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Abstract SUMMARY The thesis entitled ”Molybdenum-99/Technetium-99m Generators Based on Alumina Gel” comprises three chapters; introduction, experimental, and results and discussion. Chapter 1; is the introduction. It includes brief accounts on the applications of 99mTc generators, chemistry and radiochemistry of molybdenum and technetium, chemistry of aluminum, methods of production of molybdenum-99 radionuclide, activation molybdenum-99 cross-contaminant radionuclides, purification process, 99Mo/99mTc gel generators, and molybdate (VI) gel matrices. Chapter 2; is the experimental part. It includes chemicals and equipments used in this study, for preparation of high purity gel type 99Mo/99mTc generator from activation 99Mo. Preparation of simulated Al wrapped molybdenum trioxide targets for irradiation in nuclear reactor and dissolution in concentrated NaOH to obtain mixture solutions of aluminate/99Mo-molybdate (VI). Precipitation of the alumina 99Mo-molybdate (VI) gel matrix via acidification of the hot mixture solution with concentrated HNO3 acid. The adsorption yield of 99Mo onto the precipitated alumina polymer was radiometrically studied (using Multichannel Analyser) from different acid media, such as HNO3, HCl and H2SO4 at constant pH 5.5 and at different pH values 4.5, 5.5, 6.5, 7.5, 8.5 and 9.5 from NO3 - media. Physico-chemical investigations of the prepared AlMo gels and alumina polymers by radiometric analysis, IR, TGA, DTA and reaction mixture solutions temperature and pH value. Elution performance of 99mTc from Al99Mo gel matrices containing ~ 5-10 mCi 99Mo, packed in the form of chromatographic columns eluted each with 0.9 % NaCl solution. Quality control inndices of the 99mTc eluates from the prepared columns including: elution curve, elution yield (using radioisotope calibrator), radionuclidic purity (using MCA and NaI(Tl) counter), radiochemical purity (paper chromatography methanol) and chemical purities (Mo spectrophotometricaly, Al spot test and Fe by ICP). Purification of aluminate/99Mo-molybdate (VI) solution from contaminant radionuclides by oxidation of Fe (II) to Fe (III) using H2O2 to Fe (III). Preparation of 99Mo / 99mTc generators based on purified Al99Mo gel and quality control indices of the 99mTc eluates. Chapter 3; is the results and discussion. This chapter includes in a systematic mode the results and discussion of Al99Mo gel matrix preparation from unpurified and radiocontaminant purified molybdenum-99/aluminate mixture solutions. The Al99Mo gels were packed in the form of chromatographic columns for elution of the generated 99mTc radionuclide with physiological 0.9 % NaCl solution suitable for use in nuclear medicine. Preparation of unpurified AlMo gel. Accurate amounts of molybdenum trioxide powder (1.0 g MoO3) tagged with 5-10 mCi 99Mo and 1.2 g Al foil were dissolved in 30 ml ~ 5 M NaOH solution. After complete dissolution (~ 15 min), the product aluminate/99Mo-molybdate (VI) mixture solution was treated with 0.5 ml 30 w/v % H2O2 and then acidified with concentrated HNO3 (68 w/v %), while stirring, till at pH 5.5. The formed precipitate of alumina 99Mo-molybdate gel matrix (Al99Mo) was separated by filtration. The adsorption yield of 99Mo-molybdate (VI) anions onto the formed aluminum hydroxide base was radiometrically determined and the adsorption yield was calculated from the difference between 99Mo radiactivity in the mixture solution and supernatant. The adsorption yield of 99Mo (VI) was found to be ~97.5%. The effect of acid radical and pH value on the adsorption yield of 99Mo (VI) anions were studied from HNO3, HCl and/or H2SO4 acid solutions at constant pH 5.5 and variable pH values 4.5, 5.5, 6.5, 7.5, 8.5 and 9.5, respectively. The adsorption yields of 99Mo were founds to be 97.5, 94 and 87% 99Mo-paramolybdate (VI) from HNO3, HCl and H2SO4 acid media at pH 5.5, respectively. The adsorption of 99Mo-molybdate (VI) anions was studied at different pH value, 4.5, 5.5, 6.5, 7.5, 8.5 and 9.5, by addition of concentrated HNO3 acid to similar aluminate/99Momolybdate (VI) mixture solutions. The adsorption yield of ~ 97.5 % at pH 5.5 was decreased to ~ 92.5% at pH 4.5. As well as, it was gradually decreased from 97.5% to ~ 4 % with increasing the pH value from 5.5 to 9.5, respectively. Physico-chemical investigations, such as radiometric analysis and supernatants measurments of pH value and temperature, IR spectra, dehydration, simultaneous DTA and TGA for inactive alumina polymer and AlMo gel matrices indicated that the alumina polymer: pseudoboehmite γ-AlOOH was first in-situ precipitated from the mixture solutions. Thereafter, Mo (VI) anions were adsorbed on the surfaces of the alumina polymers to form the corresponding alumina 99Mo-molybdate (VI) gel matrices. Gel matrices prepared from acidic solutions exhibited higher Mo(VI) content and chemical stability than from basic solutions. Finally, the separated Al99Mo gel was washed with 40 ml 3.5 M NaNO3 solution (pH 5.5) and 50 ml H2O. Then, it was dried for ~ 24 h at 50 oC in an air electric furnace, crushed in an agate mortar and sieved to ~ 0.15 - 0.8 mm particles size suitable for chromatographic column preparations. Elution performance of the generated 99mTc radionuclide. Equal amounts each of 2.0 g Al99Mo gel matrices (containing ~ 5 mCi 99Mo) were identically packed in the form of chromatographic columns (1.0 cm i.d) from 0.9% NaCl solution. Elution of 99mTc from the column was carried out on the next day with passing 10 ml saline solution at a flow rate of 1.0 ml/min. The corresponding elution yield, elution profile and other Q.C. indices of 99mTc elution performance were investigated. Elution yield of 99mTc generated onto Al99Mo gel matrices prepared from NO3 - and Cl- media at pH 5.5 were found to be 78 and 88%, respectively. Also, Elution yields of 99mTc from Al99Mo gel matrices prepared from NO3 - media at pH values 4.5, 6.5 and 7.5 were found to be 86, 78 and 76, respectively,99mTc elution from.Al99Mo gel matrices prepared from H2SO4 media, was not conducted due to peptization of the matrix in the eluent. Matrices precipitated from NO3 - solutions at pH 8.5 and 9.5 were not considered because of low 99Mo adsorption. The higher the attraction forces between the alumina polymer and the molybdate (VI) anions unit structure: Mo7O24 6- > Mo8O26 4- > MoO4 2- the lower was the release of Mo into the 99mTc eluates (pH 5.5 < 4.5 < 6.5), respectively. High Mo release not only decreased the CP but also RN due to increase of 99Mo (i.e, % breakthrough) in the 99mTc eluate. Dissociation of the octa- and para-molybdates (VI) to MoO4 2- increased the 99mTc eluate H+-ion concentration: Mo8O26 4- > Mo7O24 6-. The AlMo matrix synthesised from NO3 - solution at pH 5.5 has the highest RN ( 99.92 % 99mTc). Radiochemical purity of 99mTc eluates was of ~ 97.8, 98.1, 94.2 and 91.4 % TcO4 - from AlMo matrices prepared at pH values,4.5,5.5, 6.5 and 7.5, respectively, and markedly decreased with increasing the preparative pH value: pH 5.5 ~ 4.5 > 6.5 > 7.5, respectively. Chemical purity of 99mTc eluates, the presence of Al in the 99mTc eluates from Al99Mo gels prepared from NO3 - media at different pH value 4.6, 5.5, 6.5 and 7.5. were found to be ~ 5.0 μg/ml. Molybdenum concentration in the eluates was determined spectrophotometrically by the thiocyanate method. Mo concentration in the 99mTc eluate from Al99Mo gel prepared from NO3 - solution at pH values 4.5, 5.5, 6.5 and 7.5 were found to be ~ 3,1.0, 5.0 and 5.0 μg/ml, respectively. highly pure Al99Mo gel matrices were used in preparation of 99Mo/99mTc generators. Radiometric analysis of the 99mTc eluates (from 99Mo/99mTc generators using unpurified alumina99Mo-molybdate (VI) gel matrix precipitated at pH value 5.5 by addition of HNO3 acid) were measured for 1000 s after a decay period of 5 d. Gamma-ray spectra of the residual elutes were contaminated with different radionuclide impurities such as 95Zr, 95Nb, 103Ru, 124Sb, 125Sb and 125Sn. So, aluminat/99Momolybdate mixture solutions must be purified before precipitation of the AlMo gel matrix for use as 99Mo/99mTc generator. Purified alumina 99Mo-molubdate gel matrices were prepared in two sequential steps namely, purification and precipitation: To decrease the problem of exhausted generators storage and the patients absorbed dose. For preparation of the starting radiotracer mixture solution, accurate amount of 1.0 g MoO3 tagged with 10 mCi 99Mo, 1.2 g Al foil (containing ~ 2.74 mg Fe) and 120 mg FeCl3.6H2O were dissolved in 30 ml 5 M NaOH solution. The exothermic dissolution reaction was completed in ~ 15 min with evolution of H2 gas. The final alkali concentration was found to be ~ 4 M NaOH. Gamma-ray spectra of the aluminate/99Mo- Molybdate/Fe(II) hydroxide mixture solution measured immediately after preparation and after a decay period of 60 d indicated that well-detected gamma-ray energy peaks of apparently pure 99Mo overlapped the characteristic energy peaks of the interfering cross-contaminant radionuclides: 95Nb, 95Zr, 103Ru, 124Sb, 125Sb and 125Sn. 0.5 ml H2O2 was added to the aluminate/99Mo-Molybdate/Fe(II) hydroxide mixture solution to oxidize soluble Fe (OH)3 ⎯ into insoluble Fe(III) minerals and to insure oxidation of radiation reduced 99Mo species to Mo (VI) species, if activation 99Mo was used. After complete addition of H2O2, the formed ferric hydroxide Fe(OH)3 precipitate sustained in the supernatant containing soluble sodium aluminate and molybdate (VI) mixture solution. Gamma-ray spectroscopy of the supernatant and the formed Fe(III) mineral precipitate showed that contaminant radionuclides were preferentially transformed into the formed precipitate. For assessment of the purification process, Iron (III) minerals were precipitated from 33 ml aluminate/99Mo-molybdate mixture solutions containing 0.146, 0.476, 0.640, 0.807, 1.301, 1.45 and 2.1 x 10-2 M Fe(II) in ~ 4 M NaOH via oxidation with 0.5 ml H2O2. After standing for ~ 90 min, at ambient temperature, the reaction mixture solutions were centrifuged to collect and separate the formed Fe(III) minerals. Gamm-ray spectrometric analysis indicated that the elimination of radionuclides of 95Zr, 95Nb, 103Ru, 125Sb, 124Sb, and 125Sn were found to be 83, 96, 90, 20, 34 and 27 % respectively, with increasing the total concentration of Fe from 0.467 to 2.1 x10-2M. Decrease of 99Mo radioactivity in the supernatant showed the loss of ~ 0.5 % 99Mo due to adsorption onto the formed Fe(III) mineral of 2.74 mg Fe (i.e, from the Al foils). Loss of Mo on the precipitated Fe reach to maximium constant value of ~ 8.1 % 99Mo at ≥ 1.3 x 10-2 M Fe. Preparation of purified alumina 99Mo-molybdate (VI) gel matrices, Soluble sodium aluminate anions remained in the radionuclidic pure supernatant of aluminat/99Mo-molybdate (VI) after oxidation of soluble Fe(II) hydroxide by (from 120 mg FeCl3.6H2O) 0.5 ml H2O2 into an insoluble Fe(III) mineral together with the contaminant radionuclides. The formed Fe (III) minerals were separated by filtration. Aluminum oxyhydroxide i.e, pseudoboehmite was precipitated from the purified supernatant, by acidification with concentrated HNO3 at pH 5.5. Meanwhile normal molybdate (VI) anions MoO4 2- were condensed into paramolybdates (VI) Mo7O24 6- which preferentially transfered from the mixture solution via adsorption onto the surface of in-situ precipitated pseudoboehmite with a yield of ~ 97.5 % 99Mo-paramolybdates (VI) at pH 5.5. The separated alumina 99Mo-molybdate (VI) gel was thoroughly washed, dried and sieved to ~ 0.15 - 0.8 mm particles size suitable for chromatographic column operations as described above. 99mTc elution performance from 99Mo/99mTc generators based on purified alumina 99Mo-molybdate (VI) matrix chromatographic columns packed each with (2.0 g Al99Mo gel matrix tagged with ~ 5-10 mCi 99Mo were prepared and investigated for 99mTc elution in the usual way. Elution yield of the generated 99mTc radionuclide with 10 ml 0.9 % NaCl solution was found to be ~ 89.3 %. Radionuclidic purity of the 99mTc eluates (≥ 99.99% 99mTc) was determined by gamma-ray spectrometry and verified from the corresponding radioactivity decay curve . The corresponding radiochromatogram showed radiochemical purity ≥ 98.6 % TcO4 -. The presence of Al and Mo in the 99mTc eluates were found to be ~ 5.0 and 1.0 μg/ml, respectively. Fe content in 99mTc eluate was not detected (ICP analysis). The eluate pH value was in the range from 6.2 to 6.4 in agreement with high CP. It was found that 99mTc elution performance has reproducible elution yield with an average value of 89.5%, high RC and RN purity independent of the elution frequency and age of the generator (9 elutions over 12 days). 99mTc eluates the purified Al99Mo matrix are suitable for preparation of 99mTc of labelled pharmaceuticals, as well as 99mTc eluates from fission 99Mo loaded acidic alumina 99Mo/99mTc generators. |