Stable isotope determinations
The atoms of an element can have different amount of neutral particles, neutrons, in their cores. Atoms with different amount of neutrons are called isotopes and non-radioactive isotopes are called stable isotopes. Even though different isotopes have similar chemical properties, small difference in mass between the atoms can cause different behaviour in physical processes and chemical reactions. As a result of this the original isotopic composition can change. The changes are usualle very small and they are measured using Isotope Ratio Mass Spectrometer (IRMS).
The change in the isotopic ratio can indicate how the compound or material was formed or what were the conditions, such as temperature. Due to this, the stable isotope ratios are commonly used when determining things like origin of substances or process chains related to them and they are also widely used in environment or atmospheric research, genuinity and origin research and industrial applications, such as food and beverage industry.
The Laboratory of Chronology has three mass spectrometres available by which the isotopic ratios of hydrogen, carbon, nitrogen or oxygen are determined (2H/1H, 13C/12C, 15N/14N ja 18O/16O). The isotopic ratio is measured in relation to a certified standard and result given as a difference to this standards as permilles (δ2H, δ13C, δ15N ja δ18O). Currently, the Laboratory's main stable isotope projects deal with tree-ring δ13C as a proxy for past climate, and δ13C & δ15N in bones and teeth as tools in reconstructing ancient subsistence patterns and living environments of humans and animals.