Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

12.1.1.4. Acid vapour trap and radioactive waste collection
Because of the long half-life of 90 Sr, acid vapour and other radioactive
wastes were collected in a closed system after decreasing their volume. Acid
vapour from the evaporation flask was evacuated using polyvinyl chloride tubing
with an air jet pump (activated by compressed air) and trapped in an acid scrubber
unit kept outside the fume hood. The unit had continuous circulating water from
a storage tank and the drain returned to the tank. Other radioactive wastes in the
process box were then washed and kept in a 20 L storage vessel under the fume
hood, with the drainage port located on the box floor.
12.1.2. Strontium-90/yttrium-90 extraction generator
Three columns of strontium resin (Eichrom Technologies) were connected
in tandem. A concentration of 3M HNO 3 was used as the eluent for 90 Y extraction
and 0.05M HNO 3 for 90 Sr recovery. The flow rate of the peristaltic pump was set
at 0.5 mL/min and 90 Y was collected for 30 mL in an evaporating flask, which
was subsequently heated to dryness. The residue containing the 90 Y product
was dissolved with 0.05M HCl. Strontium-90 adsorbed in the first and second
columns was recovered with 0.05M HNO 3 (30 mL each) and collected in
another evaporation flask, which was then heated to almost dryness for the next
cycle. Strontium-90 was used at the tracer level (300–400 µCi) and the low
level (6–8 mCi) to monitor the elution characteristics and for evaluation of the
generator performance, respectively.
12.1.3. Strontium-90/yttrium-90 ion exchange generator
Two ion exchange resin columns (Dowex 50WX8, 100–200 mesh, H + form)
were connected in tandem. Strontium-90 was dissolved in 0.003M EDTA, pH4.5,
and loaded onto the first column. The generator was eluted with 40 mL of this
buffer into an evaporating flask to enable collection of 90 Y in the form of the
90 Y EDTA complex. The eluate was subsequently digested with concentrated
H 2 SO 4 /concentrated HNO 3 by heating (300°C) to dryness. This 90 Y was
preconditioned for purification by redissolving it in 0.05M HCl. Strontium-90
from the first column was recovered by washing with 20 mL of 2M HNO 3 and
20 mL of 4M HCl and subsequently collected in another evaporating flask. This
was then heated to almost dryness for the next cycle. The amount of 90 Sr activity
loaded was the same as that used in the 90 Sr/ 90 Y extraction generator.
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