Determination of residual Kryptofix 2.2.2 levels in [18F]-labeled radiopharmaceuticals for human use

4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (Kryptofix® 2.2.2) is used in the routine preparation of [18F]-labeled tracers employed in positron emission tomography (PET) imaging. Confirming the absence of Kryptofix® in radiopharmaceuticals is a quality control criterion required before they can be released for human use. Analysis of Kryptofix® levels using the iodoplatinate spot-test can be complicated by false-positive results due to nitrogen containing tracers and/or false-negative results caused by added stabilizers. To overcome this issue, we have developed a universal TLC method for the rapid and reliable determination of Kryptofix® levels in the wide range of fluorine-18 radiopharmaceuticals we prepare, including complex multi-component formulations.