1. Mass Spectrometry
CHEM HONORS

2. Mass Spectrometry
This is an analytical technique that helps identify how much of a given substance (chemical) is present in a sample by measuring the mass to charge ratio
A sample is bombarded by electrons, this causes the sample to fragment and form ions.
These ions are separated by their mass to charge ratio via an electric or magnetic field and are then detected.
Results are displayed in a spectrum containing the relative abundance of the detected ions.
The atoms or molecules can be determined by comparing them to known masses

3. Mass Spectrometry

4. What can you learn from Mass Spec?
Determine the elemental or isotopic signature of a sample
The masses of particles or molecules
Figure out the chemical structure of molecules

5. Mass Spectrum of Boron

6. Mass Spectrum of Boron 10B – 23 (relative abundance)
1.) Add the two relative abundances to get a total abundance [ = 123]
2.) Divide the relative abundance by the total abundance and then multiply the value by 100%
3.) Multiply the both masses by their respective percent abundance
4.) Add the two values together to determine the relative atomic mass

7. Mass Spectrum of Zirconium

8. Determining Atomic Mass
If there is…..
90Zr % abundance
91Zr %
92Zr %
94Zr %
96Zr %
What is the atomic mass of Zr?

9. Mass Spectrum of Cl2
Sometimes the diatomic molecule, Cl2, does not fragment all the way
Chlorine has two isotopes, 35Cl and 37Cl, and will also have three different diatomic molecules:
35Cl – 35Cl
35Cl – 37Cl
37Cl – 37Cl

10. Mass Spectrum of Cl2