This phenomenon is known as Natural Isotopic Fractionation ( see Figure 3 ).
2.
Isotopic fractionation in the hydrologic cycle for more details]
3.
The amount of isotopic fractionation in an exchange reaction can be expressed as a fractionation factor:
4.
At each step of the SNIF-NMR analysis, efforts should be made to avoid parasite isotopic fractionation.
5.
For example, one technique is based on the variation in isotopic fractionation of oxygen by biological systems with temperature.
6.
The analysis of'stable isotopes'is normally concerned with measuring isotopic variations arising from mass-dependent isotopic fractionation in natural systems.
7.
The isotopic fractionation between lipids and methane ( ? l / m ) is 0.94 for fatty acids and 0.79 for isoprenoid lipids.
8.
The isotopic fractionation between lipids and water ( ? l / w ) is 0.95 for fatty acids and 0.85 for isoprenoid lipids.
9.
For plants and algae, the isotopic fractionation between lipids and methane ( ? l / m ) is 0.94 for fatty acids and 0.79 for isoprenoid lipids.
10.
Correcting for isotopic fractionation, as is done for all radiocarbon dates to allow comparison between results from different parts of the biosphere, gives an apparent age of about 440 years for ocean surface water.
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