Ferron Complexes Research Articles

Indirect Spectrophotometric Method for Determination of Methyldopa in Pure and Pharmaceutical Formulation

Sensitive and accurate spectrophotometric method for the assay of methyldopa (MeD) as pure form and in it is formulations. The method was centred on the oxidation of methyldopa drug with Fe+2ions. The free Fe+2 ions react with 4,7-diphenyl-1,10-phenanthroline chromogenic reagent. In the method, the formed Ferron complex is colorimetrically can be monitored at 533 nm versus reagent blank. The linear relationship between various MeD concentrations versus absorbance for each concentration was in the range of 0.25-2.5 μg.mL-1 with molar absorptivity 1.3272x105 L.mol-1.cm-1 for the method. The determination coefficient (R2) was found to be 0.9902, and the limit of detection (LOD) and limit of quantification(LOQ) were 0.011μg.ml-1and 0.036 μg.ml-1, respectively. The percent recovery from 99.84% to 102.40 %. The suggested procedure could be used for the estimation of MeD in dosage forms (two types of tablets from two companies) with satisfactory results.

Enhanced coagulation for TiO2-NPs removal by using a hybrid flocculant

A hybrid flocculant, PAC-CA, with the advantages of inorganic and organic flocculants, was prepared, and the coagulation behavior and floc characteristics of PAC-CA for removing titanium dioxide nanoparticles (TiO2-NPs) under different conditions were studied. The effects of monomer mass ratio, initiator concentration, hydroxyl aluminum ratio, reaction temperature, and polymerization time on the coagulation performance for TiO2-NP removal were studied. PAC-CA was characterized through SEM, FT-IR, TG-DSC, XRD, XPS, and Ferron complex colorimetric characterization. The characterization results showed that PAC-CA was successfully copolymerized using AlCl3, carboxymethyl chitosan, and acrylamide. The high content of Alb in PAC-CA helped improve the coagulation performance. When the dosage was 30 mg/L, the pH was 8, the stirring intensity was 200 s−1, and the settling time was 30 min, the optimal removal rates for TiO2-NPs and turbidity were 87.30% and 91.72%, respectively. Kaolin could effectively improve the TiO2-NP removal efficiency and promote the density and particle size of flocs. Humic acid exerted an inhibitory effect on coagulation efficiency with loose and small flocs.

Combination of cloud point extraction and flame atomic absorption spectrometry for preconcentration and determination of trace iron in environmental and biological samples

Abstract In the presented work, the conditions for cloud point extraction of iron from aqueous solutions using 7-iodo-8-hydroxyquinolin-5-sulphonic acid (Ferron) was investigated and optimized. The procedure is based on the separation of its ferron complex into the micellar media by adding the surfactant Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1.0 M HNO3 in methanol. Iron was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities, incubation time, temperature, viscosity, sample volume, and interfering ions were investigated. The effects of the matrix ions were also examined. The detection limits for three times the standard deviations of the blank for iron was 0.4 ng m L-1, enrichment factor of 19.6 and preconcentration factor of 30 could be achieved. The validity of cloud point extraction was checked by employing real samples including soil, blood, spinach, milk, meat, liver and orange juice samples using the standard addition method, which gave satisfactory results.In the presented work, the conditions for cloud point extraction of iron from aqueous solutions using 7-iodo-8-hydroxyquinolin-5-sulphonic acid (Ferron) was investigated and optimized. The procedure is based on the separation of its ferron complex into the micellar media by adding the surfactant Triton X-114. After phase separation, the surfactant-rich phase was dissolved with 1.0 M HNO3 in methanol. Iron was determined by flame atomic absorption spectrometry. Optimization of the pH, ligand and surfactant quantities, incubation time, temperature, viscosity, sample volume, and interfering ions were investigated. The effects of the matrix ions were also examined. The detection limits for three times the standard deviations of the blank for iron was 0.4 ng m L−1, enrichment factor of 19.6 and preconcentration factor of 30 could be achieved. The validity of cloud point extraction was checked by employing real samples including soil, blood, spinach, milk, meat, liver and orange juice samples using the standard addition method, which gave satisfactory results.

Extraction of molybdenum(V) as its ferron complex with trioctylamine in chloroform from a sulphuric acid medium

A simple, rapid, and highly selective method for the separation of molybdenum from a large number of elements of analytical importance has been developed. The method is based on the extraction of a Mo(V)-ferron (7-iodo-8-hydroxyquinoline-5-sulphonic acid) complex into trioctylamine-chloroform in a sulphuric acid medium using ascorbic acid as a reductant. Many elements such as Re(VII), W(VI), U(VI), Th(IV), Cr(III), Cr(VI), V(V), Ce(IV), Ru(III), Co(II), Ni(II), Mn(II), Fe(II), Fe(III), Cd(II), Mg(II), Cu(II), Al(III), Zn(II), Pb(II), Ag(I), and As(V) are not extracted under the conditions proposed and, thus, molybdenum can be easily separated without any interference. Sulphate, chloride, nitrate, phosphate, and oxalate anions have no effect on the extraction of molybdenum. However, zirconium and palladium interfere seriously. The ratio of Mo: ferron: TOA in the extracted species is found to be 1: 1: 3 using Job’s method of continuous variations. This value has been further confirmed by the mole-ratio method.

Adsorptive Square‐Wave Voltammetry for the Analysis and Speciation of Complexes of Cd(II)‐Ferron

AbstractThe theory of adsorptive stripping square‐wave voltammetry (SWV) for relatively low ligand concentrations is employed to determine the reduction mechanism of Cd(II)‐ferron complexes accumulated on a static mercury drop electrode at different pH values. The electrochemical behavior of ferron molecules indicated that the adsorptive concentration of Cd(II) is possible in solutions with 3.5<pH<11, providing a wide pH range where the interference of other ligands present in real samples would be not so critical. Cyclic voltammetry experiments were also performed for the purpose of comparison. Fitting between experimental and theoretical square‐wave voltammograms shows that the prevailing species at the reaction layer coincide with the equilibrium bulk distribution. The simulation procedure indicated that the electrochemical rate constants of Cd(II)‐ferron complexes varied from (6±1) s−1 to (0.17±0.01) s−1 for solutions analyzed at pH 3.9 and 10.8, respectively. Changes at the surface concentrations are discussed considering the ligand to complex ratios at the electrode surface and at the solution bulk. From this analysis it is possible to infer that the oxidized metal species are produced in the electrolytic solution instead of on the electrode surface.

The dimer bis(μ-8-hydroxy-7-iodoquinoline-5-sulfonato-κ3N,O:O′)bis[triaquamagnesium(II)] tetrahydrate

In the title crystal structure, [Mg2(C9H4INO4S)2(H2O)6]·4H2O, the Mg2+ ion has a distorted octahedral coordination geometry, surrounded by N and O atoms of the oxine ring (bidentate chelation), one of the O atoms of a sulfonate group and three water mol­ecules. The inversion-related ligands, water mol­ecules and Mg2+ ions form a cage-like dimer. These dimers are further cross-linked by O—H⋯O hydrogen bonds. The title compound is isomorphous with earlier reported ferron complexes of Co, Ni and Zn.

Adsorptive square-wave voltammetry applied to study the reduction mechanism of Cu–sulfoxine and Cu–ferron complexes

The reduction mechanisms of Cu(II) in solutions with the quinoline derivatives sulfoxine (Sox) and ferron (Fer) are studied by the simulation of their experimental square-wave voltammetric curves. Sox and Fer form very stable complexes with Cu(II) that can be accumulated on mercury electrodes by adsorption. Cathodic linear scan stripping voltammetry was performed for comparison purposes. The reaction schemes consider the reduction of an adsorbed oxidized complex with a ligand/metal stoichiometric ratio higher than that of the product. The remaining ligand may remain adsorbed or be released in solution. The fits between experimental and theoretical curves reveal the prevalence of the adsorbed species Cu(Sox) 2 2− and Cu(Fer) 2 2− at pH 6.4 and 5.3, respectively, which are the same as predicted by the distribution species diagram for the bulk of the solution. At these pH values, Cu(Sox) 2 2− and Cu(Fer) 2 2− complexes present essentially the same E p and electrochemical rate constants k s=(1.3±0.1) s −1, and thus the same effective stability constants. The dependence of differential peak currents on the logarithm of the frequency describes the so-called quasi-reversible maximum ( f max). The frequency of this maximum is lower for solutions with high pH, indicating that the charge transfer rate is decreased when the stability of the complexes is enlarged. The f max value is related to the ligand/complex concentration ratio and it is applied to the estimation of k s. Changes at the surface concentrations were evaluated considering the ligand to complex ratios at the electrode surface and at the solution bulk.

Combination of solid phase extraction and flame atomic absorption spectrometry for differentiated analysis of labile iron (II) and iron (III) species

The labile iron(II) and iron(III) species are complexed directly in the sample solution with 1,10 phenanthroline and ferron (8-hydroxy-7-iodoquinoline-5-sulfonic acid), respectively. The complexes thus formed are mutually adsorbed and separated by solid phase extraction. The direct determination of iron(III) and iron(II) species with flame atomic absorption spectrometry (FAAS) follows the elution of the iron(III)-ferron complex adsorbed by an anion-exchange and an iron(II)-phenanthroline complex adsorbed by a non-polar RP-18 phase. In the case of indirect determination, the iron(II)-phenanthroline complex that passes through the anion-exchange phase, is measured, and the content of iron(III) is calculated by the difference of the iron(II) and the total iron content. A direct determination with this method has been applied to the iron species analysis in wine samples and the results are compared with those obtained for the determination with adsorptive stripping voltammetry (ASV) as reference method.

Extractive-spectrophotometric determination of tin as Sn(II)-ferron complex

Tin(II) forms a yellow coloured complex with ferron which can be extracted into tribenzylamine-chloroform solution from dilute hydrochloric acid medium. Tin is determined spectrophotometrically by measuring the absorbance at 390 nm. Beer's law is valid up to 7 μg Sn/ml with a sensitivity of 0.02 μg Sn/cm2. Chromium, manganese, iron, nickel, cobalt, copper, zinc, lead, magnesium, titanium, thorium, uranium and vanadium do not interfere. The method is quite simple and useful; its applicability has been tested by the analysis of synthetic samples and an alloy sample of gun metal.

A selective spectrophotometric method for determination of copper with ferron

A selective spectrophotometric determination of copper is based on extraction of the copper—ferron complex with tribenzylamine in chloroform at low acidity, and measurement of the absorbance of the yellow extract at 410 nm. Beer's law is found to hold up to 8 μg/ml copper concentration. Of 30 elements tested, only molybdenum interferes. The ratio copper:ferron:tribenzylamine in the extracted species is 1:2:2.

Effect of cationic surfactant on the formation of ferron complexes

In the spectrophotometric determination of aluminium and iron with ferron (7-iodo-8-quinolinol-5-sulphonic acid, H 2L), the addition of cationic surfactants greatly improves the linearity of the calibration curve and widens the useful pH range. The effect of cetyltrimethylammonium chloride (CTMAC) on the stepwise stability constants ( K 1, K 2 and K 3) of the ferron complexes of aluminium and iron (ML +, ML − 2 and ML 3− 3) and on the acid-dissociation constants ( K a1 and K a2) of ferron has been studied in connection with the role of the surfactant. CTMAC greatly increases the value of K 3 while exerting little effect on K 1 and K 2, thus rendering ML 3− 3 the predominant species even at very low concentration of free L 2−. It also has some effect on the acid-dissociation constants of ferron, but sometimes it acts to decrease the free L 2− concentration. At is therefore concluded that the improvements due to addition of surfactant should be attributed to the increased K 3 value. The presence of surfactant micelles is not essential, because the surfactant has a favourable effect when present at well below its critical micelle concentration, and because the continuous variations plots show a peak at a point corresponding to the composition M: L: Q (Q = cationic surfactant) = 1:3:3.

The spectrophotometric determination of vanadium after extraction as vanadium(III) ferronate by tribenzylamine

Vanadium(III) obtained by dithionite reduction of vanadium(V) can be extracted as its ferron complex with tribenzylamine in chloroform from 0.05 M sulphuric acid. Vanadium (0–5 μg ml -1) is determined spectrophotometrically at 430 nm with a sensitivity of 0.0028 μg V cm -2. Al(III), Co(II), Ni(II), Fe(II, III), Hg(II), Si(IV), Be(II), Mg(II), Ca(II), Sr(II), Ba(II), Cr(VI, III), W(VI), Zn(II), U(VI), Mn(II). Pb(II), Cu(II), Cd(II) and Th(IV) do not interfere; only Mo(VI), Ti(IV), Zr(IV). Bi(V) and Sn(II) interfere. A single determination takes only 7 min. The extracted complex is V III (R-3H.TBA) 3 where R = C 9H 4O 4NSI. The method is satisfactory for the determination of vanadium in steels, alum and other samples without preliminary separations.

Spectrophotometric determination of aluminium with ferron and a quaternary ammonium salt

The reproducibility of the ferron method for aluminium has been greatly improved by the addition of cetyltrimethylammonium chloride (CTMAC). The improvement is attributed to reduction of the reagent blank and increased stability of Al(ferron) 3− 3. The aluminium—ferron complex formed in the presence of CTMAC has an absorption peak at 385 nm. The interference from iron can be eliminated by application of a correction based on measurement at two wavelengths.

Studies on the ferron complexes of molybdenum(V)

It was reported [1] that molybdenum(V) gives an orange-yellow coloured complex with ferron at about pH 2, but no further study seems to have been made with regard to the extractability and composition of this complex. Continuing our earlier work[2] we report on their properties.

Studies on the ferron complexes of molybdenum(VI)

Molybdenum(VI) and ferron combine in 0·2 N acid medium to give a yellow product which can be extracted quantitatively into cyclohaxanol. Spectrophotometric investigations reveal that the complex in the aqueous phase has molybdenum(VI) and ferron in 1:1 ratio while the extracted species is Mo.Ferron 2 3 cyclohaxanol. The formation constants and the free energies of formation of the complexes have been calculated. A photometric method was developed based on the complexation and extraction. Iron(III) copper(II), vanadium(V) and tungsten(VI) interfere. Iron(III) can be masked with pyrophosphate. The tolerance limits for the other three are given. The optimum range with minimum error following Beer's law is 3·5–15· 0 μ/g of molybdenum per ml.