Isotope Fractionation

This article is missing information about other fields where isotopic fractionation is observed, e.g., metabolism of natural products, and all methods of analysis thereof, including MS and NMR, all being given balanced treatment. Please expand the article to include this information. Further details may exist on the talk page. (March 2025)

Isotope fractionation describes fractionation processes that affect the relative abundance of isotopes, a phenomenon that occurs (and so advantage is taken of it) in the study geochemistry,^[1] biochemistry,^[2] food science,^[3] and other fields. Normally, the focus is on stable isotopes of the same element. Isotopic fractionation can be measured by isotope analysis, using isotope-ratio mass spectrometry,^[1] nuclear magnetic resonance methods (specialised techniques,^[2][3]) cavity ring-down spectroscopy, etc., to measure ratios of isotopes, important tools to understand geochemical and biological systems, past and present.{{citation needed lead|date=March 2025} l]] processes cause changes in ratios of stable carbon isotopes incorporated into biomass.^{[not verified in body]}

Stable isotopes partitioning between two substances A and B can be expressed by the use of the isotopic fractionation factor (alpha):

α_A-B = R_A/R_B

where R is the ratio of the heavy to light isotope (e.g., ²H/¹H or ¹⁸O/¹⁶O). Values for alpha tend to be very close to 1.^[1][4]

There are four types of isotope fractionation (of which the first two are normally most important): equilibrium fractionation, kinetic fractionation, mass-independent fractionation (or non-mass-dependent fractionation), and transient kinetic isotope fractionation.^{[citation needed]}

Isotope fractionation occurs during a phase transition, when the ratio of light to heavy isotopes in the involved molecules changes. As Carol Kendall of the USGS states in an information page for the USGS Isotope Tracers Project, "water vapor condenses (an equilibrium process), the heavier water isotopes (¹⁸O and ²H) become enriched in the liquid phase while the lighter isotopes (¹⁶O and ¹H) tend toward the vapor phase".^[1]

• Isotope separation

• Ogrinc, N; Kosir, IJ; Spangenberg, JE & Kidric, J (June 2003). "The Application of NMR and MS Methods for Detection of Adulteration of Wine, Fruit Juices, and Olive Oil. A Review.". Anal. Bioanal. Chem. 376 (4): 424–430. doi:10.1007/s00216-003-1804-6. PMID 12819845. 
• Faure G., Mensing T.M. (2004), "Isotopes: Principles and Applications", (John Wiley).^{[full citation needed]}
• Hoefs J. (2004), "Stable Isotope Geochemistry", (Springer Verlag).^{[full citation needed]}
• Sharp Z. (2006), "Principles of Stable Isotope Geochemistry", (Prentice Hall).^{[full citation needed]}
• Akoka, Serge; Remaud, Gérald (October–December 2020). "NMR-Based Isotopic and Isotopomic Analysis". Progress in Nuclear Magnetic Resonance Spectroscopy 120-121: 1–24. doi:10.1016/j.pnmrs.2020.07.001. PMID 33198965. Bibcode: 2020PNMRS.120....1A. https://www.sciencedirect.com/science/article/abs/pii/S0079656520300224. Retrieved 2024-02-11. 

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