13carbon

Carbon-13 (13C) is a stable isotope of carbon with a mass number of 13. It contains six protons and seven neutrons. In nature, carbon exists primarily as two stable isotopes, 12C and 13C, with 13C making up about 1.1% of natural carbon.

Because it is stable, 13C does not decay and has a long natural lifetime. It is present in all carbon-containing materials, including carbon dioxide, organic matter, and carbonate minerals. It is produced in stars through nuclear fusion and is also formed by cosmogenic processes such as cosmic ray spallation on Earth.

Nuclear properties: 13C has a nuclear spin of 1/2, which gives it a nonzero magnetic moment and makes it observable by 13C nuclear magnetic resonance (NMR) spectroscopy. Its relatively small natural abundance is commonly increased by isotopic labeling for experimental purposes.

Applications: Isotopic labeling with 13C is widely used in biochemistry and metabolomics to trace carbon flow in organisms, and in chemistry to track reaction mechanisms. 13C NMR is a standard analytical method that provides information about molecular structure and dynamics. The 13C/12C ratio is also used in geochemistry and archaeology to study carbon sources and the carbon cycle, using delta-13C notation (δ13C) relative to a standard such as VPDB.

Enrichment and measurement: Laboratories obtain 13C-enriched compounds by synthesis; measurement is performed by isotope ratio mass spectrometry or NMR spectroscopy. 13C is non-radioactive and generally regarded as safe for routine laboratory handling.