Studies on an extractor-generator for use in routine production of Tc-99m at PAEC

This report dwells on the author's preliminary studies on the use of a locally fabricated compact liquid extractor. The extractor is a modification of the apparatus described by R.J. Baker (Int. J. App. Rad. and Isot., 22: 483-485, 1971). It consists of a Pyrex glass column (70 mm x 25 mm) of volume 8 ml with a capillary tube attached to the bottom and an overflow at the top. The narrowed top provides for settling of MEK and the widened bottom, for stirring by a magnetic stirrer. The column is housed in a cylindrical lead shield. A hole was made at the bottom of the cylinder to permit stirring and to stabilize the unit on the stir plate especially during stirring. The irradiated target (1-3g) is dissolved in 10 ml of strong NaOH solution (5-10N) and 8 ml of the solution are introduced into the extractor through the capillary tube. The solvent, MEK is allowed to drop through the capillary tube at a rate of about 1 ml and the overflow containing the 99mTc is collected into a beaker. The solvent is evaporated off and the residue is taken up with the desired volume of isotonic saline solution. Yields and extraction efficiencies were determined by comparing the 99mTc activity present in the final and target solutions after equilibrium has been attained. The results suggest that the extraction efficiency was dependent on the purity of the MEK used. In a series of extractions, the 99mTc yield continuously decreased from 95% to as low as 30% of the extractable 99mTc. Freshly distilled MEK was used each time in other experiments where higher yields were consequently obtained. Tests for radiochemical purity showed that the Tc was present in pertechnetate form, Tc (VII). No 99Mo, that is higher than the permissible 0.1% was detected by a paper chromatographic test, half-life determinations, gamma ray spectrometry and low energy gamma filtration by lead absorbers