Mass spectrometer

What does a mass spectrometer do?

1. Measures masses of atoms and molecules

2. Produces positive ions that are deflected in magnetic field according to mass to charge ratio

3. Calculates relative abundances of each positive ions

Step 1 in mass spectrometer

Heater vaporizes the sample so that particles can move through the machine

Step 2 in mass spectrometer

Vapor is bombarded with high energy electrons, resulting in one or more electrons being removed from the atoms, to form positive ions.

Step 3 in mass spectrometer

Electric field causes positive ions to accelerate

Step 5 in mass spectrometer

Positive ions deflect in the uniform magnetic field. The amount of deflection depends on the mass to charge ratio

Diatomic molecules and mass spectrometer

Diatomic molecules can be broken down into single atoms which are detected.

Diatomic molecules’ abundances are based on the abundances of combination of single atoms

Polyatomic molecule and molecular ion peak

There is a small number of C-13 isotopes which can lead to M+1 peak (only in very large molecules)

Why is mass spectrometer operated under a vacuum

So the only particles being detected are those in the sample, none from air.

How does a mass spectrometer help differentiate between isotopes?

By deflecting positive ions and separating them due to their mass to charge ratio.

Mass spectrometer labeled