Ch_322a_9.016

Ch_322a_9.016 - Mass Spectroscopy Mass spectroscopy is a...

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Mass Spectroscopy Mass spectroscopy is a very powerful analytical tool, especially when coupled with gas chromatography. The components of a mixture are separated by GC and then fed into a mass spectrometer where valuable composition and structural information is obtained on each of the components. The Fundamentals of MS Bombardment of a neutral molecule, M , with a beam of low energy electrons causes ionization to a radical cation : M + e - M + . radical cation + 2 e - 10-70 eV in energy 1 eV = 23 kcal/mol Note: M is energized by the interaction with e - and an electron is lost from the neutral molecule producing a radical cation.
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Fragmentations The initially formed radical cations are called "parent" ions . They essentially have the mass of M . A-B + e - A-B + . (-2e - ) parent A + + B . cation radical A + B + . cation radical The parent ions may fragment to smaller subunits of the original structure sometimes called "daughter ions." Only charged species are observed in the mass spectrum. In the above example, the parent A-B + . , and the two daughter ions A + and B + would be observed.
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Components of a Mass Spectrometer The components are in a high vacuum. A beam of molecules is introduced from a heated inlet into the ionization region
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This note was uploaded on 07/22/2009 for the course CHEM 322AL taught by Professor Jung during the Summer '07 term at USC.

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Ch_322a_9.016 - Mass Spectroscopy Mass spectroscopy is a...

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