Chromaticity characteristics of iron (II, III) complexes with 1-nitroso-2-naphthol-3,6-disulfonic acid

Optimal conditions for the complexation of iron(II, III) with 1-nitroso-2-naphthol-3,6-disulfonic acid in two buffer solutions and the reduction of iron(III) with ascorbic acid or hydroxylamine were found by spectrophotometry and chromaticity measurements. Chemical analytical and chromaticity characteristics of complexes in solutions were determined. It was shown that two complexes formed depending on the oxidation state of iron. Molar coefficients of the chromaticity functions were 20 to 30 times higher than molar absorption coefficients. The complexes exhibited abnormal light absorption maxima (710–720 nm) among the known 1-nitroso-2-naphthol-3,6-disulfonates and were chemically inert, which offers promise for analytical purposes.     

Adsorption-photometric determination of iron using silica with nitroso-R salt and nitroso-N salt functional groups

Adsorbents based on silica sequentially modified by polyhexamethylene guanidine and nitroso-R salt or nitroso-N salt are proposed for the preconcentration and adsorption-photometric determination of iron. It is shown that these adsorbents quantitatively recovered Fe(III) at pH 3.5–4.0 and Fe(II) at pH 4.5–7.0. In the adsorption of Fe(III) and Fe(II), intensely colored green complexes formed on the adsorbent surface. Based on the absence of signals in EPR spectra, it was concluded that iron in the oxidation state +2 was included into surface complexes with nitroso-R salt or nitroso-N salt. When Fe(III) interacted with nitroso-R salt or nitroso-N salt immobilized on the adsorbent surface, it was reduced to Fe(II). Diffuse reflection spectra of the surface complexes of iron(II) were broad bands with maxima at 720 and 710 nm. Procedures of the adsorption-photometric determination of iron in natural waters and snow samples were developed with the limit of detection of 0.05 μg of iron per 0.2 g of the adsorbent.     

H-point standard addition method--first derivative spectrophotometry for simultaneous determination of palladium and cobalt

H-point standard addition method (HPSAM) has been applied for simultaneous determination of palladium and cobalt in trace levels, using disodium 1-nitroso-2-naphthol-3, 6-disulphonate (nitroso-R salt) as a selective chromogenic reagent. Palladium and cobalt in the neutral pHs form red color complexes with nitroso-R in aqueous solutions and making spectrophotometric monitoring possible. Simultaneous determination of palladium and cobalt were performed by HPSAM--first derivative spectrophotometry. First derivative signals at the two pairs of wavelengths, 523 and 589 nm or 513 and 554 nm were monitored with the addition of standard solutions of palladium or cobalt, respectively. The method is able to accurately determine palladium/cobalt ratio 1:10 to 15:1 (wt/wt). Accuracy and reproducibility of the determination method on the various amounts of palladium and cobalt known were evaluated in their binary mixtures. To investigate selectivity of the method and to ensure that no serious interferences were observed the effects of diverse ions on the determination of palladium and cobalt were also studied. The recommended procedure was successfully applied to real and synthetic cobalt or palladium alloys, B-complex ampoules, a palladium-charcoal mixture and real water matrices.     

Spectrophotometric Determination of Iron and Cobalt in Super Alloys

The quantitative analysis of iron and cobalt in super alloys has been studied. 1,-10-Phenanthroline and nitroso-R salt provide the chromophores for iron(II) and cobalt(II), respectively. The possibility of applying these photometric methods to a relatively complex substance, such as a super alloy, has been evaluated on the bases of precision and accuracy. The absorbance characteristics of metal complexes and the possible interference from foreign ions have also been carefully investigated. The presence of a high concentration of Ni results in a reducation of the amount of 1,10-phenanthroline available for the formation of ferroin complexes while Mo does not have this effect. The analytical methods have been applied to the super alloys, Inconel 718, Hastelloy X, and Inconel X-750. The modified 1,10-phenanthroline photometric method and the standard nitroso-R salt photometric method give high accuracy and good precision. This illustrates the analytical applicability of these reagents to super alloys.     

Use of the mathematical apparatus of two-component spectrophotometry for the simultaneous catalymetric determination of two anions

Previously studied reactions of aluminum(III) with Xylenol Orange and of cobalt(III) with nitroso-R salt in weakly acidic solutions were proposed for the simultaneous catalymetric determination of carbonate and borate ions and carbonate and phosphate ions, respectively. It was demonstrated that the mathematical apparatus of two-component spectrophotometry is suitable for processing the results of analysis.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 7–10.Original Russian Text Copyright © 2005 by Mikhailova, Belikov, Blank.     

Synthesis and Investigation of Geometrical Isomerism of Trinitro(aminoacidato)amminecobaltate(III) Complex Salts

Synthesis of a new class of coordination compounds of cobalt(III) with amino acids (glycine, alanine, α-amino-butyric acid and norvaline), i.e., trinitro(aminoacidato)-amminecobaltate(III) salts, M[CoNH₃Am(NO₂)₃], is described. The synthesis consists in the action of amino acid alkali salts on the Erdmann salt or peripheral isomer of trinitrotriamminecobalt(III). The same compounds were also obtained by direct synthesis, i.e., by hydrogen peroxide oxidation of cobalt(II) to cobalt(III) in the presence of the corresponding ligands. The peripheral configuration of the complexes obtained was determined by chemical and physical methods (electronic and PMR spectroscopy). The compounds are intermediates formed in obtaining of dinitrobis(aminoacidato)cobaltate(III) salts by the reaction of amino acids with the Erdmann salt or peripheral isomer of trinitrotriamminecobalt(III).     

Optical and chromaticity characteristics of the solutions of analytical forms of sulfate,formate, and acetate of chrome(III)

Conditions of formation and the absorption spectra of chrome(III) solutions, obtained by the reduction of chrome(VI) with sodium sulfite, ascorbic acid, or hydrogen peroxide, were studied. The solutions have a maximum absorption at 410–420 and 560–580 nm, and molar absorption coefficients from 17 to 80. The chromaticity functions of these forms of chrome(VI) were studied and it was shown, that they are higher in the order of 1–1.5 than molar absorption coefficients. The yellowness is maximal in all cases.     

A selective and sensitive film for electrocatalysis of ascorbic acid based on polypyrrole doped with nitroso-R(1-nitroso-2-naphthol-3,6-disulfonic acid disodium)

An electrocatalytic detection of ascorbic acid on a nitroso-R modified polypyrrole electrode has been studied. This functionalized polypyrrole film was electropolymerized by constant potential method on a platinum electrode from solution including pyrrole as monomer and nitroso-R as anionic dopant. Electrocatalytic currents of ascorbic acid were linearly dependent on its concentration in the range of 0.12–18.54 mM, with detection limit and relative standard deviation of 0.02 mM and 1.32%, respectively. This modified electrode can be used for determination of ascorbic acid in various pharmaceutical samples. Also, electrochemical behavior of this system was studied by various methods (RDE voltammetry, chronoamperometry, hydrodynamic amperometry and cyclic voltammetry).     

Extraction with long-chain amines-V Colorimetric determination of cobalt with nitroso-R salt

The colorimetric determination of cobalt with nitroso-R salt (NRS) has been modified and improved by the introduction of extraction of the Co-NRS chelate into a chloroform solution of trioctylmethylammonium chloride. Ammonium phosphate, fluoride and mainly citrate were used for masking iron, nickel, copper and calcium, which under the described conditions do not interfere even in 2000-fold excess. The method is very sensitive and permits determination of about 1 mug of cobalt per ml of the extractant.     

Oxidation of aqueous solutions of cobalt(II) in the presence of some aminoacids

Summary The complexes between cobalt(III) and aminoacids such as glutamine, asparagine, glutamic acid, aspartic acid and proline were studied.Cobalt(III)-aminoacid systems were investigated by spectrophotometry after oxidizing the cobalt(II) complexes by sodium peroxide. The variation of the absorption spectra shows the pH dependence of the process and it is clear that the formation of the complexes occurs through oxo-intermediates.Complexation ratios, molar absorptivity values and the concentration quotients at equilibrium were determined at pH 2.2 to avoid the formation of binuclear dioxygen-cobalt complexes.     

Sorption of Lanthanum, Terbium, and Erbium Complexes of Some Mono- and Bisazoderivatives of Chromotropic Acid in the Presence of Surfactants

Optimal conditions were found for the sorption of lanthanum, terbium, and erbium complexes of some derivatives of chromotropic acid: Arsenazo II, Arsenazo III, Carboxyarsenazo, and Chlorophosphonazo III on Silochrom C-120 silica gel in the presence of tetrabutylammonium bromide (TBA). Diffuse reflection coefficients and molar coefficients of the chromaticity functions of the adsorbates were determined. It was demonstrated that the preconcentration of complexes on the solid matrix in the presence of TBA increases the sensitivity of the determination of rare-earth elements by a factor of 5–50 in comparison with solutions; the use of chromaticity characteristics further increases the sensitivity by 1.5–2 orders of magnitude.     

A modified nitroso-r method for the determination of cobalt in sea water

The existing colorimetric nitroso-R method for the determination of biologically important cobalt in sea water described by Thompson and Laevastu has been studied in detail, modified and improved. A procedure is recommended in which an approximately five-fold increase in sensitivity is achieved in the measurement of the nitroso-R chelate through close control of : pH, development time of complex, conditions for decomposition of excess reagent, and employment of a wavelength of 425 mμ. The size of the water sample required for an analysis is reduced from 10 to 21. For optimum results it was found necessary for a minimum period of 7 days to elapse following precipitation with sodium carbonate prior to filtration and analysis. A previously unreported salt effect in the procedure is described which requires either construction of a calibration curve from sea water spiked with cobalt or a correction in use of standards in distilled water.A precision was obtained with a 1–2% relative standard deviation throughout range of concentrations used, with an accuracy of 3.0% at 0.5 p.p.b.     

Formation of cobalt(III) compounds with some peptides

Summary The complexes formed from cobalt(III) and dipeptides such as glycylglycine, glycylaspartic acid, glycylthreonine, glycyltyrosine and glycylproline were studied. The formation process of cobalt(III)-dipeptide species was investigated by spectrophotometry after oxidizing the cobalt(II) complexes by sodium peroxide. The formation of the cobalt(III) complexes occurs through an oxo-intermediate, as shown by the spectral behaviour, and depends on the pH of the solutions.Complex stoichiometries, molar absorptivities and concentration ratios at the equilibrium of the cobalt(III)-dipeptide complexes were determined at pH 2.2 to avoid the formation of binuclear dioxygen-cobalt complexes.     

Preparation and photochemistry of cobalt(III) amino and amino acidato complexes containing tripodal polypyridine ligands

The photochemical reactivities of cobalt(III)-diamine and cobalt(III)-amino acid compounds have been compared using complexes that also contain polypyridyl ligands. Metallacyclic complexes result from UV-induced photodecarboxylation reactions of the amino acid complexes. UV-irradiation of closely related complexes with amine donors replacing the carboxylate donors does not lead to the production of the same metallacyclic products. The reported UV-induced fragmentation of amine donors and subsequent metallacycle formation appears not to be a general reaction. Nine cobalt(III) complexes of polypyridyl ligands have been structurally characterised, including four that also contain amino acid ligands and one that contains a three-membered metallacyclic ring.     

Interaction of phenothiazines with nitroso-R salt and extractive spectrophotometric determination of phenothiazine drugs

A selective and sensitive method is based on the interaction of phenothiazines with nitroso-R salt to form 1:1 complexes which are extracted into chloroform and measured spectrophotometrically.     

Optical and chromaticity parameters of transition metal complexes with 1-nitroso-2-naphthol-3,6-disulfonic acid in the presence of surfactants

Optimal conditions for the complexation of transition metal ions [Cu(II), Ni(II), Co(II, III), and Fe(II, III)] with 1-nitroso-2-naphthol-2,6-disulfonic acid have been determined by spectrophotometry in the presence of cationic (cetylpyridinium and cetyltrimethylammonium bromides) and nonionic (OP-10, neonol) surfactants. The introduction of nonionic surfactants does not influence the optical parameters of the system, while the introduction of cationic ones leads to hyperchromic and hypsochromic (for the system Fe(III)-NRS-surfactant) effects. The stoichiometric ratios determined by the method of isomolar series and treatment of the saturation curves of cationic surfactants at pH 4.0 are Me(II): R: surfactant = 1: 2: 4, Me(III): R: surfactant = 1: 3: 6. The molar absorption coefficients and chromaticity parameters of ternary complexes have been determined. A 2–5-fold increase in the molar absorption coefficients and chromaticity functions as compared to binary systems has been revealed.     

Quantitative anodic generation of cobalt (III) at glassy carbon in acetic acid. Coulometric titrations with the generated reagent

Conditions are established for quantitative electrochemical generation of cobalt (III) at a glassy carbon working electrode in anhydrous acetic acid in the presence of potassium acetate, sodium acetate or sodium perchlorate. In anhydrous alkali-metal acetate solutions cobalt (III) is as stable as in the presence of acetic anhydride. The concentration of cobalt(III) in the solution is considerably decreased in the presence of small amounts of water. This phenomenon is much more pronounced in sodium perchlorate supporting electrolyte. Coulometric titration methods for the determination of hydroquinone, 2-methylhydroquinone and ascorbic acid with the generated oxidant have been developed. The errors of the determinations are less than ±2%.     

Optical and Chromaticity Characteristics of Ethylenediaminetetraacetates of 3d-Block Elements

Optimum conditions for the formation of mono- and mixed-ligand Cr(III), Mn(II), Fe(III), Co(II, III), Ni(II), and Cu(II) ethylenediaminetetraacetates were found. The optical and chromaticity characteristics of these complexes were determined. The prospects of using chromaticity characteristics of the studied complexes of 3d-block elements in optical methods were shown.     

Dinuclear Co(III)/Co(III) and Co(II)/Co(III) mixed-valent complexes: synthetic control of the cobalt oxidation level

The reactivity of cobalt(II) salts towards H(3)L (2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) was studied in different reaction conditions. Accordingly, the interaction of cobalt(II) acetate with H(3)L in methanol gives rise to the discrete complex [Co(III)(2)L(OAc)(2)(OMe)]*1.5H(2)O.MeOH, 1. Reaction of cobalt(II) acetylacetonate with H(3)L in the presence of dicarboxylic acids was also investigated. Thus, when cobalt(II) acetylacetonate and H(3)L are mixed with terephthalic or malonic acid in 4 : 2 : 1 molar ratios, the mixed valent [Co(II/III)(2)L(acac)(p-O(2)CC(6)H(4)CO(2)H)][Co(II/III)(2)L(acac)(OH)]*2H(2)O*2MeOH, 2 and [Co(II/III)(2)L(acac)(O(2)CCH(2)CO(2)H)][Co(II/III)(2)L(acac)(OH)]*7H(2)O, complexes are isolated. Decreasing the pH of the medium, by addition of a second mol of dicarboxylic acid, leads to [Co(II/III)(2)L(O(2)CCH(2)CO(2))(MeOH)]*2MeOH, 4, while the reaction with terephthalic acid does not proceed. 1, 2 and 4 were crystallographically characterised and all the complexes are dinuclear, with hydrogen bonds that expand the initial nodes. The magnetic characterisation, as well as the NMR spectroscopy, indicates a diamagnetic nature for 1, in agreement with the presence of Co(III), showing the aerial oxidation suffered by the cobalt(II) ions. Nevertheless, are paramagnetic. Temperature variable magnetic measurements were recorded for the crystallographically characterised complexes 2 and 4 and these studies confirm the mixed valence Co(II)/Co(III) nature of the compounds. The best fits of the magnetic data give an axial distortion parameter Delta = 628.7 cm(-1) for 2 and 698.8 cm(-1) for 4, and spin-orbit coupling constant lambda = -117.8 cm(-1) for 2 and -107.0 cm(-1) for 4. Therefore, this study shows that the oxidation degree of the initial cobalt(ii) salt by atmospheric oxygen can be controlled according to the pH of the medium.