Chemistry of inorganic compounds – Treating mixture to obtain metal containing compound – Radioactive metal
Reexamination Certificate
2000-04-14
2001-10-30
Bos, Steven (Department: 1754)
Chemistry of inorganic compounds
Treating mixture to obtain metal containing compound
Radioactive metal
Reexamination Certificate
active
06309614
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a new process of separating and purifying multi-curie quantities of yttrium-90 from strontium-90 and other trace elements and impurities while minimizing loss of strontium and amount of waste generated.
BACKGROUND OF THE INVENTION
Although the possibility of treating rheumatoid arthritis, other inflamed joints, and cancer with yttrium-90 (
90
39
Y) is well known, a cost effective way to separate
90
Y of sufficient purify that minimizes loss of radioactive Sr and does not generate a large waste stream is still needed.
90
Y results from the decay of strontium-90 and
90
Y decays to stable
90
Zr according to the following scheme:
38
90
Sr
→
29
Years
39
90
Y
+
B
-
(
0.54
MeV
)
;
39
90
Y
→
64.0
hours
40
90
Zr
+
B
-
(
2.28
MeV
)
90
Y has a relatively short half-life (64.0 h) and maximum beta energy (2.28 MeV) which makes it suitable for a variety of therapeutic uses such as radiolabeling antibodies for tumor therapy or treating liver malignancies.
Although it is known that
90
Y is suitable for immuno radiotherapy, scientists and doctors have encountered numerous difficulties using
90
Y for medical treatments because of the absence of a cost effective way to separate
90
Y of sufficient purity while minimizing loss of radioactive Sr without generating a large waste stream. The following non-exclusive non-exhaustive list of difficulties in separating and purifying
90
Y have limited the application of
90
Y for medical treatment. Although the half-life and decay scheme of
90
Y is appropriate for various radio therapy applications,
90
Y must be capable of being produced in sufficient multi-curie quantities. Furthermore, before
90
Y can be safely used in clinical applications,
90
Y must be essentially free of
90
Sr and any other trace elements.
90
Y must be free of
90
Sr by at least a factor of 10
7
because
90
Sr can suppress bone marrow production.
90
Y must also be free from any trace elements, such as Ca, Cu, Fe, Zn, and Zr, and other impurities because trace elements could interfere with the radio labeling process by competing with
90
Y for binding sites. All of these difficulties must be overcome in a cost effective manner while minimizing loss of valuable radioactive Sr without generating large amounts of waste.
In the past,
90
Y has been separated from
90
Sr by solvent extraction, ion-exchange, precipitation, and various forms of chromatography, all of which fail to separate
90
Y of sufficient quantity and purity in a cost effective manner that minimizes loss of radioactive Sr and does not generate a large waste stream. Numerous procedures use a cation exchange resin (e.g. Dowex 50) to retain
90
Sr, while the
90
Y is eluted with an aqueous solution such as lactate, acetate, citrate, oxalate, or EDTA. Several of these procedures have been proposed as the basis for a
90
Y generator system.
U.S. Pat. No. 5,100,585, and U.S. Pat. No. 5,344,623 describe processes for recovering strontium and technetium from acidic feed solutions containing other fission products.
Another process for separating
90
Y from
90
Sr involves extracting
90
Y from a dilute acid solution of
90
Sr/
90
Y using bis 2-ethylhexyl phosphoric acid in dodecane. This procedure has the disadvantages of having a limited generator lifespan and accumulating radiolytic by-products in the
90
Sr stock. This process also has the disadvantage of requiring repeated stripping of the initial extractant solution to reduce trace impurities and repeated washing of stock solution to destroy dissolved organic phosphates.
Kanapilly and Newton (1971) have described a process for separating multi-curie quantities of
90
Y from
90
Sr by precipitating
90
Y as a phosphate. This process, however, requires adding nonradioactive yttrium as a carrier, yielding
90
Y which are obviously not carrier free and hence unsuitable for site specific binding. This and other prior art teach the addition of only nonradioactive yttrium. This and other prior art do not teach the addition of nonradioactive strontium. In fact, the prior art teaches away from adding nonradioactive strontium.
U.S. Pat. No. 5,368,736 describes a process for isolating
90
Y from a stock solution of
90
Sr. The
90
Sr solution is stored for a sufficient period of time to allow
90
Y ingrowth to occur. This process teaches the use of a series of Sr selective columns at the initial stages of the process. A major disadvantage is that
90
Sr must be stripped off from each of the strontium-selective extraction chromatographic column because
90
Sr is very valuable and it must be recycled to allow for new
90
Y growth.
Unfortunately, all the various methods mentioned above suffer from one or more of the following disadvantages. The first disadvantage of these methods is that the concentration of trace elements is too high and the trace elements thereby compete with
90
Y for binding sites, resulting in a decrease in
90
Y labeling. Thus, it is necessary to either remove trace elements and other impurities prior to antibody labeling or carry out postlabeling purification. The second disadvantage is that ion-exchange resins gradually lose capacity due to radiation damage. As a result, ion-exchange is considered suitable only for purifying and separating subcurie quantities of
90
Y, which is less than the multi quantities of
90
Y needed for clinical applications. The third disadvantage is that separating
90
Y in acceptable purity and quantity while minimizing
90
Sr breakthrough often requires using a series of long ion-exchange columns and impractically large volumes of eluent. A need still exists for a cost effective process of separating
90
Y of sufficient quality and quantity without a series of
90
Sr selective extraction chromatographic columns while minimizing loss of
90
Sr and without generating large amounts of waste and using large volumes of eluent.
SUMMARY OF THE INVENTION
This invention relates to a new process for separating and purifying multi-curie quantities
90
Y of sufficient chemical and radiochemical purity suitable for use in medical applications without a series of
90
Sr selective extraction chromatographic columns while minimizing loss of radioactive
90
Sr parent and waste stream.
It is an object of the invention to separate
90
Y from Sr by a highly selective and efficient Sr precipitation procedure and using Y selective resins and no Sr selective resins. Another object of this invention is to provide a process for separating
90
Y from Sr where
90
Sr activity in
90
Y is reduced by >10
7
. It is a further object of the invention to provide a process for separating
90
Y with an overall recovery of
90
Y>95%. Furthermore, another object of the invention is to provide a process for separating
90
Y with an overall recovery of
90
Sr>99.9% and improved purity with each processing run. Furthermore, another object of the invention is to provide a rapid process for separating
90
Y such that waste generation and radiation damage is minimum.
REFERENCES:
patent: 4835107 (1989-05-01), Horwitz et al.
patent: 5100585 (1992-03-01), Horwitz et al.
patent: 5110474 (1992-05-01), Horwitz et al.
patent: 5154897 (1992-10-01), Ehrhardt et al.
patent: 5225173 (1993-07-01), Wai
patent: 5344623 (1994-09-01), Horwitz et al.
patent: 5368736 (1994-11-01), Horwitz et al.
patent: 5494647 (1996-02-01), Huntley
patent: 5508011 (1996-04-01), Lo et al.
patent: 5512256 (1996-04-01), Bray et al.
patent: 5902566 (1999-05-01), Chinol et al.
patent: 60-097300 (1985-05-01), None
patent: 753037 (1983-09-01), None
patent: 93/23854 (1993-11-01), None
Hines John J.
Horwitz E. Philip
Bos Steven
Mayer Brown & Platt
PG Research Foundation, Inc.
LandOfFree
Method for isolating and purifying 90Y From 90strontium in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for isolating and purifying 90Y From 90strontium in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for isolating and purifying 90Y From 90strontium in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2569728