An alternative to the reference method for testing the radiochemical purity of Tc-99(m)-tetrofosmin

The recommended method for controlling the radiochemical purity (RCP) of Tc -99(m)-labelled tetrofosmin is thin-layer chromatography (TLC) with silica gel as the stationary phase and acetone:dichloromethane (35:65, v/v) as the mobile phase. However, this test is time-consuming and uses a toxic substa nce. We propose an alternative method to control RCP, based on a solid-phas e extraction method (SPE) using a Sep Pak(R) C18 cartridge. We used both me thods to analyse 35 samples and to determine the percentages of colloid, ra diopharmaceutical and free Tc-99(m)-pertechnerate. Normal labelling process es were modified to obtain a wide range of values. The range of RCP values obtained was 63.4-96.5% (median = 93.8%) by the standard TLC method and 70. 1-96.4% (median = 94.1%) by the SPE method. A significant difference was ob served only for the percentage of free Tc-99(m)-pertechnetate (P < 0.05). T he agreement between the two methods, using 90% RCP as the limit, gave a ka ppa index = +1 (P < 0.001), indicating total agreement between them. The pr oposed method is useful to control RCP because it yields results that are i n good agreement with those of the standard method, and because it is safer and less time-consuming. ((C) 2000 Lippincott Williams & Wilkins).