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Mass Spectrometry 12-1 to 12-4

Mass Spectrometry 12-1 to 12-4. 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. Advantages.

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Mass Spectrometry 12-1 to 12-4

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  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 verysmallsamplesize + 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

  5. http://www.epa.gov/ada/about/pics/gc_lc_ms.jpg

  6. Take that, you foul machine! http://www.underthepier.com/images/16_smashing-fruits.jpg

  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 http://www.asms.org/whatisms/p1.html

  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

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

  10. Detailed Fragmentation of Methane

  11. Billiards Analogy? http://www.albany.edu/news/photo_archive/albums/reslife/images/billiards.jpg

  12. Piniata? http://www.roystory.com/images/Jimmy%5F5/pages/piniata_jimmy2.html

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

  14. High Resolution MS can determine molecular formula M.W. = 44 C3H8 3(12) + 8(1.007825) = 44.0626 C2H4O  2(12) + 4(1.007825) + 15.994914 = 44.026214 N2O  2(14.003050) + 15.994914 = 44.001014 CO2 12 + 2(15.994914) = 43.989828

  15. Some atoms reveal their presence by isotope patterns

  16. Fragmentation of Alkanes http://www.lobos.nih.gov/cbs/img/alkane.jpg

  17. MS fragmentation of pentane

  18. MS fragmentation of pentane

  19. Dimethylpentane

  20. hexane

  21. Fragmentation of molecules with oxygen and/or nitrogen http://www.chemistry.unimelb.edu.au/staff/chutton/research/Image15.gif

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

  23. However, Fragment abundance is difficult to predict

  24. Gas ChromatographyMass Spectrometry GC GC MS

  25. MS  Molecular Structure

  26. MS fragmentation of 2-pentanone

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

  28. MS fragmentation of 2-pentanone

  29. Time-of-Flight Instruments http://www.uibk.ac.at/ionen-angewandte-physik/umwelt/research/pics/animation.gif

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