Extraction of technetium by crown ethers and cryptands

Extraction of technetium with dibenzo-18-crown-6 was studied from alkline media. Effects of crown cavity size, substitutions, organic solvents and type of base on the distribution coefficient were discussed. High separation factors of technetium from other elements in an irradiated uranium sample were attained.     

Synergistic extraction of americium(III) with 2-thenoyltrifluoroacetone and crown ethers

Extracton, of Am³⁺ in benzene with 2-thenoyltrifluoroacetone (HTTA) and crown ethers (CEs) such as 15-crown-5, 18-crown-6, dicyclohexano-18-crown-6, dibenzo-18-crown-6, dicyclohexano-24-crown-8, and dibenzo-24-crown-8 was investigated. Synergistic effect by CE was observed regardless of the kind of CE examined. The extracted species was found to be Am(TTA)₃(CE), and adduct formation constants between Am(TTA)₃ and CE in the organic phase were determined. The sequence of constant could not be explained only by basicity of CE and the steric effect of CE should be taken into account to elucidate the adduct complex formation.     

Extraction of technetium from ascorbic acid medium with crown ethers

The extraction of technetium from ascorbic acid medium with dibenzene-18-crown-6 /DB-18C6/ and 18-crown-6 /18C6/ dissolved in benzene and nitrobenzene was studied. The effect of crown ether substition, concentration of the extracting agent as well as the pH of the aqueous solution on the distribution coefficient was investigated. Nitrobenzene was found to be a rather promising diluent.     

Comparative photophysical behaviour of naphthalene-linked crown ethers and aza crown ethers of varying cavity dimensions

A comparative time-resolved emission studies of several naphtho-crown ethers I–V, where metal ions can be complexed in a predetermined orientation with respect to the naphthalene (Naph) π-plane and naphthalene-linked aza crown ethers (L1 and L2) have been presented. In both the systems, crown ethers and aza crown ethers, naphthalene fluorescence gets quenched. In the systems I to V, the quenching is mainly due to efficient spin-orbit coupling (SOC) leading to greater population of the lowest triplet state of naphthalene. This SOC depends on the orientation of the crown ring with respect to the Naph-π-plane. However, in the systems L1 and L2, the quenching is due to photoinduced electron transfer (PET) from nitrogen lone pair of the aza crown ring to naphthalene moiety and consequent exciplex formation. The results have been interpreted using the time-resolved emission studies of all the compounds in various solvents, their alkali metal ion complexes, and protonated ligands.     

Extraction of technetium from aqueous medium with the aid of crown ethers dissolved in benzene-acetone mixture

The extraction of technetium from ascorbic acid medium by dibenzene-18-crown-6 /DB18C6/ dissolved in benzene mixed with acetone in different ratios was studied. Benzene mixed with acetone in 12 ratio proved to be the best composition of the diluent. The extracted species have the general formula TcO₂.nH₂O.xCE.yCH₃COCH₃.     

On the separation of molybdenum and technetium crown ether as extraction agent

Separation of⁹⁹Mo and^99mTc can be performed with high selectivity using the crown ether 2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-2,11-diene /DB18C6/ diluted with nitrobenzene. The high efficiency is attributed to the rather low extractability of molybdenum as compared with that of technetium.     

Synergistic solvent extraction of Co(III) by thenoyltrifluoroacetone and some organophosphorus compounds

The extraction of Co(III) from aceticacid-acetate buffer solutions with various mixtures of ligands has been studied. Thenoyltrifluoroacetone mixed with triphenylphosphine oxide, trioctylphosphine oxide or tributyl phosphate were used as extractants. The effect of different parameters affecting the distribution ratio was studied in detail. Also, the corresponding thermodynamic parameters are calculated and discussed, together with the structures of extracted species.     

Selective lithium ion extraction with chromogenic monoaza crown ethers

Two chromogenic monoaza crown ethers were synthesized and investigated for their lithium extraction capabilities. The chromogenic monoaza 14-crown-4 compound exhibited the best selectivity for lithium over sodium; ca. 2800, with a detection limit of 0.08 ppm.     

Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC

Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na⁺] and not on [K⁺] at concentrations of K⁺ from 5×10^–7 to 10^–1 mol l^–1. Hence, actinomycin D may be classified as an ionophore-antibiotic.     

Complex forming and extraction properties of oligo benzo-fused crown ethers

The complex forming properties with alkali metal and ammonium ions of a series of oligo benzo-condensed 18-crown-6 ethers1–8 having a different gradation of lipophilicity and of molecular rigidity are investigated by voltammetry at the interface of two immiscible electrolyte solutions (ITIES) and by a liquid-liquid extraction technique. The experimental results obtained in the two phase system H₂O/nitrobenzene are discussed in relation to the structure of the crown and the cation type. The stability constants for the 1 : 1 complexes of Na⁺, K⁺, Rb⁺, Cs⁺ and NH ₄ ⁺ in nitrobenzene have been determined and compared with the extraction constants for the 1: 1 complexes of Na⁺ and K⁺ and for the 1 : 1 and 1 : 2 complexes of Cs⁺, showing the effect of oligo benzo condensation for the 18-crown-6 system.     

Synergistic solvent extraction of cerium(III) with mixtures of thenoyltrifluoroacetone and dialkyl sulfoxides

Synergism in the extraction of Ce(III) from thiocyanate solutions has been investigated using mixtures of 2-thenoyltrifluoroacetone (HTTA) and bis-2-ethylhexyl sulfoxide (B2EHSO) or di-n-octyl sulfoxide (DOSO) in benzene. A very high synergistic enhancement of the order of 10⁵ has been observed. If a mixture of both dialkyl sulfoxides (B2EHSO+DOSO) is used, an additional synergistic effect is found due to the formation of a mixed, solvated complex when both reagents are added to the metal chelate. These extraction data have been analyzed theoretically with the aid of a computer by taking into account complexation of the metal in the aqueous phase by inorganic ligands and plausible complexation in the organic phase. The equilibrium constants of the various product species have been deduced by non-linear regression analysis.     

Calculation of lithium isotope effects in extraction systems with crown ethers

Complexes of lithium salts with benzo-15-crown-5 and its derivatives have been prepared. Their structure has been established by X-ray diffraction analysis. On the basis of obtained data, the dependence of partition function ratios for isotopic forms (β factors) of these compounds on the type of extracted salt anion and other factors has been analyzed. Taking into account previously calculated value of β factor for aqua complex of lithium ion, single isotope extraction separation factors (α) for Li⁶–Li⁷ pair have been determined. Quantum chemical calculations for vibrational frequencies of isotope forms of complexes with crown ethers have been performed with the aid of Firefly (PC GAMESS) software. Lithium cation complexes with crown ethers have been calculated using RHF/6-311++G** basis set. Isotope extraction separation factors have been shown to be independent of lithium ion concentration in aqueous phase and the type of extracted salt anion but depend only on the type and size of crown ether ring.     

Synergistic extraction of manganese(II) with thenoyltrifluoroacetone and neutral unidentate and bidentate ligands

Tritium content in tritiated titanium was measured by the method of fluorescent X-ray detection with an intrinsic Ge detector. The conventional method of setting region-of-interest of overlapped X-ray peaks was developed. The Ti K and K X-ray peak profile of³H/Ti was compared with that of V-49 electron capture standard source. Effect of geometry and sample thickness on peak profile was discussed. Detection limit in this method was 0.187 GBq of tritium.     

Ion-pair extraction of uranyl ion from aqueous medium using crown ethers

Ion-pair extraction behaviour of uranyl ion from aqueous solutions was studied at pH 3.0 employing crown ethers viz. benzo 15 crown 5 (B15C5), 18 crown 6 (18C6), dibenzo 18 crown 6 (DB18C6), and dibenzo 24 crown 8 (DB24C8) in chloroform as the organic phase and picric acid as the organophilic counter anion. The stoichiometry of the extracted species corresponded to [UO₂(crown ether)_n]²⁺·[pic⁻]₂ where n=1.5 for benzo 15 crown 5 and 1 for 18 crown 6 as well as dibenzo 18 crown 6. Adducts of DB24C8 could not be observed as practically no extraction was possible using this reagent. The separation behaviour of fission products from an irradiated uranium target was also studied. An interesting observation on the separation of trivalent lanthanides from uranyl ion is reported.     

Self-assembled monolayers of crown ethers for solid phase extraction in flow-injection analysis

Modification of a gold electrode with 2-[(6-mercaptohexyl)oxy]methyl-15-crown-5 yielded a self-assembled monolayer (SAM), CESAM, that preconcentrated Pb(II) from aqueous solution. With a 20 h modification, measurements by the copper underpotential deposition method showed that the fraction of the surface covered, Θ, was 0.99. Proof-of-concept was obtained for an analytical strategy in which the Pb(II)-CESAM was released into a flow stream by electrochemical oxidation of the gold thiolate and detected amperometrically. A detection limit of 6 pmol Pb(II) was estimated from the signal-to-noise ratio. Electrochemical release into a flow injection analysis system with detection by argon inductively coupled plasma spectroscopy provided detection of 0.2 nmol Pb(II) in a 200 μL injection. Analytical utility requires rapid, reproducible renewal of the CESAM. With 30-90 s modifications, Θ=0.97±0.01 and was independent of modification time over that range.     

Synergistic extraction of Am(III), Th(IV) and U(VI) by PMBP and crown ethers

The extraction of UO ₂ ²⁺ , Am³⁺, and Th⁴⁺ by 1-phenyl-3-methyl-4-benzylpyrazolone with crown ethers was studies using 0.1M (NaClO₄) aqueous phase and toluene. The crown ethers were 12C4, 15C5, 18C6, DB18C6 and DCH18C6. The synergic equilibrium constant did not show correlation between the cationic radii and the ether cavity size nor did the values follow a simple order of ether basicity. The ether basicity, steric effects, and the number of ether oxygens bound to the cation are the combined factors which seemingly determine the pattern of M(PMBP)_n—CE interaction.     

Synergistic extraction of cobalt(II) from cesium containing aqueous solutions with mixtures of 4-acyl-pyrazol-5-ols and crown ethers

The synergistic extraction of cobalt(II) from aqueous solutions loaded with cesium chloride or nitrate, with mixtures of 1-phenyl-3-methyl-4-acyl-pyrazol-5-ols (HL) [acyl = benzoyl (HPMBP), para-tert.-butyl-benzoyl (HPMB'P), stearoyl (HPMSP)] and crown ethers E = B15C5, 18C6, DC18C6, DB18C6 and DB24C8 (DC = dicyclohexano, B = benzo, DB = dibenzo), in CHCl(3), CH(2)Cl(2) and ClCH(2)CH(2)Cl, has been studied. The experimental data agree with the extracted species E(2)CsCoL(3) (E = B15C5), ECsCoL(3), (E = DB18C6) and CoL(2)E (E = DB24C8). The extraction yields follow the orders: 18C6 DC18C6 > DB18C6 > B15C5 > DB24C8, HPMBP > HPMB'P > HPMSP, and ClCH(2)CH(2)Cl > CH(2)Cl(2) > CHCl(3). In spite of the better complexation of potassium than cesium with "18C6" type crown ethers, the extraction of ECsCo (PMBP)(3) is generally higher than the EKCo(PMBP)(3) one. Except in the case of DB24C8, loading the aqueous phase with Cs(+), K(+), Sr(2+) or Ba(2+) improves the synergistic extraction of cobalt.     

Separation of thorium from lanthanides by solvent extraction with ionizable crown ethers

Thorium and the lanthanides are extracted by alpha-(sym-dibenzo-16-crown-5-oxy)acetic acid and its analogues in different pH ranges. At pH 4.5, Th is quantitatively extracted by the crown ether carboxylic acids into chloroform whereas the extraction of the lanthanides is negligible. Separation of Th from the lanthanides can be achieved by solvent extraction under this condition. The extraction does not require specific counteranions and is reversible with respect to pH. Trace amounts of Th in water can be quantitatively recovered using this extraction system for neutron activation analysis. The nature of the extracted Th complex and the mechanism of extraction are discussed.     

Ion-pair extraction of tetravalent plutonium from hydrochloric acid medium using crown ethers

Ion-pair extraction behaviour of plutonium (IV) from varying concentrations of HCl solution was studied employing crown ethers (benzo-l5-crown-5 (B15C5), 18-crown-6, (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexano-18-crown-6, (DC18C6), dibenzo-24-crown-8 (DB24C8) and dicyclohexano-24-crown-8 (DCH24C8)) in nitrobenzene as the extractant. Ammonium metavanidate was used as the holding oxidant in the aqueous phase and the conditions necessary for the quantitative extraction of the tetravalent ion were found. The co-extraction of species of the type [HL⁺].[HPu(Cl) ₆ ^– ] and [HL⁺]2·[Pu(Cl) ₆ ^2– ] as ion-pairs (where L represents the crown ether) is suggested.