Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

(a)
FIG. 10.15. (a) The electrolytic cell and (b) electrolytic separation of H 2 gas
(b)
90 Sr in 90 Y solution for human use was set at 74 kBq (2 mCi), the development of
quality control methods was essential.
The radionuclidic purity of the 90 Y solution was analysed using paper
chromatography and ITLC. Paper chromatography on Whatman No. 1
(18 cm × 2 cm) and ITLC SG strips (14 cm × 1 cm) using 0.9% saline solution
was used for the analyses. In this method, 90 Sr moved to the solvent front,
while 90 Y remained at the origin. The radionuclidic purity was calculated as a
percentage of the total activity spotted.
Comparative results of RCP of 90 Y before and after electrolysis were
obtained using paper chromatography (see Fig. 10.16), wherein two peaks were
observed of 90 Sr and 90 Y at equilibrium (see Fig. 10.16(a)). The absence of a peak
at 10 cm (see Fig. 10.16(b)), which represents free 90 Sr, indicated that separation
of 90 Y from 90 Sr by electrochemical separation was successful.
The quality of separation was determined by measuring the radioactivity of
90 Y solution over time, following the half-life of 90 Y. The decay was followed for
31 d, which is ~11.6 half-lives of 90 Y. The absence of deviation in the lower part
of the curve in Fig. 10.17 confirmed the absence of 90 Sr. The y axis is given as the
logarithm of observed values.
To determine the radionuclide purity of the 90 Y solution, a combination of
solvent extraction and EPC was used. This method is a sensitive and accurate
analytical technique for estimation of the purity of 90 Y. The EPC pattern of
90 Y is shown in Fig. 10.18, wherein 90 Sr moved to the solvent front, while 90 Y
was retained at the point of spotting. Radionuclide purity was calculated as the
percentage of the total activity spotted, estimated by measuring radioactivity in
a dose calibrator. These results revealed only a very low level of 90 Sr impurity
(