Our basic
analysis includes measuring Carbon and
Nitrogen stable isotope ratios, %C and %N.
Stable Isotope analysis can be used for:
Dietary reconstruction
Trace flows of energy and nutrients
Patterns of migration
Dispersal
Habitat use
Weaning and fasting
How a sample is analyzed: Samples are placed in clean metal capsules
and loaded into an automatic sampler. They are then dropped into a furnace
held at 1100C where they are combusted in the presence of added oxygen. The
combusted gases are then swept in a helium stream over a combustion catalyst
(chromium dioxide), silvered cobalt and quartz wool to remove sulfur and
halides. The remaining gases (nitrogen, carbon dioxide, oxygen and water)
are then swept through a reduction stage of pure copper wires held at 800C.
This step will remove any oxygen. Water is removed by a magnesium
perchlorate trap. Nitrogen and carbon dioxide are separated by packed
column gas chromatograph held at an isothermal temperature. The resultant
chromatographic peak enters the ion source of the mass spectrometer where it
is ionized and accelerated. Gas species of different mass are separated in a
magnetic field then simultaneously measured on a Faraday cup universal
collector array. For N2, masses 28, 29, and 30 are collected and for CO2,
masses 44, 45, and 46.