OPA reagent (#5061-3335) was obtained from Agilent. Analytical and semi-preparative RP-HPLC were performed with an Agilent 1200 HPLC system equipped with a 1200 Series Diode Array Detector and a GABI Star NaI(Tl) scintillation detector (energy window 400-700 keV) (Raytest). Isolated RCY refers to the activity of the pure radiotracer isolated after HPLC divided by the initial activity of [ 18 F]fluoride in [ 18 O]H 2 O used for the labelling. RCY are given decay corrected. RCP refers to the proportion of the total radioactivity in the sample which is present as the desired radiotracer, as measured by radio-HPLC .