Radioactive tracer such as a cell or tissue, or as a flow tracer to track fluid flow. Radioactive tracers are also used to determine the location of fractures created by hydraulic fracturing in natural gas production. Radioactive tracers form the basis of a variety of imaging systems, such as, PET scans, SPECT scans and technetium scans. Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. Isotopes of a chemical element differ only in the mass number. For example, the isotopes of hydrogen can be written as H, H and H, with the mass number at top left. When the
Hydrogen isotope biogeochemistry this, NMR experiments involved constructing massive projects, locating large magnets, and hand wiring miles of copper coil. Proton NMR remained the most popular technique throughout advancements in following decades, but deuterium and tritium were used in other flavors of NMR spectroscopy. Deuterium has a different magnetic moment and spin than protium, but generally a much smaller signal. Historically, deuterium NMR is a poor alternative to proton NMR, but has been used to study the behavior of lipids on membranes. Recently, a variation of deuterium NMR called H-SNIF has shown potential for understating position specific isotope compositions and comprehending biosynthetic pathways.