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IA CH 20 Mass Spectrometry
Terms, Def and Theory
29
Chemistry
Undergraduate 4
12/18/2013

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Term
Define Hard Ionization
Definition
Sources that imparts enough energy to an analyte molecule to leave them in a highly exited energy state. Relaxation involves rupture of bonds producing fragment
Term
Define soft ionization
Definition
source imparts lesser extent of energy resulting fewer fragments
Term
Define molecular ion peak
Definition
tells molecular weight
Term
Define base peak
Definition
represent most stable ion, fix to 100%
Term
Define fragment peaks
Definition
how the molecule breaks up
Term
Draw the mass spec system
Definition
do on separate sheet of paper
Term
Define Inlet
Definition
How the sample is introduced
Term
What are the two types of inlets for a mass spec?
Definition

1) Direct probe

2) connection to separation system

Term
Define Direct probe
Definition
introduction of sample manually
Term
Scenarios for direct probe use
Definition
-want sample directly in ms
-starting with pure sample
-have minimal sample
Term
Define connection to a separation system
Definition
up front separation using
GC- organics
ICP- inorganics
HPLC- anything molecular
Term
What are the two types of ion sources?
Definition
1) gas phase source
2) desorption source
Term
What are the two gas phase sources in MS
Definition

1) Electron impact

2) Chemical ionization

Term
Describe electron impact
Definition
-bombard molecule with ton of electrons
-hi detection limit, only 1 per million ionzied
-destructive
Term
Draw the Electron impact system and the chemical reaction involve
Definition
Separate sheet of paper
Term
Describe chemical ionization
Definition
Gaseous atoms of the sample are ionized by collision w/ ions produced by electron bombardment of excess reagent gas
Term
Write out the chemical ionzization reactions(general, proton transfer and hydride transfer).
Definition
Refer to book and notes
Term
Describe desorption source
Definition
-used for non volatile and thermo stable molecules
-used for high molecular weight samples
Term
Describe how MALDI works
Definition
1)Evaporate sample on MALDI matrix
2)Place sample matrix in vacuum
3)Hit matrix with laser, matrix absobs photon and transfers energy to sample
4) Ion plume goes to mass azalyzer
Term
What are the three types of mass analyzers
Definition
1) quadrapole
2) Time of flight
3) ion trap
Term
Draw a quadrapole
Definition
Refer to book and notes
Term
Explain a quadrapole
Definition
Altering the RF to DC ratio in the four parallel electrode you can alter the oscillation patterns of the ions and select for a narrow range of m/z
Term
What are the advantages and disadvantages of the quadrapole
Definition
advantage: fast scan rate, low detection limit
disadvantage m/z limit of 3000-4000
Term
Explain Time of flight
Definition
A spatially tight bunched group of ions produced by MALDI is accelerated in a drift tube where separation occurs based on velocity. (.5mv^2=KE)
Term
What are disadvantages of Time of flight
Definition
-Molecules are constantly stream towards detector
-low sensitivity
-requires good electronics
Term
Draw Ion Trap
Definition
Refer to book and notes
Term
Explain how ion trap works
Definition
Ions with specific m/z are stabilized between two ring electrodes before the RF is change to kick out ions
Term
Define mass selective ejection
Definition
sequentially ejects ions in order of increasing mass by increasing RF-voltage to ring electrode
Term
List the 11 applications for mass spec:
Definition
1)Elucidation of the structure of organic and biomolecules
2)determination of the mw of biomolecules
3)ID of components in TLC
4)Determination of aa squence in polypeptide
5)Detection and ID of species separated by chromatography
6)ID of drugs and metabolites in blood urine and saliva
7)Monitoring gases in surgery patients
8)dating archaeological specimens
9)analysis of aerosols
10)determination of pesticide residues in food
11)monitoring volatile organics in water supplies
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