Preparation and analytical properties of a chelating resin functionalized with 1-hydrazinophthalazine ligand

A poly[styrene-co-(divinylbenzene)] resin (XAD-4) functionalized with 1-hydrazinophthalazine ligand has been prepared and its analytical properties investigated. The pH dependence of sorption of metal ion on the resin has been determined for Cu(II), Ni(II), Co(II), Zn(II), Cd(II), Pb(II), Fe(III) and Cr(III). Trace amounts of these metal ions were quantitatively retained on the resin and recovered by eluting with 1 mol l(-1) hydrochloric acid. The resin was found to be selective for Fe(III) and its separation from other metal ions was carried out effectively. Metal ions concentrations were determined using AAS.     

Extraction and complexing of copper(II) with benzoic acid N,N-dihexylhydrazide

The solubility and acid-base properties of benzoic acid N,N-dihexylhydrazide (BDHH) were studied. The extraction of copper(II), cobalt(II), nickel(II), zinc(II), iron(III), platinum(II), platinum(IV), chromium(III), chromium(VI), palladium(II), and molybdenum(VI) with this reagent was studied. It was shown that BDHH most efficiently extracts copper(II) from ammonia solutions and chromium(VI) from sulfuric acid solutions. In the extraction of copper(II), complexes with the [Cu(II)]: [BDHH] = 1: 1 and 1: 2 stoichiometries were found to form. The structure of the 1: 2 complex was suggested proceeding from its IR spectra. A copper(II) extraction isotherm was plotted.     

Preparation and Analytical Application of a New Chelating Ion Exchange Resin Containing Thioglycolic Acid

Starting from copolymerization of acrylonitrile and divinylbenzene by emulsion polymerization technique, a macroporous, crosslinked polyacrylonitrile copolymer was synthesized. The nitrile groups on the copolymer resin were converted into carboxylic acid groups by hydrolysis with strong alkaline solution of sodium hydroxide to obtain the resin matrix with carboxylic acid groups. A new chelating ion exchange resin containing alkylthioglycolate was prepared by esterification of carboxylic acid groups on the resin matrix and thioglycolic acid with 1,6-hexanediol as binding part. After studies of the basic characters, ion exchange ability, exchange rate and acidity of the medium, it was found that the new resin obtaind was highly selective for silver(I), mercury(II), gold(III) and bismuth(III) in acidic-aqueous solution. Separation of these metal ions from each other and concentration of these metal ions from very dilute solution were studied by liquid chromatography using a short column of this new resin. The analytical applications of this new resin are reported.     

Speciation studies by capillary electrophoresis- Simultaneous determination of chromium(III) and chromium(VI)

A method for the simultaneous determination of chromium(III) and chromium(VI) by capillary electrophoresis (CE) has been developed. The chromium(III) has been chelated with 1,2-cyclohexanediaminetetraacetic acid (CDTA) in order to impart a negative charge and similar mobility to both the chromium(III) and the chromium(VI) species. The effects of the amount of the reagent, pH and heating time required to complete the complexation have been studied. Factors affecting the CE behaviour such as the polarity of electrodes and the pH of electrophoretic buffer have been investigated. The separated species have been monitored by direct UV measurements at 214 nm. The detection limits achieved are 10 g/l for Cr(VI) and 5 g/l for Cr(III) and linear detector response is observed up to 100 mg/l. The procedure has been applied to the determination of both chromium species in industrial electroplating samples and its accuracy was checked by comparing the results (as total chromium) with those of atomic absorption spectrometry. No interference occurred from transition metal impurities under optimized separation conditions. The method is also shown to be feasible for determining Cr(III) as well as other metal ions capable to form complexes with CDTA (like iron(III), copper(II), zinc(II) and manganese(II)) in pharmaceutical preparations of essential trace elements.     

Preparation and properties of a chelating resin containing the nitrosoresorcinol group

A macroreticular polystyrene-based chelating resin with the nitrosoresorcinol group as the functional group has been synthesized. The resin shows selectivity for copper(II), iron(III), and cobalt(II). The sorption behaviour of cobalt(II) is examined in detail, with the intention of using the resin analytically. Iron(III) and cobalt(II) are separated in a column operation by stepwise elution with oxalic acid solution and hydrochloric acid respectively.     

Determination of microamounts of iron by hydroxamate resin colorimetry

Summary A new, sensitive chelating ion-exchanger colorimetric method has been developed for the determination of iron at the g/l level in water, based on the direct measurement of light absorption of iron hydroxamate resin complex. In 0.2 N perchloric acid solution, iron could be rapidly, selectively and quantitatively absorbed on the hydroxamate resin. The calibration curve for iron(III) of a 25 ml solution was linear in the concentration range 8.00×10^–6 to 5.00×10^–5 M. For iron(III) with larger sample volumes, the relative detection limit was increased. Most of the metals interfered negligibly, such as Ca(II), Co(II), Cu(II), Ni(II) and Zn(II), except for higher concentration of lead(II) and mercury(II) when present at up to 400 times the concentration of iron(III). The effects of EDTA, glycine, thiourea, phosphate, nitrate and chloride on the retention of iron(III) were also examined. Only thiourea significantly influenced the retention of iron(III). The presence of sodium chloride even at a concentration of 3.5×10⁴ times that of iron(III) did not interfere at all.

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Bestimmung von Mikromengen Eisen durch Hydroxamatharz-Colorimetrie

     

1,3-pyrimidinyl(2,4,6-pyrimidine trione) and its metal chelates

Summary A new tetradentate ligand 1,3-pyrimidinyl(2,4,6-pyrimidine trione) and its chromium(III), manganese(II), iron(III), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes have been prepared and characterized by elemental analysis, magnetic susceptibility measurements, and electronic and i.r. spectra. Conductivity measurements show the complexes to be non-electrolytes. An octahedral geometry for trivalent ions [iron(III) and chromium(III)] has been proposed, whereas all divalent metal ions, except for copper(II), appear to be tetrahedral. The 10 Dq values suggest that the ligand is as strong as ethylenediamine. The values indicate a considerable orbital overlap in the metal-ligand bond.     

Redox titrations at millimolar concentration in n,n-dimethylformamide media

Potentiometric oxidation-reduction titrations in N,N-dimethylformamide (DMF) have been shown to be valid at millimolar concentrations of titrand. Forward and reverse titrations that involve the oxidants copper(II), chromium(VI), iron(III), and mercury(II) with the reductants titanium(III), cobalt(II), ascorbic acid, cysteine, and thiolactic acid have been examined. Some preliminary results of titanium(III) in DMF titrimetry in the determination of copper and iron in alloys are presented.     

Vanadium(III) as an analytical reagent: The titrimetric determination of iron, copper, thallium, molybdenum, uranium, vanadium, chromium and manganese

Vanadium(III) solutions can be used in direct titrations of iron(III), copper(II), thallium(III), molybdenum(VI), uranium(VI), vanadium(V), chromium(VI) and manganese(VII) in milligram amounts. The titrations are done at 70-80 degrees for iron(III), copper(II), thallium(III), molybdenum(VI) and at room temperature for vanadium(V), chromium(VI) and manganese(VII). Uranium(VI) is titrated at 70-80 degrees in presence of iron(II). The vanadium(III) solution is prepared by reduction of vanadium(V) to vanadium(IV) with sulphur dioxide, followed by addition of phosphoric acid and reduction with iodide, and is reasonably stable.     

Simultaneous flow injection determination of iron(III) and vanadium(V) and of iron(III) and chromium(VI) based on redox reactions

A flow injection analysis (FIA) method is presented for the simultaneous determinations of iron(III)-vanadium(V) and of iron(III)-chromium(VI) using a single spectrophotometric detector. In the presence of 1,10-phenanthroline (phen), iron(III) is easily reduced by vanadium(IV) to iron(II), followed by the formation of a red iron(II)-phen complex (lambda(max) = 510 nm), which shows a positive FIA peak at 510 nm corresponding to the concentration of iron(III). On the other hand, in the presence of diphosphate the reductions of vanadium(V) and/or chromium(VI) with iron(II) occur easily because the presence of diphosphate causes an increase in the reducing power of iron(II). In this case iron(II) is consumed during the reaction and a negative FIA peak at 510 nm corresponding to the concentration of vanadium(V) and/or chromium(VI) is obtained. The proposed method makes it possible to obtain both positive (for iron(III)) and negative (for vanadium(V) or chromium(VI)) FIA peaks with a single injection.     

n-arylhydroxamic acids as reagents for vanadium(v) : Spectrophotometric determination of vanadium(v) with n-m-tolyl-p-methoxybenzohydroxamic acid

A study of the coloured complexes of 51 N-arylhydroxamic acids with vanadium(V) in hydrochloric acid media is described. The absorption spectra of the coloured chloroform extracts and the molar absorptivities are compared. The effects of different substituents attached to the carbon and nitrogen atom of the hydroxamic acid functional group are discussed. A rapid extraction-spectrophotometric method for the determination of vanadium(V) is described, employing the most promising of these reagents, N-m-tolyl-p-methoxybenzohydroxamic acid. The method is highly selective and tolerates large amounts of diverse ions usually associated with vanadium-bearing materials including iron(III), aluminium(III), chromium(III), nickel(II), cobalt(II), zinc(II) and manganese(II).     

Adsorption of chloro-complexes of the first row transition elements by Dowex A-1

A study has been made of the adsorption of chlorocomplexes of the first row transition metals by the chelating resin Dowex A-1, and possible mechanisms for adsorption have been reviewed. Relative adsorption follows the series Zn(II) > Co(II) = Fe(III) Cu(II) > Mn(II). Negligible adsorption occurred with Cr(III) and none with V(IV) and Ni(II). Maximum adsorption of Zn(II) occurred from 3M hydrochloric acid and for the other metals from 8M acid.     

Development of a voltammetric method for the determination of iron(III) in Zn-Fe alloy galvanic baths

A square wave voltammetric method with a static mercury drop electrode (SMDE) was developed for the quantitative determination of iron (III) in Zn-Fe alloy galvanic baths. Real alloy bath samples were analyzed by the standard addition method and recovery tests were carried out. 0.50 mol L-1 sodium citrate (pH 6.0) or 0.20 mol L-1 oxalic acid (pH 4.0) were applied as supporting electrolytes resulting in both cases in a peak potential of about -0.20 V vs. AgIAgCl (saturated KCl). The iron (III) concentration in the alloy bath was 9.0 x 10(-4) mol L-1. A good correlation (r = 0.9999) was achieved between the iron (III) concentration and the peak current in the electrolytes studied, with linear response ranges from 1.0 x 10(-6) to 1.2 x 10(-4) mol L-1. Interference levels for some metals such as copper (II), lead (II), chromium (III) and manganese (II) that can hinder the Zn-Fe alloy deposition were evaluated; only copper (II) interferes seriously.     

Preconcentration and spectrophotometric determination of chromium(vi) in natural waters by coprecipitation with barium sulfate

A selective preconcentration of chromium(VI) is proposed for analysis of natural waters. Chromium(VI) is quantitatively separated from chromium(III) by coprecipitation with barium sulfate; salicylic acid is used as a masking agent for iron(III), aluminum(III) and chromium(III). The precipitate is fused with alkali carbonate, and the chromium(VI) in the melt is isolated with hot water and determined spectrophotometrically with diphenylcarbazide. The detection limit is 0.02 μg l^-1 the relative standard deviation for chromium(VI) in river water is less than 5%.     

Selective separations by reactive ion exchange: Part II. preconcentration and determination of complex iron cyanides in waters

Reactive ion exchange has been applied to the determination of p.p.b. concentrations of hexacyanoferrate(II) and hexacyanoferrate(III) in various water matrices. The in situ precipitation of copper hexacyanoferrate(II) or hexacyanoferrate(III) preconcentrates the complex cyanides on shallow beds of sulfonated cation-exchange resin in the copper(II) form. Hydrochloric acid reactively elutes other cations including concomitant iron species from the resin bed and, finally, aqueous ammonia reactively releases and elutes the hexacyanoferrate(II) (or III) species through the formation of the copper-ammine complex. Preconcentration factors of 100 or more are possible when 1-1 samples are used. Final determination of the complex cyanides is performed by atomic absorption spectrometry (for iron).     

Improved separation of iron from copper and other elements by anion-exchange chromatography on a 4% cross-linked resin with high concentrations of hydrochloric acid

Iron(III) can be separated from copper(II) and many other elements by eluting these from a column of AG1-X4 anion-exchange resin with 8M hydrochloric acid, while iron(III) is retained and can be eluted with 0.1M hydrochloric acid. The separation is much better than the customary one with 3.5M hydrochloric acid. Columns containing only 8.8 ml (3 g) of resin can separate traces or up to more than 1 mmole of iron(III) from more than 1 g of copper. Mn(II), Ni, Al, Mg and Ca are quantitatively eluted together with copper(II). Lead, the alkali metals, Be, Sr, Ba, Ra, Sc, Y and the lanthanides, Ti(IV), Zr, Hf, Th and Cr(III) have not been investigated in detail but should be separated according to their known distribution coefficients. Separations are sharp and quantitative, less than 1 mug of copper remaining in the iron fraction when more than 1 g was present originally. Relevant elution curves and results of the quantitative analysis of synthetic mixtures are presented.     

Speciation studies by capillary electrophoresis- Simultaneous determination of chromium(III) and chromium(VI)

A method for the simultaneous determination of chromium(III) and chromium(VI) by capillary electrophoresis (CE) has been developed. The chromium(III) has been chelated with 1,2-cyclohexanediaminetetraacetic acid (CDTA) in order to impart a negative charge and similar mobility to both the chromium(III) and the chromium(VI) species. The effects of the amount of the reagent, pH and heating time required to complete the complexation have been studied. Factors affecting the CE behaviour such as the polarity of electrodes and the pH of electrophoretic buffer have been investigated. The separated species have been monitored by direct UV measurements at 214 nm. The detection limits achieved are 10 microg/l for Cr(VI) and 5 microg/l for Cr(III) and linear detector response is observed up to 100 mg/l. The procedure has been applied to the determination of both chromium species in industrial electroplating samples and its accuracy was checked by comparing the results (as total chromium) with those of atomic absorption spectrometry. No interference occurred from transition metal impurities under optimized separation conditions. The method is also shown to be feasible for determining Cr(III) as well as other metal ions capable to form complexes with CDTA (like iron(III), copper(II), zinc(II) and manganese(II)) in pharmaceutical preparations of essential trace elements.     

Solvation of iron and chromium complexes in alcohol–water mixtures

Solubilities are reported for the perchlorates of five iron(II)-diimine complexes in t-BuOH–H₂O and one in MeOH–H₂O mixtures, for three iron(III)-3-hydroxy-4-pyranonate and three iron(III)-3-hydroxy-4-pyridinonate complexes in MeOH–H₂O and t-BuOH–H₂O, and for two chromium(III)-3-hydroxy-4-pyranonate complexes in MeOH–H₂O. Transfer chemical potentials are thence derived for the various iron(II), iron(III) and chromium(III) complexes, for transfer from H₂O into the respective mixed solvents (at 298.2 K). These results are combined with values reported earlier for related complexes, and for other alcohol–H₂O mixtures, to give an overall picture of solvation, expressed in the thermodynamic format of transfer chemical potentials, for iron(II)-diimine, iron(III)-3-hydroxy-4-pyridinonate and chromium(III)-3-hydroxy-4-pyranonate complexes in H₂O-rich aqueous-alcohol mixtures. Some spectroscopic (¹H-n.m.r.; i.r.) and kinetic (aquation rate constants at 298.2 K) data are reported for the chromium(III) complexes.     

Kinetics and mechanism of oxidation of the chromium(III)-dl-valine complex/periodate reaction. Evidence for iron(II) catalysis

Oxidation of the chromium(III)-dl-valine complex [CrIII(L)2(H2O)2]+ by periodate has been investigated in aqueous medium. The kinetics of the reaction in aqueous medium in the presence of iron(II) as catalyst obeyed the rate law:Catalysis by iron(II) is believed to be due to the oxidation of iron(II) to iron(III), which acts as the oxidizing agent. The thermodynamic activation parameters were calculated and we propose that electron transfer proceeds through an inner-sphere mechanism via coordination of IO4– to chromium(III).     

Quantitative separation of gallium from zinc, copper, indium, iron(III) and other elements by cation-exchange chromatography in hydrobromic acid-acetone medium

Gallium can be separated from Zn, Cu(II), In, Cd, Pb(II), Bi(III), Au(III), Pt(IV), Pd(II), Tl(III), Sn(IV) and Fe(III) by elution of these elements with 0.50M hydrobromic acid in 80% acetone medium, from a column of AG50W-X4 cation-exchange resin. Gallium is retained and can be eluted with 3M hydrochloric acid. Separations are sharp and quantitative except for iron(III) which shows extensive tailing. With 0.20M hydrobromic acid in 80% acetone as eluting agent, all the species above except iron(III) and copper(II) can be separated from gallium with very large separation factors. Only a 1-g resin column and small elution volumes are required to separate trace amounts and up to 0.5 mmole of gallium from more than 1 g of zinc or the other elements. Hg(II), Rh(III), Ir(IV), Se(IV), Ge(IV), As(III) and Sb(III) have not been investigated, but should be separated together with zinc according to their known distribution coefficients. Relevant elution curves, results for the analysis of synthetic mixtures and for amounts of some elements remaining in the gallium fraction are presented.