The effect of temperature on the extraction of the trivalent actinides Am3+, Cm3+ and Cf3+ with the liquid cation exchanger dinonylnaphthalenesulphonic acid (HD) in toluene is studied. The different thermodynamic
functions of this system are determined from the experimental results. It is found that the free energy variation for the
extraction of these metal ions by HD is mainly determined by the entropic terms arising from the hydration-dehydration process
of the exchanged ions.
Extraction of lanthanides and actinides were found to be synergically enhanced by a mixture of bis/2-ethyl hexyl/phosphoric acid /HA/ and dinonylnaphthalene sulfonic acid /HD/ in aromatic diluents covering a wide range of dielectric constant. The main extracted species is found to be in the form MA2Hm–1Dm. Experimental results indicate that the extraction mechanism is governed by the extraction of HD in the organic phase.
The thermodynamic functions for the extraction of Sc3+ by liquid cation exchangers HD and HDEHP are determined radiometrically by the temperature coefficient method. The role of
diluent dielectric constant on the extraction of Sc3+ by HD is also studied. The thermodynamic parameters determined indicated that the free energy variation for the extraction
of Sc3+ by HD is mainly determined by the entropic terms arising from the hydration—dehydration process of the exchanged ions. In
the case of HDEHP as extractant, the free energy variations are determined mainly by the entalpic terms of the system.
Authors:M. El-Absy, M. El-Enein, M. Raieh, and H. Aly
12-molybdocerate(IV) gel labelled with99Mo has been prepared via isotope exchange between a column of inactive molybdate matrix and a mobile solution of99-Mo-sodium molybdate(VI) in 0.1 mol·dm–3 HNO3. The composition and nature of the reaction mixture, concentration of Mo(VI) in the reactants, reaction temperature and/or drying temperature of the gel matrix on the exchange yeild of99Mo and time of reaction are explored using the batch equilibration and/or the chromatographic column methods. The obtained material is evaluated for use in preparation of elution-type99Mo-99mTc generators.
The extractability of99Mo-molybdophosphoric acid H3/PMo12O40/ and99mTc-pertechnetic acid /PTcO4/ in 20% (v/v) bis /2-ethylhexyl/ phosphoric acid /HDEHP/ in benzene has been investigated at different concentrations of HCl, HBr and HNO3 acids. The effect of extractant concentration and diluent on the extractability of molybdophosphoric and pertechnetic acids with 20% (v/v) HDEHP in benzene from different concentrations of HCl acid has also been studied.99Mo-molybdo-phosphoric acid was found to be selectively extracted and separated from99mTc-pertechnetic acid with 20% HDEHP in benzene at an acidity of about 0.49M HCl, HBr and HNO3. The extractability of H3/PMo12O40/ from these acids generally follows the decreasing order HBr>HCl>HNO3. The separation factors /Kd molybdophosphoric/Kd pertechnetic/ were found to be 12.9×105 and 7.6×105 for HBr and HCl, respectively. The extractability of pertechnetic acid follows the order HCl>HBrHNO3. Benzene is the diluent due to its radiation stability. A new procedure for the separation of99mTc from99Mo was suggested.
Authors:H. Aly, M. El-Dessouky, M. Raieh, and S. Mohamed
Synergic extraction of trivalent iron and cobalt with thenoyltriflouroacetone (HTTA) and the synergic bases (B) benzylamine
(BA), dibenzylamine (DBA) and tribenzylamine (TBA) was studied. The extracted adducts proved to have the general formula M(TTA)3·B for all the amines investigated. The formation constants of the mixed-ligand complexes decrease in the order DBA>TBA>BA.
While equilibrium constant β3,1 for the Co(TTA)3·DBA complex is higher than the corresponding iron adduct, β3,1 for the iron adducts with BA and TBA are higher than those for cobalt.
Authors:H. Aly, M. Raieh, S. Mohamed, and A. Abdel-Rassoul
The effect of ten pure diluents and different mixtures of nitrobenzene and toluene on the synergic extraction of Co2+ by the thenoyltrifluoroacetone (HTTA)-tribenzylamine (TBA) mixture is studied. The logarithm of the extraction constant of
Co(TTA)2 increases with increasing dielectric constant of the diluent, whereas the logarithm of the formation constant of the extracted
adduct Co(TTA)2TBA decreases with increasing dielectric constant of the diluent. This behaviour is explained by changes in the hydrophobic
character of the extracted species. The theory of regular solutions is successfully applied to the extracted adduct. Consideration
of the self-association of the amine salt is necessary in the treatment of the equilibria involved.
Authors:H. Aly, M. Raieh, S. Mohamed, and A. Abdel-Rassoul
The solvent extraction of divalent iron, cobalt, copper and zinc from perchlorate medium of constant ionic strength (0.1 H+, NaClO4) into a mixture of thenoyltrifluoroacetone (HTTA) and dibenzylamine (DBA) in chloroform has been studied. The extraction
of the different cations were found to increase by more than 103 order of magnitude in presence of DBA. Slope analysis of the extraction results assumed a general formula of M(TTA)2·DBA for the extractable adduct. A stability order of Fe(TTA)2·DBA>Co(TTA)2 ·DBA>Zn(TTA)2·DBA>Cu(TTA)2·DBA has been decumented.
Authors:A. El-Mohty, A. El-Wetery, M. El-Kolaly, and M. Raieh
A modified method for the preparation of L-[131/123I] iodotyrosine as a brain imaging agent is described. The method is based on direct electrophilic radioiodination of L-tyrosine with NaI [131/123I] using chloramine-T (CAT) and 0.001 g KI as a carrier at pH 7.0. The product was purified by reverse phase high performance liquid chromatography (HPLC). A high radiochemical yield up to 85% of L-[131/123I] iodotyrosine has been achieved with radiochemical purity of greater than 97%. The relation between the pKa of L-tyrosine and pH of the reaction medium was calculated in order to correlate the radiochemical yield of L-[131/123I] iodotyrosine and the state of the three ionizable groups of L-tyrosine. Also, the influence of the reaction conditions on the radiochemical yield of L-[131/123I] iodotyrosine was investigated.
Authors:A. El-Mohty, M. El Kolaly, M. Raieh, H. Coenen, and G. Stocklin
L-3-[123I] iodo--methyltyrosine has been reported to have a high affinity for a transport system in the blood-brain-barrier (BBB). Synthesis of L-3-[123/131I] iodo--methyltyrosine was performed by direct electrophilic iodination starting with no carrier added (n.c.a)131I or123I in the presence of oxidizing agent. Different oxidizing agents have been tested and the different factors affecting the radiochemical yield of L-3-[123I] iodo--methyltyrosine have been investigated. A method of pharmaceutical preparation of L-3-[123I] iodo--methyltyrosine ready for medical applications has been described. Among the oxidizing agents tested, iodogen in phosphate buffer at pH 7 seems to be the best which gives high radiochemical yield (85%) within 5 minute reaction time at room temperature in the presence of small amount KI (0.001 g) as a carrier. The radioactive impurities and side chlorinated by-product which have been found in case of iodination by chloramine-T (CAT), KIO3 and H2O2 methods disappear in case of iodogen method. The labelled product was separated and purified by radio high pressure liquid chromatography (HPLC) using methanolwateracetic acid (20801) as eluant at a flow rate 1.0 ml/min. According to the signals of the detectors the fractions of L-3-[123I] iodo--methyltyrosine were collected, evaporated to complete dryness and the residue dissolved in isotonic phosphate buffer pH 7.4. The product was sterilized by passing through 0.22 m millipore filter and the radiopharmaceutical was now ready for nuclear medical application.