Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

From each fraction, a ~1 g aliquot was taken by weight into 20 mL LSC
vials. Volumes of 1.5 mL deionized water and 10 mL of Ultima Gold AB liquid
scintillator were added into each vial. Measurements were carried out using a
Wallac 1411 spectrometer. The spectra of these three fractions are shown in
Fig. 9.1.
Fraction 1 contained the total 90 Sr activity with a few counts of 90 Y owing
to the decay of 90 Sr during collection of the 90 Sr fraction and measurement.
Fractions 2 and 3 did not contain any activity. The spectra showed only
background counts.
The relationship between the added and measured 90 Sr activity is shown
in Fig. 9.2. The intersection point of the straight line with the ordinate axis
determines the 90 Sr activity in 90 Y used for validation. The determination limit
of 90 Sr in 230 MBq of 90 Y was equal to 3.5 × 10 –6 % for a measurement time of
200 s. This limit can be lowered to 1×10 –6 % for a 3600 s measurement time.
9.2. COMPARISON OF METHODS FOR
CHROMATOGRAPHIC SEPARATION OF DMSA COMPLEXES
WITH 99m Tc AND 188 Re IN (III) AND (V) OXIDATION STATES;
IMPLICATIONS OF PRODUCT DEVELOPMENT
(IN COLLABORATION WITH VINČA INSTITUTE OF
NUCLEAR SCIENCES, BELGRADE, SERBIA)
The reliable method for determination of RCP is key to the success of
further radiopharmaceutical development. This is especially relevant when more
than one type of radiometal ligand complex can be formed during labelling. In the
case of DMSA complexes with 99m Tc or 188 Re, depending on the pH, the metal can
occur at +3 or +5 oxidation states [9.6]. Although, the European Pharmacopoeia
monograph [9.7] describes RCP tests for 99m Tc(III) DMSA based on ITLC SG
chromatography, this method is not specific for distinct forms of complex and
allows only determination of free 99m Tc pertechnetate. Both 99m Tc(III) DMSA
and 99m Tc(V) DMSA are retained at the origin similar to colloidal residues of
99m Tc. The method proposed by Westera et al. [9.8] utilizing SG coated plates
and BuOH:H 2 O:acetic acid (3:3:2) allows separation of 99m Tc(III) DMSA from
99m Tc(V) DMSA complexes in a separation process lasting 2 h, but still does not
allow determination of technetium tin colloid (BuOH = butanol).
The goal of this work was to evaluate possibilities for optimization
of chromatographic systems leading to a one step analytical method for
determination of the RCP of DMSA complexes with 99m Tc or 188 Re.
137