Rights: The University of Waikato Published 21 June 2007 Download

Dr Katja Riedel of NIWA explains what isotopes are and how they are being identified and measured from the gas samples collected in the ice cores from Antarctica.


Isotopes are actually different forms of an atom. Some of them are heavier than the other ones, and when you have an atom, you have always the same number of protons, but you can have different number of neutrons.

A mass spectrometer is an instrument which can distinguish between the different isotopes. In our case we try to distinguish between carbon 12 and carbon 13, and it’s doing that by magnetic field. So first of all it charges the particles and then there is a magnetic field, and because of the different charge of our isotopes they fly different ways and different distances in this instrument, and then you have a special detector sitting at the place where they should come out, and that is how you can then say, this is carbon 13, and this is carbon 12.

Phil Kendon