What is a stable isotope?
Stable isotopes are variants of the same element. The differ because they contain a different number of neutrons in their nucleus. Stable isotopes are everywhere and do not emit radioactivity. Most elements in the periodic table have stable isotopes, some have only one (phosphorous) some have many (the element with the highest number of stable isotopes is tin). Isotracer srl deals with environmental isotopes. We like this term, though it does not have a precise definition. Environmental isotopes are those found in biological and hydrological systems. Presently, we focus on hydrogen, carbon, nitrogen and oxygen. Stable isotopes are not consumed nor produced in time scales relevant to environmental studies, therefore their global mean abundance can be assumed to be constant. The chemical behavior of different stable isotopes of the same element is pretty much identical. However, the heavy isotopes are (generally) slower than the light isotopes. This creates local differences in the ratio between isotopes. And this is why we can use them as tracers.
How are stable isotopes measured
Until recently, the most common methods to measure stable isotopes in materials were the isotopic ratio mass spectrometer (IRMS) and the nuclear magnetic resonance (NMR). Today also a third method is getting popular and it is based on laser spectroscopy.