Synthesis and extraction studies with a rationally designed diamide ligand selective to actinide(iv) pertinent to the plutonium uranium redox extraction process.

A new class of conformationally constrained oxa-bridged tricyclo-dicarboxamide (OTDA) ligand was rationally designed for the selective extraction of tetravalent actinides pertinent to the Plutonium Uranium Redox EXtraction (PUREX) process. Two of the designed diamide ligands were synthesized and extraction studies were performed for Pu(iv) from HNO3 medium. The mechanism of extraction was investigated by studying various parameters such as feed HNO3, NaNO3 and OTDA concentrations. The nature of the extracted species was found to be [Pu(NO3)4(OTDA)]. One of the OTDA ligands was elaborately tested and showed the selective extraction of Pu(iv) and Np(iv) over other actinide species, viz., U(vi), Np(v), Am(iii), lanthanides and fission products contained in a nuclear waste from the PUREX process. DFT calculations predicted the charge density on each of the coordinating 'O' atoms of OTDA supporting its high Pu(iv) selectivity over other ions studied and also provided the energy optimized structure of OTDA and its Pu(iv) complex.

Design, synthesis and extraction studies of a new class of conformationally constrained (N,N,N',N'-tetraalkyl)7-oxabicyclo[2.2.1]heptane-2,3-dicarboxamides.

A new class of conformationally constrained 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxamides (OBDA) of three secondary amines was synthesized, and their extraction behavior for trivalent and tetravalent actinides in HNO3 medium was studied. Amongst the diamides, N,N-bis-2-ethylhexyl substituted diamide showed the best results for actinide extraction. This diamide also exhibited a very low level of extraction for Sr(ii) and Ru(iii) which is desirable, thus providing higher selectivity for actinides. The stripping of extracted metal ions was achieved using 0.1 M oxalic acid for Pu(iv) or pH ∼ 2 solution for Am(iii). Third phase formation was not observed for the OBDA ligand even for a higher concentration of Eu up to 5 g L(-1) with retention of good DEu. The tridentate nature of the OBDA ligand was ascertained by studying the IR and NMR spectra of the Eu(iii) complex with the ligand. The OBDA showed the formation of a mixture of mono- and di-solvated species of Eu(iii) as indicated by the slope analysis method and ESI-MS. Density functional theoretical (DFT) study was carried out to determine the energy optimized structure of the free ligand and its Am(3+) complex.

Extraction and structural studies of an unexplored monoamide, N,N'-dioctyl, α-hydroxy acetamide with lanthanide(III) and actinide(III) ions.

A monoamide, N,N'-dioctyl, α-hydroxy acetamide, shows unusual extraction properties towards trivalent lanthanide and actinide ions above 3 M HNO3. The extracted ions could be quantitatively back extracted using 0.5 M HNO3. This amide shows negligible extraction towards Sr(II) and Ru(III) ions, making it advantageous over other reported extractants. The structures of Sm(III) and Eu(III) nitrate compounds show that the metal ion is surrounded by three of the ligands, one nitrate and one water molecule. The ligand acts as a neutral bidentate ligand and bonds through the amido and hydroxyl oxygen atoms.

Extraction paper chromatography technique for the radionuclidic purity evaluation of 90Y for clinical use.

Yttrium-90 used for therapy should be of very high radionuclidic (RN) purity (>99.998%) as the most probable contaminant, strontium-90, is a bone seeker with a maximum permissible body burden of 74 kBq (2 microCi) only. None of the current known methods of RN purity estimations is adequate to reliably measure the 90Sr RN impurity at such low levels. Our aim was to develop a reliable technique to accurately determine the amount of 90Sr in 90Y used for therapy. This new technique combines chelate-based extraction with paper chromatography using paper impregnated with 2-ethylhexyl, 2-ethylhexylphosphonic acid (KSM-17), which is a 90Y-specific chelator. A PC strip impregnated with KSM-17 at the point of spotting is used for chromatography. Upon development with normal saline, 90Sr moves to the solvent front leaving 90Y completely chelated and retained at the point of spotting. The activity at the solvent front (90Sr) is quantified by liquid scintillation counting, and the data are compared with the total applied activity to provide the RN purity of the test solution. The method has a sensitivity of > or =74 kBq (2 microCi) of 90Sr per 37 GBq (1 Ci) of 90Y. This novel, innovative, and simple technique offers a reliable solution to the unanswered problem of estimation of 90Sr content in 90Y used for cancer therapy.

Evaluation of 90Y phosphate particles as a possible radiation synoviorthesis agent.

BACKGROUND: 90Y is one of the radioisotopes used extensively for therapy due to its favourable nuclear characteristics. Particles and colloids incorporating 90Y are being used for radiation synovectomy, especially in European countries. METHODS: In our present work, 90Y phosphate particles were prepared and evaluated for use in radiation synovectomy. The radioactive particles were prepared by reacting carrier added 90YCl3 with phosphoric acid. RESULTS: The radiolabelling yield obtained was >95%. The particles were found to be stable in saline for up to 7 days of study at 37 degrees C. Particle size analysis of inactive yttrium phosphate showed that most of the particles were in the size range of 2-20 microm. Biodistribution studies carried out by intra-articular injection of the particles into the knee joints of rats showed that approximately 99% of the particles were retained in the joints with negligible radioactivity in the major organs even at 48 h post-injection. Scintigraphic studies in rabbit showed that >99% of the radioactive particles were retained in the knee joint even at 96 h post-injection. No significant radioactivity above background was detected in the blood. CONCLUSION: The promising results warrant further studies on 90Y phosphate particles for use in radiation synovectomy.