Lanthanum complexation with reagents of the arsenazo III group on the solid phase of fibrous ion exchangers

Color reactions of lanthanum with reagents of the arsenazo III group on the solid phase of fibrous materials filled with an ion exchanger are studied. Substrates and reagents of various types, sorption and complexation conditions, and effects of some concomitant components are investigated. The most pronounced analytical effect is observed upon lanthanum sorption on disks with an anion exchanger containing iminodiacetate ANKB-50 groups followed by complexation on the solid phase with arsenazo III or arsenazo M in 0.05 M HCl. The reaction with arsenazo III is characterized by the lowest detection limit (5 ng/mL), and the reaction with arsenazo M is most selective.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 4, 2005, pp. 378–383.Original Russian Text Copyright © 2005 by Savvin, Shvoeva, Dedkova.     

Complex formation reaction of the iron(III) hydroxo dimer with periodate ion

The kinetics and mechanism of the ligand substitution reaction between Fe(2)(OH)(2)(4+) and periodate ion has been studied. This process is unique among the reactions of the iron(iii) hydroxo dimer because the initial rate is second-order with respect to Fe(2)(OH)(2)(4+). The formation of a bi- and a tetranuclear complex, Fe(2)(OH)(2)(H(4)IO(6))(3+) and Fe(4)(OH)(4)(H(4)IO(6))(7+), is proposed. Comprehensive fitting of the kinetic data was used to show that the proposed model, which is very similar to earlier models used with other inorganic oxoanions, gives a reasonable interpretation of all observations. It is shown that the lifetime of Fe(2)(OH)(2)(H(4)IO(6))(3+) is relatively long and it can open a pathway to form oligomeric and less soluble products at higher initial concentrations. The speciation of aqueous periodate ion solution was also studied and it is proposed that the tetrahedral form, IO(4)(-), is less dominant over the octahedral form, H(4)IO(6)(-), than previously thought.     

Structure of iron(III) ion and its complexation with thiocyanate ion in N,N-dimethylformamide

Complexation of iron(III) with thiocyanate ions has been calorimetrically and spectrophotometrically investigated in N,N-dimethylformamide (DMF) containing 0.4 mol/dm(3) (C(2)H(5))(4)NClO(4) or 1 mol/dm(3) NH(4)ClO(4) as a constant ionic medium at 25 degrees C. Calorimetric titration data were well explained in terms of the formation of [Fe(SCN)(n)]((3-n)+) (n = 1-5), and their formation constants, reaction enthalpies and entropies were determined. Electronic spectra of individual iron(III) thiocyanato complexes were also determined. The stepwise thermodynamic quantities changed monotonously, i.e. DeltaG degrees (1) < DeltaG degrees (2) < DeltaG degrees (3) < DeltaG degrees (4), < DeltaG degrees (5), DeltaH degrees (1) > DeltaH degrees (2) > DeltaH degrees (3) > DeltaH degrees (4) > DeltaH degrees (5), DeltaS degrees (1) > DeltaS degrees (2) > DeltaS degrees (3) > DeltaS degrees (4) > DeltaS degrees (5). This suggests that no extensive desolvation occurred at any step of complexation. On the basis of these thermodynamic quantities, it is postulated that the [Fe(SCN)(n)]((3-n)+) (n = 1-5) complexes have a six-coordinate octahedral structure as well as the [Fe(dmf)(6)](3+) ion, the octahedral structure of which has been confirmed by the EXAFS (extended X-ray absorption fine structure) method.     

Complexation of vanadium(IV) with organic reagents on the solid phase of fibrous ion exchangers according to diffuse reflectance and EPR data

Diffuse reflectance and EPR spectroscopic data are reported for the formation of vanadium complexes with the organic reagents (ORs) sulfochlorophenol S (SCP) and pyridylazoresorcinol (PAR) on the solid phase of polyacrylonitrile fiber filled with the cation exchanger KU-2 or the anion exchanger AV-17 or A-5. The effects of the order of sorption of the reaction components, sorption conditions, and the V: OR ratio on the complexation process are discussed. The characteristics of the complexes obtained on the solid phase and in solution are compares. Both M : OR = 1 : 1 and M : OR = 2 : 1 SCP complexes can form on the solid phase without involving any croups of the matrix. PAR forma a 1 : 1 complex involving groups of the A-5 matrix.     

Complex formation of iron (III) with eriochrome cyanine r

The complex formation of iron(III) with the trisodium salt of 5-[α-(3-carboxy-5-methyl-4-oxo-2,5-cyclohexadien-1-ylidene)-2-sulfobenzyl]-3-methylsalicylic acid (eriochrome cyanine R) was studied by spectrophotometry. The pure tetrabasic acid of the ligand (H₄ER) was prepared and used in the investigation. In the pH range 2.7–4.2 three complexes were detected: a ring-formed dimer Fe₂(ER)₂, Fe₂(ER) and Fe(ER) ; the absolute stability constants (at an ionic strength of 0.1 M and at room temperature (20 ± 3°)) were log k = 37.9, log k = 22.5 and log k = 17.9, respectively.     

Complex formation of iron (III) with chrome azurol s

The complex formation of iron(IIl) with 3”-sulpho-2”,6”-dichloro-3,3'-dimethyl-4'-hydroxy-fuchson-5,5'-dicarboxylic acid (chrome azurol S) was studied by spectrophotometric, conductometric and potentiometric methods. The pure tetrabasic acid of the ligand was prepared from the impure trisodium salt (commercially availalile), and the dissociation constants of the ligand were redetermined. At 20° ± 1° and in the presence of 0.10 M potassium chloride the dissociation constants were: pk₁ < 0.0, pk₂ = 2.25 ± 0.05, pk₃ = 4.71 ± 0.03 and pk₄ = 11.81 ± 0.03.In the pH range 2–4, four complexes were detected (the absolute stability constants at 20° ± 5° and at an ionic strength of 0.10 M are given in parentheses) : a ring-formed dimer complex [Fe(H₂O)₂]₂Ch₂^2- (log k_2,2 = 36.2); a monomer of composition [Fe(H₂O)₄]HCh or [Fe(H₂O)₄]HCh^- (the absolute stability constant was calculated as log k_1,1 = 15.6 for the latter composition); a complex [Fe(H₂O)₄]₂Ch²⁺ (log k_3.1=20.2) and, finally, a complex of composition [Fe(H₂O)₂]H_xCh₂^x-5 (the value of x being unknown). In addition, hydroxo complexes of the dimer were formed at higher pH values.     

Sorption properties of new nitrogen-containing wood-based ion exchangers with respect to gold(III) ions

Sorption properties of new nitrogen-containing wood-based ion exchangers with respect to gold(III) ions were examined in relation to the metal ion concentration in solution, pH of medium, and sorption temperature and time. The rate-limiting steps in the process were identified. The mechanism of sorption of aurate ions from solutions was considered in relation to their acidity.     

Complex formation equilibria in iron(III)-L-alanine system

Summary Complex formation in iron(III)-L-alanine solutions was studied by emf glass electrode and spectrophotometric measurements, in 0.5 mol dm ^–3 (Na)NO₃ medium, at 25 ° C. In the concentration range 0.5 [Fe]₀ 20.0, 5.0 [Ala]₀ 1000.0 (mmol dm^–3) and 1.0 -log [H⁺] 3.5; {[Ala]/[Fe] = 10:1-100:1| the equilibria in the title system were explained by the model including the species FeHL, FeL, Fe(OH)L, Fe₂(OH)₂L₂ (where HL denotes L-alanine) and several hydrolytic products. The stability constants of complexes are given. The mechanism of formation and structure of complexes in solution is proposed.Abbreviations Ala alaninate ion - HAla alanine (zwitterion) - AlaH alanine (neutral) - H₂Ala⁺ alanine cation     

Effect of arsenate and phosphate ions on the adsorption and complexation of uranium(VI) with Arsenazo III on the solid phase of the ion exchanger PAN-EDE-10p fibrous anion exchanger

The effect of arsenate and phosphate ions on the adsorption and color reaction of uranium(VI) with Arsenazo III on the solid phase of a fibrous material filled with the EDE-10p anion exchanger was studied in different adsorption processes. We selected the optimum conditions for the system of U(VI)-AsO ₄ ^3? (H₂PO ₄ ^? )-PANV-EDE-10p-Arsenazo III and used this system for the adsorption-spectrophotometric determination of (0.03–0.3) 10^?3 M arsenate, (0.004–0.06) 10^?3 M phosphate, and 0.01–0.1 μg/mL uranyl ions.     

On the complex formation equilibria between iron (III) and sulfate ions

The equilibria have been investigated at 25 degrees C in 3 M NaClO4 using potentiometry, glass and redox Fe3+/Fe2+ half-cells, and UV optical absorptiometry. The concentration of the reagents was chosen in the intervals: 10(-4) < or = [Fe(III)] < or = 5.10(-3) M, 0.01 < or = [SO4(2-)]tot < or = 0.65 M. The value of [H+] was kept at 0.1 M or more to reduce the hydrolysis of the Fe3+ ion to less than 1%. Auxiliary constants, corresponding to the formation of Fe(II)-sulfate complexes and to the association of H+ with SO4(2-) ions, were taken from previous determinations. The experimental data could be explained with the equilibria [formula: see text] Equilibrium constants at infinite dilution, log beta 101 degrees = 3.82 +/- 0.17, log beta 102 degrees = 5.75 +/- 0.17 and log beta 111 degrees = 3.68 +/- 0.35, have been evaluated by applying the specific interaction theory.     

Determination of tungsten with iron(III) after reduction with mercury in thiocyanate medium

Tungsten(V) is formed by shaking for 2 min sodium tungstate solution in 0.4 M potassium thiocyanate-4M hydrochloric acid medium, with mercury. It is titrated with standard iron(III) solution. The thiocyanate present stabilizes W(V) to aerial oxidation and also acts as indicator. The W(V) can also be titrated potentiometrically in 7M hydrochloric acid, a tungsten wire electrode being used. Fe, Ni, Cr, Zr, Bi, Sb, Ce, Al, Pb, Ca and U do not interfere. Cu, V and As can be tolerated up to 5 mg. Co, Mo, Re, Nb and Mn interfere, but not in the potentiometric determination. The method is direct, simple, rapid, accurate and reproducible.     

Selective complex formation of saccharides with europium(III) and iron(III) ions at alkaline pH studied by ligand-exchange chromatography

At high pH, saccharides become negatively charged by deprotonation of one or several hydroxylic groups and they are highly and selectively retained by ligand-exchange chromatography. The systems consist of a sulphonated polystyrene strong cation exchanger in europium(III) or iron(III) form and sodium hydroxide as mobile phase. The degree of complex formation is dependent on solute character and concentration, metal ion and pH, the reaction being of second order as confirmed by breakthrough studies. Rapid desorption of the solutes is performed by the introduction of an acidic mobile phase. Monosaccharides, and especially sugar alcohols, are selectively retained by a column in Fe(III) form whereas all saccharides are strongly retained as Eu(III) complexes, e.g., the capacity factor for the breakthrough of 10 μM glucose, in 0.1 M NaOH as mobile phase, was ca. 3500 The systems are proposed to be highly selective for the analysis of sugars.     

Model studies on iron(III) ion affinity chromatography. II. Interaction of immobilized iron(III) ions with phosphorylated amino acids, peptides and proteins.

The chromatographic behaviour of phosphoamino acids, phosphopeptides and phosphoproteins and their non-phosphorylated counterparts was studied on Fe(III)-Chelating Sepharose and Fe(III)-Chelating Superose. The phosphorylated compounds, in contrast to their non-phosphorylated or dephosphorylated counterparts, adsorb to immobilized iron(III) ions at pH 5.5 and can be desorbed by an increase in pH. Phosphoamino acids were eluted at pH 6.5-6.7, whereas monophosphopeptides and phosphoprotamine eluted in the pH range 6.9-7.5. Molecules possessing clusters(s) of carboxylic groups are weakly retained (gamma-carboxyglutamic acid, Ala-Ser-Glu5) or bound (polyglutamic acid, beta-casein) to the immobilized iron(III) ions at pH 5.5. Dephosphorylated beta-casein was desorbed at pH 7.0, whereas for elution of native (non-dephosphorylated) beta-casein, phosphate buffer of pH 7.7 was required. The homopolymer of polyglutamic acid was desorbed in the pH range 6.0-6.3, whereas copolymers of glutamic acid and tyrosine require pH 7.0-7.3 or even phosphate buffer at pH 7.7 for elution.     

Hydrogen chloride absorption from the air with the fibrous ion exchangers FIBAN

Hydrogen chloride sorption from the air in a wide range of relative humidity and the concentration of the absorbing component was examined under dynamic conditions with fibrous anion exchanger FIBAN distinguishing by basicity and type of functional groups.     

Selective solid phase extraction and preconcentration of iron(III) based on silica gel-chemically immobilized purpurogallin

The immobilization of purpurogallin on the surface of amino group containing silica gel phase for the formation of a newly synthesized silica gel-bound purpurogallin (SGBP) is described. The surface modification was studied and evaluated by determination of the surface coverage value by both the elemental analysis and metal probe testing method, which was found to be 0.485 and 0.460 mmol g⁻¹, respectively. The metal sorption properties of SGBP were examined by a series of di- and tri-valent metal ions. The metal capacity values (mmol g⁻¹) for this series of metal ions were also determined under different buffer solutions (pH 1.0–6.0) as well as shaking times by the batch equilibrium technique. The results of this study confirmed the strong affinity and selectivity as well as the fast equilibration and interaction processes of SGBP and Fe(III) compared to the other tested metal ions. The reduction–oxidation process of iron(II)/iron(III) by SGBP was also studied and the results indicated only 2.1% reduction of iron(III) into iron(II). The selectivity incorporated into silica gel phase via the immobilization of purpurogallin was intensively studied for a several binary mixtures containing iron(III)—another interfering metal ion. The determined percentage extraction values of iron(III) from these mixtures were found to be in the range of 94–100%. The potential applications of SGBP as a selective solid extractor for iron(III) from natural tap water samples and real matrices were also studied and the results revealed good percentage extraction values of iron(III) (93.5−94.9±4.6−5.3%) of the spiked iron(III) in the acidified tap water samples as well as a high preconcentration factor of 500 was also established when SGBP was used as a selective solid phase extractor and preconcentration of iron(III) from acidified soft drink samples with percentage recovery values of (98.0−97.4±4.7−5.3%) of the spiked iron(III).     

Sorption-spectroscopy and test determination of uranium(VI) and iron(III) from a single sample on the solid phase of fiber materials filled with an AB-17 ion exchanger

Diffuse reflectance spectroscopy has been used for the study of the sorption of malonate and glycolate complexes of uranium(VI) and iron(III), present simultaneously in solution, onto the solid phase of fiber materials filled with an AB-17 anion exchanger. In the form of malonate complexes uranium(VI) is determined in 0.5 M HCl on substrate discs with immobilized Arsenazo III, while iron(III) is determined on substrate discs with potassium thiocyanate in 0.5 M HCl. The dependence of the analytical signals on the concentrations of U(VI) and Fe(III) is linear in the ranges 0.02–0.16 μg/mL; the detection limit is 0.01 μg/mL. The possibility of analysis of U(VI) and Fe(III) mixtures in ratio from 1: 5 to 5: 1 in the presence of 2-fold concentrations of Zr(IV), Th(IV), and Ti(IV), 5-fold concentrations of Bi(III), 10-fold concentrations of Cu(II), 20-fold concentrations of La(III), 100-fold concentrations of Ni(II) and Zn(II), and 200-fold concentrations of Co(II) and Ca(II) has been demonstrated. Standard color scales in the concentration range from 0.02 to 0.2 μg/mL have been used for the visual determination of uranium(VI) and iron(III).