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The flashcards below were created by user
bkkrafft
on FreezingBlue Flashcards.
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Name some of the forensic applications of mass spectroscopy.
- Drug Analysis (cocaine, hash, LSD)
- Toxicology (poisons, alcohol, mace)
- Arson (petroleum, alcohol based ignitable liquids)
- Explosives (nitro-substituted benzenes, TATP)
- Trace Analysis (polymers, adhesives, general unknowns)
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What is a mass spectrometer?
An analytical instrument which creates charged particles from molecules, separate ions, and detect ions.
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A mass spectrometer separates ions according to which ratio?
mass to charge (m/z)
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What are the 2 gas-phase methods of ionization?
- Electron Impact
- Chemical Ionization
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What are the 2 spray methods of ionization?
- Electrospray
- Atmospheric Pressure Chemical Ionization
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What are the 2 desorption methods of ionization?
- Fast Atom Bombardment
- Matrix-Assisted Laser Desorption Ionization
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How is the molecular ion formed in electron-impact?
it is the result of a high energy electron colliding with a molecule forcing the loss of an electron from the molecule
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T/F: Molecular ions may degrade further to smaller fragment ions as a result of residual energy from the electron impact process.
True!
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______ of the filament in the source causes the emission f electrons which are accelerated towards the anode in the ______ ______ ionization technique.
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Name some of the advantages of electron impact.
- Well-established
- Fragmentation libraries exist
- Interface to GC
- Non-Polar Samples
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Name some of the disadvantages of Electron Impact.
- Parent Identification
- Need volatile sample
- Need thermal sample
- Low mass compounds (<1000 amu)
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Define radicals
an atom or group of atoms that has at least one unpaired electron and is therefore unstable and highly reactive
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Define neutrals
a particle that has neither positive nor negative electric charge; a net electric charge of zero
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Define cations
an ion or group of ions having a positive charge and characteristically moving toward the negative electrode in electrolysis; even electron species
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Define radical ion
a charged compound that has an unpaired electron; it may be either a radical cation or radical anion; odd electron species
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What is the most common and simplest fragmentation?
bond cleavage resulting in neutral radicals and a cation
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What is the less common fragmentation type?
An even-electron neutral is lost and results in odd-electron radical cation fragment ion
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What is heteroatom participation?
the presence of a functional group containing a heteroatom (N, S, O, X) can alter the fragmentation pattern
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Between what 2 things do the ion molecule reactions occur in chemical ionization?
- ionized reagent gas molecules
- volatile analyte neutral molecules
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In positive ion mode of chemical ionization, is a proton added or subtracted?
Added
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What are the advantages of the chemical ionization technique?
- parent ion presence
- interface to GC
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What are the disadvantages of the chemical ionization technique?
- no fragment library
- need volatile sample
- need thermal stability
- low mass compounds (<1000 amu)
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What is the nitrogen rule?
Ions without N atoms or those with an even number of N atoms have an even numbered mass, and the majority of the fragment ions have odd masses.
Ions with an odd number of N atoms have an odd numbered mass and the majority of the fragment ions have even masses.
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T/F: The presence of bromine or chlorine in a molecule or ion are not easily detected by the intensity ratios of ions differing by 2 amu.
False! They can be easily detected by the intensity ratios differing by 2 amu.
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What 2 ions are included in the 50:50 mixture of bromine?
79Br and 81Br
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What 2 ions are included in the 75:25 mixture of chlorine?
35Cl and 37Cl
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