STABLE ISOTOPE

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Stable isotopes are chemical isotopes that are not radioactive. Stable isotopes of the same element have the same chemical characteristics and therefore behave almost identically. The mass differences, due to a difference in the number of neutrons, result in partial separation of the light from heavy isotopes during chemical reactions (isotope fractionation). For example, the difference in mass between the two stable isotopes of hydrogen, ¹H (1 proton, no neutron, also known as protium) and ²H (1 proton, 1 neutron, also known as deuterium) is almost 100%. Therefore, a significant fractionation will occur.

Commonly analysed stable isotopes include oxygen, carbon, nitrogen, hydrogen and sulfur. These isotope systems have been under investigation for many years as they are relatively simple to measure. Recent advances in mass spectrometry (ie. muliple-collector inductively coupled plasma mass spectrometry) now enable the measurement of heavier stable isotopes, such as iron, copper, zinc, molybdenum, etc.

Stable isotopes have been used in botanical and plant biological investigations for many years, and more and more ecological and biological studies are finding stable isotopes (mostly carbon, nitrogen and oxygen) to be extremely useful. Other workers have used oxygen isotopes to reconstruct historical atmospheric temperatures, making them important tools for climate research.

Stable isotope fractionation

There are three types of isotope fractionation:

• equilibrium fractionation
• kinetic fractionation
• mass-independent fractionation

See also

• isotope table (complete)
• isotope table (divided)
• Isotope geochemistry
• List of stable isotopes