Validation of a cartridge method for the quality control determination of 99Tcm-HMPAO

Full text: The manufacturer's method for assessing the radiochemical purity (RCP) of ±-HMPAO requires the use of three solvent types on two different stationary phases, and is time-consuming (∼ 15 min) in consideration of the short shelf-life (30 min). An impetus to develop a rapid quality control procedure for this product has led to the use of a single strip Whatman 17 chromatography system using ethyl acetate as the developing solvent. This popular Whatman paper system was previously validates against the manufacturer's method. We have developed a new method to successfully determine the % RCP of ±-HMPAO, which employs a disposable, inexpensive and reusable Amprep C-18 cartridge with normal saline as a non-organic mobile phase. The Whatman paper system separates the primary lipophilic 99Tcm-HMPAO complex from 99TcmO-2, 99TcmO4 and secondary 99Tcm-HMPAO complex at the origin. By comparison, the lipophilic portion was retained on the cartridge and the hydrophilic impurities were found in saline eluent with the cartridge method. Whatman 17 paper system results showed 95.1 ± I.7% 99Tcm-HMPAO after 5 min and the cartridge method gave 95.5 ± 1.5% 99Tcm-HMPAO (n = 8) after 3 min. The % 99TcmO2 levels in 99Tcm-HMPAO were insignificant. When a failed kit was assessed for RCP at 2.5 h post-reconstitution, the Whatman paper system and the cartridge method correlated well, resulting in 63.1 ± 2.7% and 62.9±2.1% 99Tcm-HMPAO (n=3) respectively. Although the cartridge method may slightly overestimate the % RCP of 99Tcm-HMPAO, it was found to be simple, rapid and reliable for the quality control analysis of routine 99Tcm-HMPAO preparations