A quality control procedure for 99mTc-IDA complexes based on the use of C18 Sep-pak cartridges is developed and the validation of the procedure presented. C18 Sep-pak cartridges are pretreated by washing with 95% ethanol followed by 10(-3) N hydrochloric acid. A small amount of the 99mTc-IDA complex is applied, washed with 10(-3) N hydrochloric acid and eluted with 95% ethanol. The radiochemical purity values obtained for 99mTc-mebrofenin and 99mTc-disofenin using this Sep-pak procedure are comparable to those obtained using the standard two strip (ITLC-SG/100% methanol, ITLC-SA/20% saline) procedure.