1. Mass Spectrometry 12-1 to 12-4

2. What does MS do? Analysis technique that reveals:
Molecular Weight of a pure compound
Molecular Formula (High Resolution MS)
Some structural information
“Chemical Fingerprint” that can be matched to a known compound.

3. Advantages + Very very small sample size
+ Can be coupled with Gas Chromatography
+ Complementary to UV/vis, IR, NMR
+ Versatile: many techniques have been
developed, from small organics to proteins and DNA.
+ Data base friendly

4. Disadvantages - Destructive to sample - Limited structural information
- Too sensitive – background noise a problem
- Expensive & Sophisticated instrument

6. Take that, you foul machine!

7. Applications Detect and identify the use of steroids in athletes
Monitor the breath of patients by anesthesiologists during surgery
Determine the composition of molecular species found in space
Determine whether honey is adulterated with corn syrup
Locate oil deposits by measuring petroleum precursors in rock
Monitor fermentation processes for the biotechnology industry
Detect dioxins in contaminated fish
Determine gene damage from environmental causes
Establish the elemental composition of semiconductor materials

8. How does MS work?
Electron Impact Ionization if most popular fragmentation technique
A stream of high energy electrons are directed towards organic molecules
The electrons fragment the molecules in rational and repeatable ways
Positive ions that are produced are separated by their mass to charge ratio

11. Gas Chromatography and
Mass Spectrometry (GC-MS):
A match made in analytical chemistry heaven

12. Detailed Fragmentation of Methane

13. Billiards Analogy?

14. Piniata?

15. Spectra and Data Table for the Electron Ionization of Methane

16. High Resolution MS can determine molecular formula
M.W. = 44
C3H8  3(12) + 8( ) =
C2H4O  2(12) + 4( ) =
N2O  2( ) =
CO2  ( ) =

17. Some atoms reveal their presence by isotope patterns

19. Fragmentation of Alkanes

20. MS fragmentation of pentane

22. MS fragmentation of pentane

23. Dimethylpentane

24. hexane

26. Fragmentation of molecules with oxygen and/or nitrogen

27. Unshared Electrons on “O” and “N”
usually get knocked off first
Fragmentation occurs in a chemically rational and predictable way

29. However, Fragment abundance is difficult to predict

31. Gas Chromatography Mass SpectrometryGC GC MS

32. MS  Molecular Structure

33. MS fragmentation of 2-pentanone

34. m/z = 43
m/z = 87
m/z = 71
m/z = 58

35. MS fragmentation of 2-pentanone

36. Time-of-Flight Instruments