of the synthesized compounds (6) was confirmed by infrared (IR), mass, ¹H NMR, and ¹³C NMR spectra and elemental analysis data. Newly synthesized compounds (6) showed moderate to good activity against Gram-positive bacteria.     

Amperometric Determination of Inositol Based on Electrocatalytic Oxidation on a Glass Carbon Electrode Modified by Nickel Hexacyanoferrate Films

Abstract

A novel method to determinate inositol based on the electrocatalytic oxidation of inositol on the surface of a nickel hexacyanoferrate (NiHCF)–modified electrode was reported. The determination of inositol can be performed in the range of 1.0×10^?4 to 5.8×10^?3 mol/L with a detection limit of 5.0×10^?5 mol/L.     

Preparation of Thallium Hexacyanoferrate Film and Mixed‐Film Modified Electrodes with Cobalt(II) Hexacyanoferrate

Thallium hexacyanoferrate films have been prepared from various aqueous electrolyte solutions using consecutive cyclic voltammetry. The cyclic voltammograms recorded the direct deposition of thallium hexacyanoferrate films from the mixing of Tl³⁺ and [Fe(CN)₆]^3? ions from solutions of seven cations: Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, H⁺, and Tl⁺. An electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the thallium hexacyanoferrate films. The thallium hexacyanoferrate film shows a single redox couple with a formal potential between +0.6 V and +1.2 V, and shows a cation effect (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and Tl⁺). A mixed film and a two‐layered modified electrodes composed of a thallium hexacyanoferrate film with cobalt(II) hexacyanoferrate film were prepared.     

Formation of ultra-thin prussian blue layer on carbon steel that promotes adherence of hybrid polypyrrole based protective coating

Electrodeposition of well-adhering polypyrrole-based hybrid films containing hexacyanoferrate(II,III) anions from neutral solutions of pyrrole and potassium hexacyanoferrate(II) on medium carbon (0.48% C) steel has been described. The resulting polypyrrole coatings that are doped with hexacyanoferrate(II,III) anions show protective properties against pitting corrosion of carbon steel substrates in strongly acidic media containing chlorides (0.1 mol dm^–3 HCl + 0.4 mol dm^–3 NaCl). Polypyrrole acts as a stable host matrix for inorganic anions. The presence of negatively charged species (hexacyanoferrates) in the polymer backbone tends to block the access of pitting-causing anions (chlorides) to the surface of steel. The Fe(CN)₆^3-/4– anions existing in the vicinity of steel substrate stabilizes its surface by forming an overcoating in the form of sparingly soluble metal hexacyanoferrate, mostly Prussian blue (PB), microstructures. It has been demonstrated that by applying cyclic voltammetry and X-ray photoelectron spectroscopy, the presence of traces of free cyanide anions promotes the formation of PB on carbon steel surface which results in increasing the adherence of polypyrrole-based films to the metallic substrate. Morphology of the protective composite films is also addressed.Dedicated to Prof. G. Horanyi on the occasion of his 70th birthday     

Preparation and characterization of a new carbon paste electrode based on ketotifen–hexacyanoferrate

A new type of carbon paste electrode (CPE) was made using ketotifen fumarate (C₂₃H₂₃NO₅S; an antiasthmatic/antianaphylactic drug) and hexacyanoferrate. This electrode was constructed using an acidic solution of ketotifen fumarate and potassium hexacyanoferrate. For this purpose, ketotifen fumarate was dissolved in acidic solution (pH 1) and hexacyanoferrate was added by agitation, resulting in ketotifen–hexacyanoferrate (Ket–HCF) precipitate. The obtained precipitate was separated and introduced into carbon paste. The electrochemical behavior of Ket–HCF CPE was studied by cyclic voltammetry. A modified electrode shows one pair of peaks with surface-confined characteristics, with a 0.1-M phosphate buffer as supporting electrolyte. The effects of pH, alkali metal cations, and anions of supporting electrolytes on the electrochemical characteristics of modified electrodes were studied. The diffusion coefficients of hydrated K⁺ in film (D), the transfer coefficient (α), and the transfer rate constant for electrons (k _s) were determined.     

Removal of60Co and134Cs from radioactive process waste water by flotation

The removal of¹³⁴Cs and⁶⁰Co from radioactive process waste water using cetyl pyridinium chloride (CPC) as a collector and cobalt(II) hexacyanoferrate(II) as a precipitant for⁶⁰Co and sorbent (ion exchanger) for¹³⁴Cs was intensively investigated and the best removal conditions could be established. The results indicate that under the optimum conditions removals higher than 96% and 97% could be achieved for Co(II) and Cs(I), respectively. Cobalt(II) hexacyanoferrate(II) was found to have high affinity for cesium and can preferentially remove it in presence of relatively high amounts of other alkali or alkaline earth cations. A two-stage flotation process was successfully tested for the removal of both Cs(I) and Co(II) from waters containing both cations.     

Synthesis,structural characterization and catalytic potential of oxidovanadium(IV) and dioxidovanadium(V) complexes with thiazole-derived NNN-donor ligand

Reaction between the tridentate NNN donor ligand, (E)-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)benzo[d]thiazole (HL), and V₂O₅ in ethanol gave a new vanadium(V) complex, [VO₂L] (1), while the similar reaction by using [V^IVO(acac)₂] as the metal source gave two different types of crystals related to compounds [VO₂L] (1) and [V^IVO(acac)L] (2). The molecular structures of the complexes were determined by single-crystal X-ray diffraction and spectroscopic characterization was carried out by means of FT-IR, UV–vis and NMR experiments as well as elemental analysis. The oxidovanadium(IV) and dioxidovanadium(V) species were used as catalyst precursors for olefin oxidation in the presence of hydrogen peroxide (H₂O₂) as an oxidant. Under similar experimental conditions, the presence of 1 resulted in higher oxidation conversion than 2.     

Determination of aliphatic aldehydes in aqueous solution by chemiluminescence measurements

The determination of aliphatic aldehydes (5 × 10^-6 — 2.5 × 10^-4 mol) in aqueous solution was achieved by inhibition of the luminol chemiluminescence induced by hydrogen peroxide in the presence of potassium hexacyanoferrate(III).