TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: In the radiosynthesis of a radiotracer suitable for use in positron emission tomography (PET), microfabricated device is used. The radiosynthesis involves:(1) pre-treatment of a radioactive reagent or a precursor;(2) synthesis of a radiolabelling agent;(3) mixing and reaction of a radiolabelling agent with a precursor using microfabricated mixing and reaction device to produce a radiolabeled product;(4) chemical modification of a radiolabeled product;(5) analysis of a radiolabeled product using microfabricated analysis device; and/or(6) separation of a radiolabeled product from at least one by-product using microfabricated separation device.Preferred Components: The radiolabelling agent is (11C)methane, (11C)carbon dioxide, (11C)carbon monoxide, (11C)RX, R'(11C)COCl, R'(11C)COOH, R'(11C)CH2OH, R'(11C)COH, R'(11C)COR', (11C)CN-, (11C)CCl4, (11C)phosgene, (11C)urea, (11C)cyanogen bromide, (18F)fluoride or (124I)iodide.R, R' = methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, benzyl, cyclopentylmethyl, cyclohexylmethyl or fluoro- or its halo-analogs;X = halo, mesylate, tosylate, triflate, nonaflate, nitrate, thiol, isocyanate, lithium or aldehyde. EXAMPLE - A glass drying-vessel was prelocated with Kryptofix(2.2.2) (4 mg) and K2CO3 (4.6 mg) dissolved in H2O (200 microg) and acetonitrile (800 microl). To this vessel, the aqueous (18F)fluoride (1 ml) was added and the vessel heated to 120 degrees C with an over flow of nitrogen gas (2 ml/minute). After 10 minutes of heating, acetonitrile (1 ml) was added. Further 2 additions of acetonitrile (1 ml) measures followed at 10 minutes intervals until the fluoride was completely dried and stirred at 80 degrees C (2 minutes). The fluoride/Kryptofix(2.2.2.) residue was reconstituted in acetonitrile (1 ml). For 'on-chip' radiolabelling the dried K+/K 2.2.2/(18F)fluoride in acetonitrile was infused (using precision syringe drives) into one of the two chip inlets while tetraacetylmannose triflate (FDG precursor) solution (10 mg in 500 microl acetonitrile) was infused, at an equal rate into the other. The total flow rate was 5-100 microl/minute and the reaction was carried out at 75 degrees C to give 2-(18F)fluorinated tetracetylated deoxyglucose. Product mixture collected from the chip outlet was analyzed by HPLC, flow rate 2 ml/minute, mobile phase: 80% acetonitrile, 20% water. The product, unhydrolized FDG eluted at about 2 minutes with no other radiochemical fraction evident. The radiochemical yield was 20-49%, n = greater than 10. The acetyl protecting groups were subsequently removed by acid or base hydrolysis by addition of an aqueous solution of hydrochloric acid or sodium hydroxide respectively. Thus two microfabricated devices were operated in series to extend the fluorination step to the deprotection step. 2-(18F)fluorinated tetracetylated deoxyglucose prepared above was fed into one port of a second identical device and aqueous sodium hydroxide was fed into a second port of the device. The solutions were mixed at room temperature to give 2-(18F)fluoro-2-deoxy-D-glucose in 24 % radiochemical yield. This was a continuous flow process, the residence time of the fluid on the combined device network being less than 1 minute. The product obtained was 2-(18F)fluorinated tetraacetylated deoxyglucose (after 3.5 minutes) at 2-3.374 mV, (18F)fluoride (after 5.25 minutes) at 3-5.033 mV and 2-(18F)fluoro-2-deoxy-D-glucose (after 10 minutes) at 4-9.896 mV.