Electrolysis: processes – compositions used therein – and methods – Electrolytic process involving actinide series elements or...
Patent
1996-07-09
1998-06-23
Phasge, Arun S.
Electrolysis: processes, compositions used therein, and methods
Electrolytic process involving actinide series elements or...
205688, 205702, 205755, 205760, B01D 5940, G21G 110
Patent
active
057700303
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This application is a 371 of PCT/DE95/00025 filed Jan. 10, 1995.
The invention relates to a process for the separation of carrier radio-free nuclides from liquid or liquefiable target materials of low electrical conductivity which, by means of a nuclear process, especially by cyclotron irradiation, are produced in ionizable or polarizable form, and within an electrode arrangement can be recovered by applying an electrical field for electrofixing the nuclide on one of the electrodes and from which the nuclide can be recovered after removal of the target liquid by supplying a solvent for further processing with a shut-off field or a field of opposite polarity by dissolution. The invention further relate to the use of this process and a flow cell suitable therefor.
BACKGROUND OF THE INVENTION
In the production of radiotracer compounds which play a significant role in medicinal diagnostics, especially short-lived radionuclides are used which should be provided as much as possible in carrier-free form.
As a result, there is a need to provide a process which is as time-conserving as is possible with the highest possible marker yield in spite of the carrier-free operation and which additionally because of the use of expensive target materials, should allow recovery as free from losses as is possible.
An especially elegant process for the recovery of radionuclides for radiotracer technology utilizes cyclotron irradiation of target material for which as an illustrative example the generation of .sup.18 F from .sup.18 O--H.sub.2 O can serve: .sup.18 F has a half life of about 110 minutes and is used, among other things, in the synthesis of .sup.18 F fluorodesoxyglucose for positron emission tomography. It is produced by cyclotron irradiation from .sup.18 O--H.sub.2 O which has a price contribution of about 150 German marks per gram to the process cost.
For about 8 years, the .sup.18 F fluoride formed in the cyclotron from .sup.18 O--H.sub.2 O has been separated by ion exchange whereby an .sup.18 O--H.sub.2 O loss as well as a contamination thereof by organic contents of the ion exchanger and .sup.16 O--H.sub.2 O admixtures by adherent moisture can arise.
There is also a procedure known wherein the target liquid, by the addition of basic phase transfer catalysts and/or carbonates, and .sup.18 F fluoride can be separated by distillation.
The aforedescribed processes have been found to be clearly unsatisfactory notwithstanding the fact that they have been in use for extended periods.
The process of the type described at the inception of the application has already been investigated by D. Alexoff et al (Appl. Radiat. Isot. Vol. 40, No. 1, pages 1-6, 1989) which describes an electrochemical cell with crucibles which fit one within the other and from which the inner platinum crucible, serving as a cathode, can be adjusted in height by means of a micrometer screw and the outer crucible, comprised of graphite or a vitreous carbon, is provided in a decomposable PVC holder and is arranged via a kind of jack for liquid exchange.
The direct current source is controllable between 0 to 20 volts with current amplitudes of up to 1 ampere. As far as possible, field strengths of 100 to 300 V/cm are used.
For the use of graphite crucibles, .sup.18 F yields of up to 70% are obtained. As a whole, cells with platinum electrodes and vitreous carbon electrodes have been found to be inefficient for routine production of large nuclide quantities and the ion-exchanger method has been preferred for this purpose.
SUMMARY OF THE INVENTION
By contrast, starting from the use of electrofixing mentioned at the outset, it has been found that an especially effective radionuclide separation from target material in a practically loss-free recovery of the latter and surprisingly higher yield of radionuclide is obtainable in a reduced time period by a process characterized in that it is carried out in a flow cell with a permanent electrode arrangement and the separation of the target liquid is effected while maintaining the f
REFERENCES:
patent: 4400250 (1983-08-01), Fairhurst
patent: 5425858 (1995-06-01), Farmer
patent: 5454924 (1995-10-01), Jansen et al.
Cell, by A. Lexoff et al., Appl. Radiat. Isot. vol. 40, No. 1 pp. 1-6, 1989.
Blessing Gerrit
Hamacher Kurt
Dubno Herbert
Forschungszentrum Jolich GmbH
Phasge Arun S,.
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