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33 Cards in this Set
- Front
- Back
charged molecules (molecular fragments) generated in high vacuum move across spectrometer based on m/z |
Mass Spectrometry |
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destroys sample into component functional groups |
Mass Spectrometry |
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very good sensitivity, LOD & LOQ (better than UV/Vis) |
Mass Spectrometry |
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Instrumentation of Mass Spec |
inlet -> ion source -> mass analysers -> detectors -> computer |
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sample introduction |
1. direct insertion probe 2. online with chromatography system |
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perpendicular movement of e- and sample collision knocks off sample e- leads to charge |
ionization |
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highly dependent on method of ionization |
appearance of mass spectra |
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ionization sources |
1. gas phase sources 2. desorption sources |
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sample is first vaporized then ionized |
gas phase sources |
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sample directly converted to gaseous ions |
desorption sources |
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ionizing agent for 1. electron impact 2. chemical ionization 3. field ionization |
1. energetic electrons 2. recent gaseous ions 3. high potential electrode |
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ionizing agent for 1. field desorption 2. electrospray ionization 3. matrix-assisted desorption ionization |
1. high potential electrode 2. high electrical field 3. laser beam |
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ionizing agent for 1. plasma desorption 2. fast atom bombardment 3. secondary ion mass spec 4. thermospray ionization |
1. fission fragments from 22Cf 2. energetic atomic beam 3. energetic beam of ions 4. high temperature |
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GPS vs DPS |
GPS: thermally stable compounds, small molecules DPS: nonvolatile & thermally unstable compounds, large moleculates |
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causes lot of fragmentation |
hard sources |
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impart sufficient energy on the analyte to leave the molecule in an excited state in w/c relaxation results in rupture of bonds |
hard sources |
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hard sources |
pyrrolidine derivative |
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causes little fragmentation w/ little peaks besides M peak |
soft sources |
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electron impact |
hard sources |
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chemical ionization |
partly hard sources |
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field ionization |
soft sources |
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bombardment w/ beam of energetic e- e- produced accelerate towards positive target (anode) |
electron impact |
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gaseous sample ionized by collision with ions produced by particle bombardment of an excess reagent gas |
chemical ionization |
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types of chemical ionization |
1. positive ion CI 2. negative ion CI |
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methane reacts with high energy e- |
PICI |
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reagent gas collides with e- to reduce energy, then captured by EN groups 10x more efficient than EI, 40x more sensitive |
NICI |
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heat first where sample is contained little fragmentation occurs ions formed under influence of large electric field |
field ionization |
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separate ions based on m/z |
mass analyzers |
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quadrupole mass analyzer |
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time-of-flight mass analyzer
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ion capture/trap mass analyzer |