To simulate 90Y-Zevalin thin-layer chromatograms representing a range of radiochemical purities, to compare the radiochemical purities obtained with five techniques used to quantify 90Y on the plates and to measure the reproducibility of the five techniques at the minimum acceptable radiochemical purity of 95%.
Yttrium-90 solutions were pipetted onto the origin and solvent front lines of thin-layer chromatography (TLC) plates to simulate radiochemical purities of 90%, 92%, 94%, 95%, 96%, 98% and 100%. Each plate was analysed using three TLC scanners (Bioscan AR2000, Bioscan Mini-scan and an instrument constructed in-house) and two cut-and-count techniques: one using a sodium iodide well detector and the other a liquid scintillation counter. The reproducibility of each technique was measured by analysing the 95% plate 10 times.
The radiochemical purities measured by the five techniques agreed well. The means of the seven results obtained with each agreed within 0.7%. The reproducibility of each technique was excellent. The coefficient of variation for 10 measurements was ≤0.3%. The signal to background ratios were satisfactory, ranging from 24 to 2.1×105.
Each technique is suitable for analysing 90Y-Zevalin TLC plates.
Radiopharmacy, The Royal Infirmary of Edinburgh, Edinburgh, UK
Correspondence to Dr Alistair M. Millar, Department of Pharmacy, The Royal Infirmary of Edinburgh, Little France Crescent, Edinburgh EH16 4SA, UK
Tel: +44 131 242 2929; fax: +44 131 242 2931
Received 8 July 2004 Revised 6 October 2004 Accepted 18 October 2004