4.4.1. Biodistribution of [18F]6

14.3 <sup>±</sup> 0.5 MBq (*n* = 12) (25.4 <sup>±</sup> 1.4 <sup>μ</sup>g, 44.2 <sup>±</sup> 2.4 nmol) of 96.2% pure [18F]6 was injected into the tail vein of healthy female CD-1 mice (*n* = 3 per time-point), to evaluate the biodistribution and stability of the tracer in vivo. The mice were euthanized at selected time-points (*t* = 5, 60, 120, and 240 min) and the tissues were collected and measured with a gamma counter, as described above. For metabolite studies, blood from a cardiac puncture was collected into an Eppendorf tube containing 2 μL of 1% heparin solution in 0.9% NaCl (aq.) and centrifuged at 1000 *g*, for 10 min, to separate the plasma from the blood cells. Cold acetonitrile (twice the volume of separated plasma) was added into the plasma and centrifuged (at 10 000 g for 5 min) to precipitate the proteins. A small sample (4 μL) was applied onto a silica TLC and analyzed with digital autoradiography.
