Alternative Method of Radiochemical Purity Testing for Technetium-99m Tetrofosmin

Tc-99m tetrofosmin is a radiopharmaceutical preparation used in nuclear medicine. Radiochemical purity as main parameter of quality should be more than 90%, and was determined using thin layer chromatography with ITLC-SG as stationary phase and mixture of acetone and dichloromethane as mobile phase. Since ITLC-SG is expensive and the solvent used is rather noxious, an alternative method is expected to replace it for routine QC use. Besides, the radiolabeling capability of Tc-99m in low radioactivity is expected to reduce the utilization of Tc-99m in QC of kits manufacturing. Experiment using SepPak C18 column and TLC system with TLC-SG and ITLC-SG were carried out, then the results were compared. Radiochemical purity measurement using TLC-SG and ITLC-SG showed 99.49 ± 0.78% and 96.17 ± 2.37% respectively with the peaks observed at Rf 0.0 and ~ 0.5 respectively, whereas that using SepPak C-18 showed RCP of 98.51 ± 0.78%. Various radioactivity of Tc-99m from 2 to 100 mCi have been used to label tetrofosmin kits and the radiolabeling quality were almost the same. It can be concluded that SepPak C18 as well as TLC method using TLC-SG can be used as alternative methods for radiochemical purity measurement of Tc-99m tetrofosmin, and low radioactivity of Tc-99m is sufficient to label tetrofosmin with high radiochemical purity.