Absolute dating radiocarbon dating. The development of accelerator mass spectrometry (AMS) dating, which allows a date to be obtained from a very small sample, has been very useful in this regard. Other radiometric dating techniques are available for earlier periods. One of the most widely used is potassium–argon dating (K–Ar dating). Potassium-40 is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years, far longer than that of carbon-14, allowing much older samples to be dated. Potassium is common in rocks and minerals, allowing many samples of geochronological or archeological interest to be dated. Argon,
Kinetic isotope effect depends on the natural abundance of carbon is the slight variation in natural C abundance itself. Such variations arise because the starting materials used in the reaction are themselves products of some other reactions that have kinetic isotope effects and corresponding isotopic enrichments in the products. To compensate for this error when NMR spectroscopy is used to determine the kinetic isotope effect, the following guidelines have been proposed: If these as well as some other precautions listed by Jankowski are followed, kinetic isotope effects with precisions of three decimal places can be achieved. Interpretation of carbon isotope effects are usually