الفهرس 
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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.