Question

Often times you will want to anaylze a solid compound using IR. You may dissolve a sample in a suitable organic solvent and then pipet a small amount out and let the solvent dry before acquiring data. When doing this, why is is important to not hurry the eveporation process by blowing on the sample?

Answer 1

Infrared (IR) spectroscopy is used to identify the functional groups present in the unknown sample. For a molecule to be IR active it should have a dipole moment. While recording liquid samples IR spectroscopy, one should not hurry to evaporate the solvent by blowing, this is because by blowing the sample under observation may contaminate with carbon dioxide (CO₂). Carbon dioxide is IR active and hence the IR spectrum of the compound will have CO₂ peaks also.