Question

You have been asked to determine the composition of gases generated from an anaerobic digester which is thought to contain primarily, CO, methane, H2, and H2S.  Which GC detector would you use and why?

Answer 1

Methane can be detected by the use of flame ionization detector (FID).

Explanation:

Flame ionization detectors response depends on conducting power of ions or electrons produced on burning of organic compounds vor hydrocarbons in the flame.

For this, the sample must be combustible.

Methane is combustible and hence it can be detected by FID in the mixture of gases.

FID detector gives no response to inorganic and permanent gases such as CO, N2, etc.

CO, H2 and H2S can be detected by thermal conductivity detector (TCD).

Explanation:

The response of TCD detector depends on the thermal conductivity difference between the carrier gas and eluted samples.

This detector is widely used to detect inorganic gases such as CO, H2, and H2S.