Extraction Paper Chromatography Technique for the Radionuclidic Purity Evaluation of ~(90)Y for Clinical Use

摘要

Yttrium-90 used for therapy should be of very high radionuclidic (RN) purity (>99.998percent) as the most probable contaminant, strontium-90, is a bone seeker with a maximum permissible body burden of 74 kBq (2 (mu)Ci) only. None of the current known methods of RN purity estimations is adequate to reliably measure the ~(90)Sr RN impurity at such low levels. Our aim was to develop a reliable technique to accurately determine the amount of ~(90)Sr in ~(90)Y used for therapy. This new technique combines chelate-based extraction with paper chromatography using paper impregnated with 2-ethylhexyl, 2-ethylhexylphos-phonic acid (KSM-17), which is a ~(90)Y-specific chelator. A PC strip impregnated with KSM-17 at the point of spotting is used for chromatography. Upon development with normal saline, ~(90)Sr moves to the solvent front leaving ~(90)Y completely chelated and retained at the point of spotting. The activity at the solvent front (~(90)Sr) is quantified by liquid scintillation counting, and the data are compared with the total applied activity to provide the RN purity of the test solution. The method has a sensitivity of >= 74 kBq (2 (mu)Ci) of ~(90)Sr per 37 GBq (1 Ci) of ~(90)Y. This novel, innovative, and simple technique offers a reliable solution to the unanswered problem of estimation of ~(90)Sr content in ~(90)Y used for cancer therapy.