Evaluation of hydrolyzed impurities in radiochemical analysis and biological distribution of 99mTc-ECD

Abstract

99mTc-L,L-ethylcysteinate dimer (99mTc-ECD) is used for investigations of cerebralperfusionandthehydrolyzedform(99mTcO-ECD)isanimpuritythatcan beaninterferenceinthequalityoftheimage.Theaimofthisstudywastodevelopa method by high-performance liquid chromatography (HPLC) for determination of 99mTcO-ECD in 99mTc-ECD preparation and to study both biodistribution in mice.TheHPLCsystemwasLC20ATProminencemodelandaShim-PackVPODScolumn(250×4.6mmi.d.,5μm).99mTc-ECDwaspreparedbyadding1ml of 0.9% NaCl, 1 ml of phosphate buffer (pH 7.5) and 1 ml of Na99mTcO4.The radioactiveconcentrationwas55.5MBqml−1.20μLsamplevolumewasinjected ina1.0mlmin−1flowrate.Alineargradientwasperformedwithethanoland12.5 mmol L−1 phosphate buffer (pH 2.5). 99mTc-ECD (555 MBq L−1) was intravenously injected in the mice tail vein in a Swiss mice (15–20gweight). After 10min,theanimalsweresacrificedand theinjecteddose (i.d.) in brainwas evaluated. The retention time of 99mTcO-ECD and 99mTc-ECD was 14.65 and 17.38 min, respectively. Biodistribution results showed normal brain uptake of 0.92%i.d. for 99mTc-ECD. Higher 99mTcO-ECD reducedsignificantly the brain uptake in biodistribution in mice and HPLC method showed to be an important tool for the separation and quantification of 99mTc-ECD and 99mTcO-ECD.