Non-ITLC SG miniaturized chromatography procedures to evaluate hydrolyzed reduced Tc-99m in specific Tc-99m radiopharmaceuticals

Objectives The current miniaturized chromatography system (MCS) to evaluate hydrolyzed reduced Tc-99m (Tc-HR) in Tc-99m Disofenin, Pentetate and Medronate consists of ITLC-SG chromatography paper. Since this product has been discontinued, alternative MCS paper were evaluated.

Methods A number of MCS systems were evaluated to determine the Tc-HR fraction in specific radiopharmaceuticals (RRX) including Medronate, Pentetate and Disofenin. The optimal MCS consisted of SA impregnated paper with distilled water (SA-MCS). For Tc-99m Medronate, the effect of pre-spotting with unlabeled Medronate on this MCS was further evaluated. Activity distribution of the specific RRX was obtained with SA-MCS. In addition, the Tc-HR fraction in specific RRX was assessed and compared to the standard MCS consisting of ITLC-SG with distilled water MCS (SG-MCS). For each specific RRX and MCS, ten replicate samples were obtained and the data statistically summarized by calculating mean percent Tc-HR and standard deviation.

Results Using the SA paper with distilled water MCS, maximal separation between Tc-HR and the specific radiopharmaceutical was achieved for all Tc-99m RRX evaluated with Rf values of 0.0 and 0.9-1.0, respectively. The mean Tc-HR percent in Tc-99m-Disofenin (N=10) for the SG-MCS and the SA-MCS was 0.8% and 1.3%, respectively. The mean Tc-HR percent in Tc-99m-Pentetate (N=10) for the SG-MCS and the SA-MCS was 0.1% and 0.1%, respectively. The mean Tc-HR percent in Tc-99m-Medronate (N=10) for the SG-MCS, the SA-MCS and SA-MCS with pre-spotting was 0.3%, 2.4% and 0.4%, respectively. The standard deviation in all RRX tested was less than 0.009%.

Conclusions A MCS consisting of SA impregnated chromatography paper with distilled water was utilized to evaluate Tc-HR in specific Tc-99m radiopharmaceuticals. Maximum separation in radiochemical species was achieved and comparable results in accuracy were noted when compared to conventional SG-MCS