Abstract
We present planar alumina as a solid phase extraction surface for purification steps of on-chip chemical synthesis. Droplet mixing, by electrowetting and resistive heating, induced sufficient surface interaction with alumina to remove [ 18 F]fluoride ion from a droplet. This mechanism was used for purification of [ 18 F]fallypride (a radiolabeled neurotransmitter for studying Alzheimer's disease with positron emission tomography) after it was produced on chip.