isotopically

Isotopically is an adverb related to isotopes, the variants of a chemical element that differ in neutron number and thus in atomic mass while typically sharing chemical properties. In practice, isotopically refers to the isotopic composition of a sample, a process, or an analysis, including the use of isotopes as tracers or labels. A material can be isotopically characterized by the ratios of its isotopes, often expressed relative to a standard in delta notation (for example, δ13C or δ18O).

Isotopic analysis is performed mainly by mass spectrometry. Techniques such as isotope ratio mass spectrometry (IRMS) measure precise isotope ratios, while thermal ionization mass spectrometry (TIMS) and inductively coupled plasma mass spectrometry (ICP-MS) extend capabilities to a wide range of elements. Secondary ion mass spectrometry (SIMS) provides spatially resolved isotope information on solid samples. These measurements enable comparisons of natural abundance variations, dietary or ecological sources, and physical or chemical processes that fractionate isotopes during reactions or phase changes.

Applications of isotopic information span geoscience, environmental science, biology, and medicine. Stable isotopes (such as 2H, 13C, 18O) are widely used because they persist over time, in contrast to radioactive isotopes used for dating or tracing turnover. Isotopically enriched or labeled compounds, including 13C- or 15N-labeled substrates, serve as tracers in metabolic studies and diagnostic research. Isotopic signatures aid paleoclimate reconstructions, groundwater source identification, food web studies, forensic science, and the tracking of pollutants or carbon and nitrogen cycles.

Overall, isotopically describes data, materials, or methods defined by their isotopic composition or labeling, a central concept in modern analytical and Earth-science disciplines.