Reaction and kinetics in system of rare earths with p-hippurochlorophosphonazo

The beta-type reactions, in which rare earth ions react with chlorophosphonazo, reagents, are extremely sensitive and have been applied widely to determination of rare earths. The reactions and kinetic behavior of the beta-type homo- and iso-nuclear chelates of rare earth with p-hippurochlorophosphonazo (CPA-pHA) have been investigated by a spectrophotometric method. Some kinetic parameters, such as the reaction rate constants, the half lives and the activation energies, were measured. The competing reactions between lanthanoid ions forming and non-forming beta-type chelates were also studied. The effects and trends of different organic solvents on the beta-type chelates have been discussed. A reaction mechanism of beta-type chelates has been proposed.     

Metal chelate exchange in the organic phase-II Extraction and exchange constants of dithizonates and diethyldithiocarbamates

Dithizonates and diethyldithiocarbamates of Ag, Tl(I), Cu(II), Zn, Cd, Hg(II), Pb, Fe(II), Co(II), Ni, Pd(II), In(III), As(III), Sb(III), Bi, Se(IV) and Te(IV) have been prepared and their reactions in carbon tetrachloride have been studied spectrophotometrically. From the exchange constants determined, the extraction constants of metal diethyldithiocarbamates have been calculated. Where formation of mixed chelates has been observed, corresponding exchange constants have been determined. Finally, the influence of organic solvents (CCl(4), CHCl(3), C(6)H(6) and C(6)H(5)Cl) on the exchange reaction of zinc diethyldithiocarbamate with dithizone has been investigated.     

Selective determination of arsenic(III) and arsenic(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of arsenic(III) and arsenic(V) with ammonium pyrrolidinedithiocarbamate, sodium diethyldithiocarbamate and dithizone in organic solvents has been investigated by means of nameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of arsenic(III) and differential determination of arsenic(III) and arsenic(V) have been developed. With ammonium pyrrolidinedithiocarbamate and methyl isobutyl ketone or nitrobenzene, when the aqueous phase/solvent volume ratio is 5 and the injection volume in the carbon tube is 20 μl, the sensitivities for 1% absorption are 0.4 and 0.5 part per milliard of arsenic, respectively. The relative standard deviations are ca. 3%. Interference by many metal ions can be prevented by masking with EDTA. The proposed methods are applied satisfactorily for determination of As(III) and As(V) in various types of water.     

Metal chelate exchange in the organic phase-III Extraction and exchange constants of dithizonates and oxinates

Reactions between dithizonates and oxinates of Ag, Tl(I), Cu(II), Zn, Cd, Hg(II), Pb, Co(II), Ni, Pd, In, Ga and Bi in chloroform have been studied spectrophotometrically. From the exchange constants determined, the extraction constants of metal dithizonates or metal oxinates have been calculated. By this method extraction constants of many metal chelates can be calculated which are difficult to determine by studies of distribution between aqueous and chloroform phases.     

Distribution of metal chelates between aqueous and surfactant phases separated from a micellar solution of a nonionic surfactant

A dilute micellar solution of poly(oxyethylene) 4-nonylphenyl ether with oxyethylene units 7.5 (PONPE-7.5) was separated into two phases (aqueous and surfactant phases) at room temperature. The partition constants of several chelating reagents and their metal chelates between the two phases were determined at 293 K and ionic strength 0.1 (NaClO₄). The partition constants of the neutral metal chelates depend on the kind of metal ions and were considerably smaller than those expected from the regular solution theory. These facts suggested that the chelates were incorporated into a hydrocarbon environment in the surfactant phase, whereas the chelating reagents were distributed in the poly(oxyethylene) part of PONPE-7.5. A brief review was also presented on the analytical applications to the extraction of metal ions and organic compounds.     

Evaluation of an ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) with ICP-AES for the determination of trace elements by solvent extraction

The introduction of volatile organic solvents and metal organic complexes into an inductively coupled plasma (ICP) is problematic due to overloading and pyrolysis effects. These include carbon built up in the torch and spectral interferences. As a consequence, solvent extraction as a method for preconcentrating trace metals for the determination by ICP has been limited. In this report a commercial ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) for the direct introduction and separation of organic solvents using ICP atomic emission spectrometry (AES) and a sequential spectrometer has been evaluated for solvent extraction of chelated trace metals. The ability of the MEMSEP to separate volatile organic flows from metal aerosols has been demonstrated by determining the recoveries of several transition metals in an oil-based methyl-isobutyl ketone (MIBK) standard relative to an aqueous solution. However, low recoveries of several metal chelates have been found evidently due to the volatilization of the organic metal species at the boiling point of MIBK (160° C). Moreover, the multielement capability and limits of detection have been limited due to sequential atomic emission detection. Advantages of the technique include enhanced limits of detection (LODs) and reduced plasma and spectral interferences.     

Evaluation of an ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) with ICP-AES for the determination of trace elements by solvent extraction

The introduction of volatile organic solvents and metal organic complexes into an inductively coupled plasma (ICP) is problematic due to overloading and pyrolysis effects. These include carbon built up in the torch and spectral interferences. As a consequence, solvent extraction as a method for preconcentrating trace metals for the determination by ICP has been limited. In this report a commercial ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) for the direct introduction and separation of organic solvents using ICP atomic emission spectrometry (AES) and a sequential spectrometer has been evaluated for solvent extraction of chelated trace metals. The ability of the MEMSEP to separate volatile organic flows from metal aerosols has been demonstrated by determining the recoveries of several transition metals in an oil-based methyl-isobutyl ketone (MIBK) standard relative to an aqueous solution. However, low recoveries of several metal chelates have been found evidently due to the volatilization of the organic metal species at the boiling point of MIBK (160° C). Moreover, the multielement capability and limits of detection have been limited due to sequential atomic emission detection. Advantages of the technique include enhanced limits of detection (LODs) and reduced plasma and spectral interferences.     

Optimization of the extraction for the determination of arsenic species in plant materials by high-performance liquid chromatography coupled with hydride generation atomic fluorescence spectrometry

A study has been conducted for the separation and the determination of arsenic species in plants using high-performance liquid chromatography–hydride generation atomic fluorescence spectrometry with emphasis on sample extraction procedures. Various extraction solvents have been applied to extract arsenic species from plants in order to investigate the uptake, transfer and accumulation processes of arsenic. The method was optimized with respect to the selection of extraction solvent, extraction time and the number of extraction steps. The analytical procedure has been validated by analyzing standard reference material GBW 82301 (peach leaves) and successfully used for the arsenic speciation in plants grown on contaminated soil near an arsenic mine. Inorganic arsenic, especially arsenate (As(V)) appears to be the major component in plants and organic arsenic species of monomethylarsenic acid and dimethylarsenic acid were detected at low concentrations.     

Enhancement effect of 3,5-dichlorophenol on the solvent extraction of copper(II) and zinc(II) with acetylacetone and trifluoroacetylacetone

The effect of 3,5-dichlorophenol (DCP) on the extraction of Cu(II) and Zn(II) with acetylacetone (Hacac) and trifluoroacetylacetone (Htfa) in heptane and carbon tetrachloride has been investigated. DCP enhances these chelate extractions; the largest effect is observed on the extraction of Cu(II) with Hacac, which is much larger than the corresponding synergistic effect seen with neutral electron donors such as trioctylphosphine oxide. By analysing the various equilibria involved, the enhanced extraction has been ascribed to the formation of association complexes of the bis(beta-diketonato) chelates (MA(2)) with DCP as MA(2).nDCP (n = 1 for A = tfa and n = 2 for A = acac) in the organic phase, and the association constants have been determined. The association constants increase in the following order of ligand and metal(II): tfa < acac and Zn(II) < Cu(II). These orders are exactly opposite those observed in the adduct formation of the chelates with neutral electron donors.     

The uranyl-chloro-substituted benzoic acid-rhodamine b-benzene extraction system

Of the chloro-substituted benzoic acids, the 2-chloro and 2,4-dichloro compounds yield higher effective molar absorptivities than benzoic acid does in the Rhodamine B-benzene extractive spectrophotometric procedure for determination of uranium(VI). Carbonyl compounds (especially acetone) in the organic phase enhance the extraction of the ion associate. The stoichiometry of the complexes has been determined, and a method of computing the extraction constants of the ion-associates developed. A spectrophotometric method for determining uranium in the presence of interfering ions has been designed.     

Micelle-mediated extraction

The extraction technique based on phase separation in aqueous micellar solutions is reviewed. The technique has now been utilized for separation and preconcentration of metal chelates, organic compounds, and proteins. Additionally, the phase behavior of the micellar solutions and recent advances in the phase separation technique are also described. In the extraction of metal chelates, distribution equilibria are considered. In contrast to conventional solvent extraction, the distribution of metal chelates into a condensed surfactant phase (surfactant-rich phase) was dependent on metal ions. Proteins were extractable into the surfactant-rich phase according to their hydrophobicity. The recent use of affinity ligands and water-soluble polymers for controlling extractability of proteins are also introduced.     

Use of Di(n-butyl) and Di(iso-butyl)dithiophosphoric Acids as Complexing Agents in the TLC Separation of Some d and f Transition Metal Ions

The thin layer chromatographic behavior of U(VI), Th(IV), lanthanides(III), Co(II), Ni(II), and Cu(II) on silica gel H with di(n-butyl) and di(iso-butyl)dithiophosphoric acids as complexing agents in the organic mobile phase has been investigated. The results obtained show that the dithiophosphate anion has a substantial effect on the migration of these metal ions. The presence of electron-donor solvents in the mobile phase increases retention, especially for U(VI), Th(IV), and lanthanides(III). The effect is explained on the basis of greater solubility of the metal chelates of the dithiophosphoric anions in the organic mobile phase, because of a solvation process. Separation was investigated for three groups of metal ions — actinides, lanthanides, and d transition metals. By choice of an appropriate organic mobile phase, separation of the pairs Th(IV)-U(VI), Pr(III)-Sm(III), Sm(III)-Gd(III), and Gd(III)-Er(III) was achieved, as was separation of Co(II), Ni(II), and Cu(II) from each other. A complex separation mechanism based on adsorption-desorption, cation exchange, and extraction is suggested.

     

Analytical application of high-molecular quaternary ammonium salts

Summary The anion-exchange extraction of a great number of mineral, organic and metal complex anions by solutions of quaternary ammonium-salts (QAS) in different solvents, including intermediate exchange with acidic dye anions, has been investigated. Extraction-photometric methods and ion-selective electrodes for the determination of organic and metal complex anions have been developed. Simple methods for synthesis and purification of QAS are described and their self-association has been investigated by electroconductivity and interphase distribution.

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Analytische Anwendung von hochmolekularen quaternären Ammoniumsalzen

     

A chemical enhancement method for the spectrophotometric determination of trace amounts of arsenic

A highly sensitive spectrophotometric method for the determination of 0.03-1.0 microg of arsenic is described. After extraction as AsI(3) into benzene, it is selectively stripped into water. Both the arsenic(III) and iodide present in the aqueous phase are made to react with iodate in acidic medium in the presence of chloride to form the anionic chloro complex, ICl(-)(2). The determination is completed after extraction of ICl(-)(2) species as an ion-pair with Rhodamine 6G into benzene and measuring the absorption of the extract at 535 nm. The coefficient of variation is 1.5% for 10 determinations of 0.5 microg of arsenic. The method has been applied to the determination of arsenic content in plant materials, high purity iron, copper base alloys and inorganic arsenic levels of natural waters.     

Structure and behavior of organic analytical reagents : Chelates of 2-(o-hydroxyphenyl)-benzoxazole, 2-(o-hydroxyphenyl)-benzothiazole and 2-(o-hydroxyphenyl)-benzothiazoline.

The reactions of the chelating reagents named in the title, with a number of metal ions, have been studied in order to evaluate the behavior of reagents containing reactive groupings analogous to those of 8-hydroxyquinoline, but so arranged as to form six-membered ring chelates with metal ions. All three reagents have been found to give less stable chelates than 8-hydroxyquinoline, indicating that for this type of reagent, six-membered ring chelates are less stable than five. 2-(o-Hydroxy-phenyl)-benzoxazole and 2-(o-hydroxyphenyl)-benzothiazole have been found to be potentially useful as organic precipitating agents for metal ions, being more selective than 8-hydroxyquinoline, which they somewhat resemble in behavior. In contrast to the oxazole and thiazole, 2-(o-hydroxyphenyl)-benzothiazoline was found to react with most of the metal ions tried. Because of the solubility of its chelates in organic solvents, 2-(o-hydroxyphenyl)-benzothiazoline may be a useful solvent extraction agent for metal ions.     

Utility of 1-octanol/octane mixed solvents for the solvent extraction of aluminum(III), gallium(III), and indium(III) with 8-quinolinol.

Using 1-octanol/octane mixed solvents, the extraction of aluminum(III), gallium(III) and indium(III) with 8-quinolinol was carried out at 25 degrees C. The formation constants of the respective metal(III) 8-quinolinolates in the aqueous phase and their partition constants between the mixed solvents and water were determined based on an analysis of the extraction equilibria. The relationship between the partition constants of 8-quinolinol and its complexes was analyzed by the regular solution theory. The molar volumes of aluminum(III), gallium(III) and indium(III) 8-quinolinolates, calculated from the present results, suggest that the electrostriction effect functions in complex forming. It has been found that octane/1-octanol mixed solvents were available not only for the extraction of metal ions, but also for determining the formation constants of these metal 8-quinolinolates in the aqueous phase and their partition constants.     

A Spectrophotometric Study of the Chelate of Iron (III) with Sorbohydroxamic Acid and Its Analytical Application

Iron (III) chelates of sorbohydroxamic acid have been studied spectrophotometrically in aqueous solution. Formation of sorbohydroxamic acid chelates was pH dependent. The “normalized absorbance” concept proposed by Likussar and Boltz has been utilized in the continuous variation plot method of determining the composition of metal chelates and the formation constants. The mole ratio of sorbohydroxamic acid to ferric ion was found to be 1 to 1 stoichiometry at pH lower than 2. The formation constant of this chelate has been evaluated to be 6.0×10¹¹ at a constant ionic strength of 0.1 M at 30°C A spectrophotometric determination of ferric ion with sorbohydroxamic acid was proposed in conjunction with the present work.     

The spectrophotometric determination of copper as the 2-furoyltrifluoroacetone chelate

The copper 2-furoyltrifluoroacetone chelate may be quantitatively precipitated from aqueous solutions and extracted into organic solvents The organic extract, which is an intense green, absorbs light strongly at a wavelength of 660 mμ. Although the β-diketone is not a specific reagent, most of the other metal chelates are colorless, not extracted, or do not absorb light at 660 μ.A rapid, sensitive, and reasonably specific spectrophotometric method for the determination of copper was developed on these properties. The method is applicable to the determination of as little as one mg of copper at concentrations as low a.s 5 p.p m. Iron, vanadium, cerium, nickel, and palladium are the only serious interferences among the more common elements. The method appears suited for the determination of copper in brass samples and in aluminum based alloys.     

Liquid extraction of molybdophosphoric and molybdoarsenic acids: application to the determination of phosphorus in the presence of arsenic

The radioisotopes phohphorus-32 and arsenic-74 have been used to study the extraction of molybdophosphoric and molybdoarsenic acids from aqueous solution with various organic solvents. A method is described for the gravivmetric determination of phosphorus in the presence of arsenic which makes use of solvent extraction with n-butyl acetate. The results obtained for the determination of phosphorus in various types of iron and steel are described.     

Differential determination of selenium(IV) and selenium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone by atomic-absorption spectrophotometry with a carbon-tube atomizer

The extraction behaviour of selenium(IV) and selenium(VI) with sodium diethyldithiocarbamate, ammonium pyrrolidinedithiocarbamate and dithizone in organic solvents has been investigated by means of flameless atomic-absorption spectrophotometry with a carbon-tube atomizer. The selective extraction of selenium(IV) and differential determination of selenium(IV) and selenium(VI) have been developed. With sodium diethyldithiocarbamate and carbon tetrachloride, when the aqueous phase/organic solvent volume ratio is 5 and the injection volume in the carbon tube is 20 microl, the sensitivity for selenium is 0.4 ng/ml for 1% absorption. The relative standard deviations are ca. 3%. Interference by many metal ions can he prevented by masking with EDTA. The proposed methods have been applied satisfactorily to determination of Se(IV) and Se(VI) in various types of water.