Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

6.1.3. Recovery of doped 85/89 Sr 2+ determined by EPC
To confirm the efficiency of separation of 90 Sr from 90 Y using the EPC
method, a doping experiment was carried out. Known counts of 85/89 Sr(NO 3 ) 2
solution were doped in 90 Y solution. EPC was carried out with a mixture of
5 µL of 85/89 Sr(NO 3 ) 2 and 5 µL of 90 Y acetate, as well as 5 µL of 85/89 Sr(NO 3 ) 2
as control. The solvent front corresponding to 85/89 Sr counts was counted
in a NaI(Tl) counter, and the counts corresponding to 85/89 Sr (in the solvent
front) were compared to counts of 85/89 Sr(NO 3 ) 2 to determine the efficiency
of separation by the EPC system. Figure 6.3(a) shows the EPC pattern of
90 Y + 85/89 Sr, while Fig. 6.3(b) is the EPC pattern of 85/89 Sr only. It was observed
that almost all the 85/89 Sr activity could be recovered at the solvent front of the
extraction chromatography paper.
(a)
(b)
FIG. 6.3. EPC pattern of (a) 90 Y + 85/89 Sr and (b) 85/89 Sr only.
6.1.4. Analysis of long decayed 90 Y samples using the EPC technique
The 90 YCl 3 or 90 Y acetate obtained from 90 Sr/ 90 Y generator systems were
assigned batch numbers, and the samples were allowed to decay for more than
two months from the date of elution from the generator. After two months, EPC
was carried out for all samples. At the end of 60 days, 90 Y would have decayed
by ~22.5 half-lives, by which time, it is expected that 99.99999% of the 90 Y has
decayed and if any 90 Sr were present, it would still be present. At this juncture,
the 90 Sr present would be in secular equilibrium with its in grown 90 Y, and the
90 Sr: 90 Y ratio would be equal to 1. The counts at the origin (R f = 0) correspond
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