Alternative radiochemical heavy ion activation methods for the production and separation of thallium radionuclides

Converter target chemistry - A new challenge to radioanalytical chemistry

The 1-2 GeV proton induced spallation reaction on the high Z materials like Hg, or lead bismuth eutectic (LBE), popularly known as converter targets, will produce strong flux of fast neutrons which would further react with fissile materials to produce intense radioactive ion beam (RIB). LBE offers suitability for use as converters over Hg but it suffers from the demerit of radiotoxic polonium production. These targets may be viewed as a store house of clinically important and other exotic radionuclides. For application of those radionuclides, radiochemical separation from bulk target material is of utmost importance.

Separation of 195(m,g),197mHg from bulk gold target by liquid-liquid extraction using hydrophobic ionic liquids

The 195(m,g),197mHg radionuclides were produced in accelerator when natural Au foil was irradiated with 23 MeV protons. The no-carrier-added (NCA) Hg radioisotopes were separated from the bulk Au target by liquid-liquid extraction (LLX) employing hydrophobic RTILs 1-butyl-3-methylimidazolium hexafluorophosphate([C4mim][PF6]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([bmim][Tf2N]) as extractant with HNO3 and HCl. In each case, bulk Au was extracted into the RTIL phase leaving NCA Hg-radionuclides in the aqueous phase. The RTILs were recovered by washing with 1 M K2S2O5 and freshly prepared 1 M FeSO4. The reported separation methods follow green chemistry approach as it does not involve any volatile reagents.

Separation of no-carrier-added 203Pb, a surrogate radioisotope, from proton irradiated natTl2CO3 target using calcium alginate hydrogel beads

203Pb is a promising radioisotope in the field of medical science as an imaging surrogate of 212Pb. In the present investigation 203Pb was produced by proton irradiation of natural Tl2CO3 target and was separated from the bulk Tl target using calcium alginate (CA) hydrogel beads with a high separation factor (3.8×104 at 10−3 M HNO3). During the separation process 203Pb was encapsulated in CA beads and desorption of the radioisotope could only be achieved in 1M HNO3. Possibility of Tl uptake was also checked in Fe doped CA (Fe-CA) beads after oxidation of Tl(I) to Tl(III) by sodium bismuthate. No significant uptake of Tl(III) was noticed in the Fe-CA beads. The matrix is therefore suitable for isolation of 203Pb from the target as well as its storage in the bead for therapeutic as well as diagnostic purpose.

Production and separation of no-carrier-added thallium isotopes from proton irradiated (nat)Hg₂Cl₂ matrix

For the first time, (nat)Hg₂Cl₂ target has been used to produce no-carrier-added-NCA (197,198,198m,199,200,201)Tl radionuclides using (nat)Hg(p,xn) reaction. Liquid-liquid extraction technique was employed in order to separate radiothallium from the bulk mercury matrix using liquid anion exchanger trioctylamine (TOA) dissolved in cyclohexane. In order to verify the presence of stable Hg in Tl fraction, the entire process was repeated with stable salts of Hg and Tl and the extent of separation was examined by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). High separation factors were observed both by radiometric and ICP-OES technique when 0.1 M HNO³ and 0.1M TOA were used as aqueous and organic phase, respectively. The Hg contamination was less than 0.3 ppm in the aqueous phase containing Tl after three times of extraction at the optimal condition.

Complexation study on no-carrier-added astatine with insulin: a candidate radiopharmaceutical

No-carrier-added astatine radionuclides produced in the (7)Li-irradiated lead matrix were separated from bulk lead nitrate target by complexing At with insulin, followed by dialysis. The method offers simultaneous separation of At from lead as well as its complexation with insulin. The At-insulin complex might be a potential radiopharmaceutical in the treatment of hepatocellular carcinoma. The stability of At-insulin complex was checked by dialysis against deionized water and Ringer lactate (RL) solution. It has been found that the half-life of At-insulin complex is about approximately 12h, when dialyzed against deionized water and is only 6h, when dialyzed against RL solution having the same composition as blood serum. The 6h half-life of this Insulin-At complex is perfect for killing cancer cells from external cell surfaces as the half-life of internalization of insulin molecule inside the cell is 7-12h.

Production and separation of Astatine Radionuclides: some new addition to Astatine Chemistry

For the first time no-carrier-added (nca) (209,210)At radionuclides were produced by heavy ion ((7)Li) activation from 4 mg/cm(2) lead nitrate target. Astatine was separated from the bulk target by three different approaches. Nca astatine radionuclide was selectively partitioned in the (i) polymer rich phase of an aqueous biphasic system consisting of polyethylene glycol (PEG) 4000 (50% w/w) and 2M Na(2)SO(4) solution (ii) aqueous phase of a liquid liquid extraction system being comprised of a liquid cation exchanger, HDEHP (di-2-ethylhexyl phosphoric acid) (0.5%) and liquor ammonia (iii) liquid phase of a solid liquid extraction system of cation exchange resin Dowex-50 and 10(-6)M HCl. Very high separation factors have been achieved in all the three methods.

Radiochemical separation of carrier-free 204,206 Bi from alpha-irradiated thallium oxide target

Alpha activation of Tl(2)O(3) target results in the formation of carrier-free 204,206 Bi. Two different radiochemical methods were used for the separation of bismuth radionuclides from the target matrix. A very high separation factor was achieved using liquid-liquid extraction (LLX) method with methyl isobutyl ketone (MIBK)-HCl system. Solid-liquid exchange adsorption was carried out using a novel inorganic ion exchanger, zirconium vanadate from HCl medium. The separation was found to be maximum around pH 2.