Isotope fractionation describes processes that affect the relative abundance of isotopes, often used in
isotope geochemistry. Normally, the focus is on
stable isotopes of the same element. Isotopic fractionation in the natural environment can be measured by
isotope analysis, using
isotope-ratio mass spectrometry, to separate different element isotopes on the basis of their mass-to-charge ratio, an important tool to understand natural systems. For example, in
biochemistry processes cause a fluctuation in the amount of
carbon isotope ratios incorporated into a biological being. The difference between the true amount of carbon and the amount in the plant is known as isotope fractionation.