How is your fingernail sample prepared and analyzed?

1. About 1 milligram of your fingernail clippings will be put into a tiny tin foil capule, which will then be crushed closed.
2. The tin capsules are loaded into an automated sampler which will drop the samples, one by one, in to a furnace heated to 1100º C where the sample is instantly combusted to CO₂, N₂, H₂O, and other gases.
3. A flow of helium then carries the gases through scrubbers that remove unwanted gases, and a gas chromatograph column that separates the remaining CO₂ and N₂ gases so that they can be separately analyzed (Figure 2).
4. The gases then flow into the mass spectrometer where the isotope ratios of CO₂ (¹³C/¹²C) and N₂ (¹⁵N/¹⁴N) are measured.
5. A computer controls the mass spectrometer, collects the data, and calculates the isotope ratios from the small voltages measured.