Authors:M. Shehata, B. Scholten, I. Spahn, H. Coenen, and S. Qaim
A method for the separation of no-carrier-added arsenic radionuclides from the bulk amount of proton-irradiated GeO2 targets as well as from coproduced radiogallium was developed. The radionuclides 69Ge and 67Ga produced during irradiation of GeO2 were used as tracers for Ge and Ga in the experiments. After dissolution of the target the ratio of As(III) to As(V) was
determined via thin layer chromatography (TLC). The extraction of radioarsenic by different organic solvents from acid solutions
containing alkali iodide was studied and optimized. The influence of the concentration of various acids (HCl, HClO4, HNO3, HBr, H2SO4) as well as of KI was studied using cyclohexane. The optimum separation of radioarsenic was achieved using cyclohexane with
4.75 M HCl and 0.5 M KI and its back-extraction with a 0.1% H2O2 solution. The separation leads to high purity radioarsenic containing no radiogallium and <0.001% [69Ge]Ge. The overall radiochemical yield is 93 ± 3%. The practical application of the optimized procedure in the production
of 71As and 72As is demonstrated and batch yields achieved were in the range of 75–84% of the theoretical values.
Authors:M. Shehata, B. Scholten, I. Spahn, S. Qaim, and H. Coenen
The radiochemical separation of radiogallium from radiogermanium was studied using ion-exchange chromatography (Amberlite
IR-120) and solvent extraction (Aliquat 336 in o-xylene). Both Amberlite IR-120 and Aliquat 336 in o-xylene have been used for the first time in separations involving radiogallium and radiogermanium. For tracer studies the
radionuclides 68Ge (t1/2 = 270.8 days), 69Ge (t1/2 = 39 h) and 67Ga (t1/2 = 78.3 h) were used. They were produced by the nuclear reactions natGa(p,xn)68,69Ge and natZn(p,xn)67Ga, respectively, and separated from their target materials in no-carrier-added form. Several factors affecting the separation
of radiogallium from radiogermanium were studied and for each procedure the optimum conditions were determined. The solvent
extraction using Aliquat 336 was found to be better. The separation yield of radiogallium was >95%, the time of separation
short, the contamination from radiogermanium <0.008% and the final product was obtained in 0.5 M KOH. This method was adapted
to the separation of n.c.a. 68Ga from its parent n.c.a. 68Ge. The quality of the product thus obtained is discussed.
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.
Authors:S. Kandil, B. Scholten, Z. Saleh, A. Youssef, S. Qaim, and H. Coenen
The radiochemical separation of no-carrier-added zirconium from proton irradiated yttrium was studied by two techniques, namely,
ion-exchange chromatography using Dowex 50W-X8 and Dowex 21K resins, and solvent extraction using HDEHP and TPPO, the latter
reagent being employed for the first time for separation of radiozirconium from bulk of yttrium. Out of all those techniques,
the solvent extraction using TPPO was found to be the best: the separation yield of radiozirconium was >97%, the time of separation
was short, the contamination from the long-lived 88Y activity was low (10−4%) and the final product was obtained in the form of oxalate. The production of 89Zr and 88Zr of high radionuclidic and chemical purity via irradiation of yttrium targets with protons of energies 12 and 20 MeV, respectively,
is described. The experimental yields of the two radionuclides were found to be 28 MBq/μA·h and 1.63 MBq/μA·h, respectively.
Each value corresponds to about 80% of the respective theoretical yield.
Authors:A. El-Mohty, M. El-Kolaly, M. Raieh, H. Coenen, and G. Stocklin
A method for radiopharmaceutical preparation of L-6-[123I]-iodo-m-tyrosine a potential SPECT brain imaging agent is described. The method is based on direct electrophilic radioiodination of L-m-tyrosine with [123I] NaI/chloramine-T (CAT) and small amount of KI as a carrier at pH 1.0 where L-6-[123I]-iodo-m-tyrosine is the predominant isomer. A high radiochemical yield of L-6-[123I]-iodo-m-tyrosine up to 70% has been achieved by adding small amount of KI (0.001 g) as a carrier to the reaction mixture. The pure 6-isomer was separated by reverse phase radio high pressure liquid chromatography (HPLC) on RP-18 column using 0.02M sodium acetate/ethanol (9010) adjusted to pH 3.9 with glacial acetic acid at a flow rate 2 ml/min. According to the signals of the UV detector (=254) the 6-isomer was eluted at a retention time 12.5 minutes,K=6. The eluted fraction of L-6-[123I]-m-tyrosine pooled together, evaporated under reduced pressure, then dissolved in 5 ml isotonic phosphate buffer and sterilized by passing through 0.22 m millipore filter. The sterile solution was now ready for nuclear medical applications. The biological distribution of L-6-[123I]-iodo-m-tyrosine in mice was studied. The results showed that 3% of the injected dose is taken up in dopamine rich striatum 30 minutes after injection and not in norepinephrine-rich hypothalamus.