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An Introduction to Mass Spectrometry. e -. Carbon. 12 C = 12.000000. Hydrogen. 1 H = 1.007825. Nitrogen. 14 N = 14.003050. Oxygen. 16 O = 15.994914. Masses of Common Isotopes. CO. MW = 27.994914. N 2. MW = 28.006100. CH 2 =CH 2. MW = 28.031300. CO. N 2. CH 2 =CH 2. 27.994914.

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  1. An Introduction to Mass Spectrometry e-

  2. Carbon 12C = 12.000000 Hydrogen 1H = 1.007825 Nitrogen 14N = 14.003050 Oxygen 16O = 15.994914 Masses of Common Isotopes CO MW = 27.994914 N2 MW = 28.006100 CH2=CH2 MW = 28.031300

  3. CO N2 CH2=CH2 27.994914 28.006100 28.031300 28 28 1/100 28 28.0 28.0 1/1,000 28.0 1/10,000 27.99 28.01 28.03 Resolution of Masses Resolution

  4. Hydrogen 1H = 99.985% 2H =0.015% Carbon 12C = 98.90% 13C = 1.10% Nitrogen 14N = 99.63% 15N =0.37% Oxygen 16O = 99.762% 17O =0.038% 18O =0.200% Sulfur 32S = 95.02% 33S =0.75% 34S = 4.21% 36S =0.02% Chlorine 35Cl = 75.77% 37Cl = 24.23% Bromine 79Br = 50.69% 81Br = 49.31% Natural Abundance of Common Elements

  5. The Mass Spectrometer Focusing slits Accelerating voltage V Focused ion M+ Ion M+ Ionizing voltage Radius r Detector Sample inlet Low vacuum m/z = B2r2e/2V Where m = mass, e = electron charge, z = # of charges/ion r = radius of curvature Magnetic field B Increase B

  6. For carbon, One in ~90 atoms of carbon is C-13 For every 90 molecules of methane ...

  7. only one molecule contains C-13

  8. Where’s Waldo?

  9. … or for the C30 triterpene squalene

  10. one carbon in 3 molecules is C-13

  11. The Mass Spectrum of Methane M+ = 16 Molecular ion [C12H4]+. M+ = 15 C12H3+ [C12H2]+. C12H+ 16 M +1 = 17 [C13H4]+. [C12]+. 8 3 m/z 12 13 14 15 16 17 100 Base peak 86 1.11

  12. M = 43; M-43 base peak M = 57; M-29 n-hexane; MW 86 M = 29; M-57 molecular ion M+ 86 M = 71; M-15 M = 15; M-71 SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

  13. There are five constitutional isomers of C6H14 Which one of the remaining four has the following mass spectrum?

  14. M = 57; M-29 weak signal base peak M = 43; M-43 M = 29; M-57 weak signal M = 71; M-15 molecular ion M+ 86 M = 15; M-71 C6H14, MW 86 SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

  15. M = 57 M = 57 M = 57 M = 29 M = 29 M = 29 3-methylpentane 2-methylpentane M = 43 M = 71 M = 15 2,2-dimethylbutane 2,3-dimethylbutane The Four RemainingHexanes

  16. n -butyl radical (RH) BDE = 98 kcal/mol methyl radical (RH)  = +104 kcal/mol M = 87 M = 45 2-hexanol MW 102 SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

  17. Ethyl Bromide C2H5Br81 M = 29 C2H5+ C2H5Br79 SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

  18. Isopropyl Chloride i-PrCl37 i-PrCl35 M-15 M-15 SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/

  19. Back to squalene (C30H50) or (6E, 10E, 14E, 18E)- 2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene

  20. Pentenylpyrophosphate Farnesylpyrophosphate Squalene On the Mechanism of the Biosynthesis of Squalene 3 CH3CO2H

  21. CH3 CH3 Squalene C30 CH3 HO Cholesterol C27 On the Biochemical Conversion of Squalene to Cholesterol

  22. Farnesylpyrophosphate - d2 Squalene - d3 A Deuterium Labeling Experiment on the Biosynthesis of Squalene

  23. Oxidative Ozonolysis of Deuterium Labeled Squalene and succinic acid - d3 levulinic acid acetone

  24. -H2O -H2O Formation of Succinic Anhydride Succinic acid Succinic anhydride Succinic acid - d3 Succinic anhydride - d3

  25. Succinic Anhydride Succinic Anhydride-d3 M = 28 M = 56 M-31; C2D3H M = 59 M+ = 100 M - 44; CO2 M - 28; C2H4 M - 44; CO2 M+ = 103

  26. The End e-

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