Radionuclides can be made by nuclear conversion processes in a cyclotron, for example by reirradiating a suitable target with protons. An exact description of a method of separating carrier-free radionuclides from a target liquid is known, for example, from German patent DE 195 00 428.
From German patent document DE 195 00 428 a device is also known (a flow cell) for the separation of carrier-free radionuclides from a target liquid, which is comprised substantially of a cylinder of a carbon glass (Sigradur®) and an axial platinum cannula through which a cylindrical vessel can be filled or emptied through which the inert gas can be fed into the chamber. The system is fixed by means of a plastic support and is sealed. At the lower end a flat funnel is worked which opens into the duct carrying off the water. In the head of the support, there is a gas feed line as well as an opening through which the gas can be discharge. The cylinder of carbon glass (Sigradur®) and the platinum cannula are connected to a direct current source and can be switched to serve either as the cathode or anode. For the recovery of the desired radionuclide, for example, (18F) fluoride from (18O)H2O, the flow cell is filled with (18F) fluoride containing target water. The (18F) fluoride is indirectly deposited on the surface of the cylinder and the (18O) water is transported out of the latter. The height of the zone at which the (18F) fluoride is indirectly fixed is identical with the level of the (18O) water in the cell.
In order that the radio isotope fixed on the surface can be completely transferred to another liquid phase by reversal of the polarity of the electric filled, it is necessary to match the level in the cell to which the latter was filled with the (18O) water. For the subsequent (18F) fluoridation, therefore, a reaction volume must be provided which corresponds to that of the target water. Thus it is necessary to match the quantity of the educt so that it corresponds at the optimal educt concentration to this volume (for example 1.3 ml). Because of the very small quantities or proportions of these products (picomoles to nanomoles) with respect to the proportion of unoriented educt (μmol), difficulties in separation occur during purification and especially during chromatographic purefaction. Since the mass of the educt significantly exceed the mass of the product, an HPL-chromatographic separation can only run with poor resolution.