Selective extraction of organic compounds as ion-pairs and adducts

Selective and easily regulated systems for extraction of organic compounds as ion-pairs and/or adducts are presented. The effect of different kinds of hydrophobic agents that give adducts in the organic phase are demonstrated: mesitylene for nitrophenols, ethyl acetate and diethyl ether for hexestrol (diphenol), lipophilic alcohols for organic ammonium ion-pairs, dibenzo-18-crown-6 for ion-pairs of primary ammonium ions, HDEHP for hydrophilic aminophenols (adrenaline, isoproterenol, synephrine). It is shown that the extraction selectivity decreases with increasing content of the complexing agent in the adduct. The influence of the hydrogen-bonding character of the counter-ion and the organic solvent on the selectivity of ion-pair extractions is demonstrated with ammonium compounds (nortriptyline, amitriptyline and N-methylainitriptyline) and inorganic anions. Highly hydrophilic anionic compounds (e.g., glucuronides, cholic acid derivatives) can be extracted into chloroform as ion-pairs with large quaternary alkylammonium ions. The extraction efficiency of the cation increases with the number of methylene groups to a limit which is due to co-extraction of other sample components (e.g., buffer anions).     

Liquid—liquid distribution behavior of ion-pairs of triphenylmethane dye cations and their analytical applications

The extraction of ion-pairs of monovalent anions (chloride, bromide, iodide, perchlorate, benzenesulfonate, naphthalenesulfonate and octanesulfonate ions) with pararosaniline, crystal violet, ethyl violet and methylene blue cations is described. The extraction constants (K_ex) for these ion-pairs between an aqueous phase and several organic phases (1,2-dichloroethane, chloroform, o-dichlorobenzene, chlorobenzene, benzene and toluene) were determined. The values of log K_ex for ion-pairs with ethyl violet were on average about 2.7 times larger than those of crystal violet, which were in turn about 6 times larger than those for pararosaniline. The order of the extractability of ion-pairs was 1,2-dichloroethane > chloroform > o-dichlorobenzene > chlorobenzene > benzene > toluene, and the differences of the log K_ex between two successive solvents averaged 0.4, 1.9, 2.1, 2.6 and 0.8, respectively. Ethyl violet and crystal violet are useful extraction-spectrophotometric reagents for iodide, perchlorate and alkyl or arylsulfonate ions.     

Application of Crown Ether in Chemical Analysis Extraction of Copper(II)-Zincon Chelate Anion with Crown Ether Complex

Abstract

Crown ether-potassium ion complex extracts selectively copper-zincon anion complex as ion-pairs into chloroform phase in the presence of copper-zincon and zinc-zincon chelate anion, whereas quarternary ammonium ion extracts both anions. By measuring the absorbance of the chloroform phase at 615 nm, copper in the presence of zinc has been determined spectrophotometrically. The composition of extracted species was estimated to be Cu²⁺-zincon^4?-(KL⁺)₂.     

A new method of removing excess of reagent from organic phases in the solvent extraction of metal complex anions with quaternary ammonium salts: Spectrophotometric determination of micro amounts of cobalt with 2-nitroso-1-naphthol-4-sulfonic acid

The removal of excess reagent extracted into an organic phase in the solvent extraction of a metal complex anion with a quaternary ammonium ion is discussed. With a given chelating ligand (HO—R—SO₃H), the order of extractability is HO—R—SO₃^- > M(OR—SO₃)^n- > X^- > ^-O—R—SO₃^- when an anion such as nitrate or halide is added. If suitable amounts of the anion are added, only the excess of reagent can be removed. The principle is applied to the extraction with zephiramine of the cobalt complex anion formed with 2-nitroso-1-naphthol-4-sulfonic acid. Micro amounts of cobalt in pure nickel salts were determined spectrophotometrically.     

Ion exchange and solvent extraction of the thiourea complex cation of technetium-99 from mineral acid solutions

Sorption of macroamounts of the technetium thiourea complex cation by a cation exchange resin was studied in HNO₃ and HClO₄ solutions as a function of the concentration and reaction time for pertechnetate with thiourea. The distribution ratio reaches the value of 10³ and may be even higher (>10⁴) when sorption proceeds from a solution of the solid complex in dilute perchloric acid. The complex cation is extracted from 0.25–1M HNO₃ with solutions of the bis(1,2-dicarbollyl)cobalt(III) anion in nitrobenzene—chloroform (1:1), log D=2.75−2.95 being obtained. The preconcentration and separation of technetium on cation exchangers from dilute mineral acids would seem to be one field of application.     

Extraction of catechol violet, chrome azurol S and eriochrome cyanine R with chloroform solutions of liquid anion-exchangers

The extraction of Catechol Violet, Chrome Azurol S and Eriochrome Cyanine R with chloroform solutions of tri-n-octylamine (TOA), TOA hydrochloride and Aliquat 336 has been investigated. From the extraction isotherms, absorption spectra of the organic phases and dependence of the extraction coefficients on extractant concentration, it was found that the singly-charged anions HL(-) are extracted preferentially, but acidic groups other than sulphonate can also form ion-pairs with alkylammonium cations at higher pH values of the aqueous phase, and at high acidity these dyes can be extracted other than by an anion-exchange reaction. The three dyes (especially Eriochrome Cyanine R and Chrome Azurol S) were strongly extracted with the liquid anion-exchanger used and Aliquat 336 was a better extractant than TOA or TOA hydrochloride. The absorption spectra for the organic phases containing Chrome Azurol S and Eriochrome Cyanine R depended on the extractant used.     

2-[2-(5-Bromopyridyl)azo]-5-dimethylaminophenol; a new sensitive reagent for cadmium

Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beer's law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·10⁵ 1 mol^?1 cm^?1 at 555 nm.     

Studies on mixed ligand complexes of samarium(III), europium(III) and dysprosium(III) with 1-nitroso-2-naphthol and trioctylphosphine oxide

The extraction behavior of Sm(III), Eu(III) and Dy(III) with 1-nitroso-2-naphthol (HA) and trioctylphosphine oxide (TOPO) in methyl isobutyl ketone (MIBK) from aqueous NaClO₄ solutions in the pH range 4–9 at 0.1M ionic strength has been studied. The equilibrium concentrations of Sm and Dy were measured using their short-lived neutron activation products,¹⁵⁵Sm and^165mDy, respectively. In the case of Eu, the concentrations were assayed through the^152,154Eu radiotracer. The distribution ratios of these elements were determined as a function of pH, 1-nitroso-2-naphthol and TOPO concentrations. The extractions of Sm, Eu and Dy were found to be quantitative with MIBK solutions in the pH range 5.9–7.5, 5.6–7.5 and 5.8–7.5, respectively. Quantitative extraction of Eu was also obtained between pH 5.8 and 8.8 with chloroform solutions. The results show that these lanthanides (Ln) are extracted as LnA₃ chelates with 1-nitroso-2-naphthol alone, and in the presence of TOPO as LnA₃(TOPO) and LnA₃(TOPO)₂ adducts. The extraction constants and the adduct formation constants of these complexes have been calculated.     

Energetics of guest binding to calix[4]arene molecular containers

The synthesis of calix[4]arene-based molecular containers 1 and 2 along with the thermodynamic behaviors of cation binding are reported. The containers encapsulated N-methylpicolinium salts to form 1:1 host-guest complexes in chloroform. The thermodynamic investigations of the containers provide contrastive pictures for the process of their guest encapsulations. The encapsulation of 1 with the N-methylpicolinium cations, bearing a series of counter anions, was primarily enthalpy-driven. The enthalpic difference among the host-guest complexes of the salts was directly related to the total electrostatic stability of the ion-pairs. When 2 encapsulated a series of the N-methylpicolinium cations within its cavity, negative heat capacity changes were observed. This suggests that the changes in the solvation spheres of the container and its guest before and after the formation of the host-guest complex depend on temperature.     

Effect of cobalt(III) 1-nitroso-2-naphtholate on free-radical polymerization to vinyl monomers

It has been shown that, at 70°C, cobalt(III) 1-nitroso-2-naphtholate inhibits the free-radical polymerization of styrene, methyl methacrylate, butyl methacrylate, and butyl acrylate. The induction period linearly increases with complex concentration. The polymerization of styrene (120°C) carried out in the presence of cobalt(III) 1-nitroso-2-naphtholate shows typical features of pseudoliving polymerization, namely, linear ln[M]₀/[M]-time and molecular mass-conversion plots. When the monomers are allowed to stand with a complex (7 × 10^?3 mol/l) and an initiator (5 × 10^?3 mol/l) for 1 day at 20°C, the ESR signal corresponding to the nitroxide radical appears. In the course of polymerization, the signal disappears, indicating the consecutive transformation of the cobalt(III) 1-nitroso-2-naphtholate radical into the macronitroxide adduct. Polystyrene samples isolated at various conversions initiate the secondary polymerization of styrene and its block copolymerization with methyl methacrylate.     

Extraction of small amounts of dialkylphosphorodithioates with tetraphenylarsonium

The extraction behaviour of ion-pairs formed by dialkylphosphorodithioates with tetraphenylarsonium cation was examined for the dichloromethane—water system. The mole ratio method, with spectrophotometric and conductimetric measurements of the organic phase, showed the mole ratio of the ion-pair to be 1:1. Dissociation of the ion-pairs occurred at concentrations in the aqueous phase lower than 10^?1 mol dm^?3 for the dimethyl compound and 6 × 10^?4 mol dm^?3 for the diethyl analogue. Under favourable experimental conditions, dialkylphosphorodithioates can be collected from aqueous solutions at concentrations not exceeding 1 μg cm^?3 (ca. 5 × 10^?6 mol dm^?3), with extraction efficiencies of 86–95%. Dialkylphosphorothioates are extracted much less efficiently; diethylphosphate and inorganic phosphate are not extracted.     

Structural insights into the extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid and 2-ethylhexyl 4-pyridinecarboxylate ester

Abstract

In this work, to elucidate the synergistic extraction mechanism of cobalt(II) with dinonylnaphthalene sulfonic acid (HDNNS) and 2-ethylhexyl 4-pyridinecarboxylate ester (L), hexaaquacobalt(II) naphthalene-2-sulfonate (compound 1) was prepared using naphthalene-2-sulfonic acid (HNS, the short chain analog of HDNNS) and di-methyl isonicotinate tetraaquacobalt(II) naphthalene-2-sulfonate (compound 2) was prepared using methyl isonicotinate (L^I, a short chain analog of 2-ethylhexyl 4-pyridinecarboxylate ester) and HNS; the compounds were studied by single crystal X-ray diffraction. Moreover, 2 and the actual extracted cobalt(II) complex were further investigated by Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The results indicated that the actual extracted cobalt(II) complex possesses a similar coordination structure as 2. Combined with the results obtained by single crystal X-ray diffraction of 1 and 2, FT-IR and ESI-MS of 2 and the actual extracted cobalt(II) complex, it is reasonable to conclude that the extracted cobalt(II) complex with the actual synergistic mixture is much more stable than the cobalt(II) complex with HDNNS alone. Therefore, the extraction selectivity cobalt(II) is effectively enhanced with the addition of 2-ethylhexyl 4-pyridinecarboxylate ester to HDNNS.     

Environmental Status of Cobalt and Its Microdetermination With 7-Nitroso-8-Hydroxyquinoline-5-Sulfonic Acid In Waters,Aquatic Weeds and Animal Tissues

Abstract

A method is presented for the spectrophotometric microdetermination of cobalt (II) in fresh waters, aquatic weeds, and animal tissues employing 7-nitroso-8-hydroxyquinoline-5-sulfonic acid. the method enables direct determination of cobalt (II) in presence of a large number of anions and cations commonly associated with cobalt, and is adequate for determining the metal in the concentration range of 0.001–10 ppm, which is commonly encountered in environmental samples.     

Complexation and extraction behavior of trivalent indium with multiple proton ionizable p�Ct-butylcalix[5]arene pentacaarboxylic acid derivative: a new efficient solvent extraction reagent for indium

Complexation behavior of plural ion-exchangeable p?Ct-butylcalix[5]arene pentacarboxylic acid derivative towards trivalent indium has been investigated along with its monomeric analog from weakly acidic media into chloroform. The cyclic structure of calixarene ligand providing certain cavity and cooperativity of functional groups significantly affect the complexation behavior and calixarene derivative is an excellent extractant over monomeric analog. The extraction mechanism is ion exchange and carboxylic acid groups are adequate functional sites for extraction. Mononuclear and/or polynuclear species of indium and monomeric or bridged dimeric species of calixarene are involved in complexation and the composition of extracted complex varied with solution pH. One mole of calix[5]arene derivative tend to extract 3.5 mol of indium. The loaded indium was quantitatively back extracted with 1 mol dm^?3 hydrochloric acid solution.     

Sorption of cobalt on modified clinoptilolites

A method of radioactivation analysis has been developed for the substoichiometric determination of cobalt, copper and manganese in glass and glass-making materials. The substoichiometric extraction of cobalt with α-nitroso-β-naphthol was studied and simple procedures are suggested for the determination of the three elements. Cobalt is extracted substoichiometrically as α-nitroso-β-naphtholate into chloroform from solution of pH 6.2, copper as dithizonate in carbon tetrachloride from weak acidic solution, and manganese as tetraphenylarsonium permanganate into chloroform after oxidation to permanganate. Contents from 2 ppm to 3 ppb of cobalt, copper and managanese were analysed in glass-making materials, and it is shown that the method for their determination is reliable and superior in accuracy and reproducibility.     

A study on the solvent extraction of Se/IV/ with 2-mercaptobenzothiazole into chloroform

The extraction of Se/IV/ from hydrochloric acid medium with 2-mercaptobenzothiazole/2-HMBT/into chloroform has been studied. The effect of various parameters on the extraction coefficient value such as molarity of hydrochloric acid, time of equilibration, effect of cations and anions etc., has been evaluated. The stoichiometry of the extracted species was determined by the method of substoichiometric extraction and slope ratio method and was found to be 1∶4. Decontamination factors for many elements in the substoichiometric extraction of Se/IV/ was also obtained.     

Selection of the counter-cation in the solvent extraction of anionic chelates: Spectrophotometric determination of trace amounts of cobalt with 2-nitroso-1-naphthol-4-sulphonic acid and tetrabutylammonium ion

The importance of selecting the most suitable counter-cation in the solvent extraction-spectrophotometric determination of an anionic metal chelate containing a sulphonic acid group is demonstrated and discussed. In the case of cobalt and 2-nitroso-1-naphthol-4-sulphonic acid (nitroso-NW acid), the most suitable counter-cation is the tetrabutylammonium ion (Bu(4)N(+)): in this case only the ion-pair of the anionic cobalt chelate is extracted into chloroform and the excess of the nitroso-NW acid remains in the aqueous phase. The absorption maximum of the chelate in chloroform is at 307nm, at which the molar absorptivity is 6.5 x 10(4)l.mole(-1).cm(-1). The absorbance of the reagent blank at 307 nm is less than 0.010. By use of nitroso-NW acid and Bu(4)N(+), trace amounts of cobalt may be determined in nickel salts and in iron and steel samples.     

Electrothermal atomic absorption spectrometric determination of cobalt in steel after chloroform extraction of its 1-nitroso-2-naphthol complex

Direct determination of μg g^-1 levels of cobalt in steels and corrosion products by electrothermal atomic absorption is difficult because of suppression of the cobalt signal by mineral acids and other metals. Extraction or cobalt with 1-nitroso-2-naphthol into chloroform in the presence of citrate overcomes this problem. Samples (0.4–10 mg) may be dissolved in a variety of acids, and a detection limit of 0.005 μg g^-1 in the chloroform extract is obtained.     

Extraction of cobalt(II) with 7-(1-decenyl)-8-quinolinol into chloroform

Extraction of cobalt(II) with 7-(1-decenyl)-8-quinolinol (HRql) into chloroform was examined. The best cobalt extraction occurs in the pH region 5.5–9. In this region several other cations are extracted. The values of K_ex and pH_0.5 for cobalt extraction were found to be ?8.6 and 3.19 respectively. The composition of the extracted complex was found to be Co(Rql)₃. Cobalt is poorly reextracted from Co-HRql complex into the aqueous phase, the best results were obtained using HCl as a stripping agent.     

Atomic Absorption Spectrometric and Spectrophotometric Trace Analysis of Indium in Environmental Samples

Abstract

Indium (III) was selectively extracted at pH 5.2–5.9 with N-p-methoxyphenyl-2-furylacrylohydroxamic acid (MFHA) into chloroform. BPAR [5-bromo-4(2-pyridylazo) resorcinal] was added to the extract to form an intensely red coloured ternary complex measurable spectrophotometrically at 515 nm (? = 5.81 × 10⁴ 1 mol^?1 cm^?1). The extraction system enabled enrichment of indium and determination of the metal down to 10^?4 ppm (0.1 ppb) levels. For atomic absorption spectrometric determination, indium was extracted with MFHA into methyl isobuyl ketone and measured at 303.9 nm resonance line in the air-acetylene flame. Both the methods were