An evaluation of GMCP-SA as a replacement for ITLC-SG when measuring the levels of radiochemical impurities in 99mTc radiopharmaceuticals by thin-layer chromatography

Background: The European Pharmacopoeia and radiopharmaceutical manufacturers specify Instant Thin-Layer Chromatography Silica Gel impregnated glass fibre (ITLC-SG) as the stationary phase for measuring the radiochemical purity (RCP) of most technetium-99m (99mTc) radiopharmaceuticals. During 2008, The Pall Corporation stopped manufacturing ITLC-SG. A replacement is required. Aim: To evaluate Varian's Glass Microfibre Chromatography Paper impregnated with salicic acid (GMCP-SA) as a replacement. Experimental: Samples of six 99mTc radiopharmaceuticals (albumin nanocolloid, colloidal tin, exametazime, medronate, pentetate and succimer) were prepared containing levels of radiochemical impurities between 0 and 10%. Samples were tested using ITLC-SG and GMCP-SA with the mobile phase specified in the pharmacopoeia or by the manufacturer. Analysis was performed by thin-layer radiochromatogram scanning. Results: For measuring the RCP of albumin nanocolloid, colloidal tin, exametazime and succimer, GMCP-SA is a suitable replacement for ITLC-SG. For medronate, GMCP-SA is suitable for measuring colloidal 99mTc impurity despite producing slightly higher values than ITLC-SG, but unsuitable for measuring 99mTc pertechnetate impurity due to significant over-estimation. For pentetate, GMCP-SA is suitable for measuring colloidal 99mTc impurity but gives slightly higher values for 99mTc pertechnetate impurity than ITLC-SG. Conclusion: GMCP-SA is a suitable alternative to ITLC-SG for analysing some 99mTc radiopharmaceuticals but is not a universal replacement. Copyright © 2009 John Wiley & Sons, Ltd.