| Oxygen-18 | |
|---|---|
| General | |
| Name, symbol | Oxygen-18,18O |
| Neutrons | 10 |
| Protons | 8 |
| Nuclide data | |
| Natural abundance | 0.2% |
Oxygen-18 (18O) is a natural, stable isotope of oxygen and one of the environmental isotopes.
18O is an important precursor for the production of fluorodeoxyglucose (FDG) used in positron emission tomography (PET). Generally, in the radiopharmaceutical industry, enriched water (H218O) is bombarded with hydrogen ions in either a cyclotron or linear accelerator creating fluorine-18. This is then synthesized into FDG and injected into a patient.
In ice cores, mainly Arctic and Antarctic, the ratio O-18/O-16 is used to retrieve the temperatures of the precipitation during different years. The temperature relationship exists because water molecules containing heavy O-18 preferentially freeze before those with O-16. Water molecules are also subject to Rayleigh fractionation as atmospheric water moves from the equator poleward. In the 1950s, Harold Urey performed an experiment in which he mixed both normal water and water with oxygen-18 in a barrel, and then partially froze the barrel's contents. The water with oxygen-18 sunk to the bottom of the barrel and was first to freeze[citation needed].
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