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Flashcards in Mass Spectrometry Deck (47)
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1

What steps may be required to prepare samples for MS?

Sample prep:
homogenization, dry/weigh, extraction (LLE, LPME, SPE...), purification/clean up, preconcentration, chem. modification (if needed)

separation:
LC, GC, IC, CE, FFF...


*or can be direct analysis

2

How is exact atomic mass different from the molecular mass?

molecular mass is AVERAGE from relative abundance of various natural isotopes

each natural isotope for a element will have a different exact mass

3

What are the most abundant forms of H, C, N, O, and S?

1H, 12C, 14N, 16O, 32S

4

What is the y and x axis in a mass spectrum?

y axis: relative intensity
x axis: m/z

5

What is m/z?

mass to charge ratio
(divide mass number of ion by charge number)

6

What environment is necessary for mass spectrometry?

vacuum (10-5 to 10-8 torr)

7

What are the general parts of a mass spectrometer? (6)

inlet system (connect to GC, LC....)
vacuum system
ion source (produce gas-phase ions)
mass analyzer (ions separated according to m/z)
detector (collect/convert specific ions into electric signal w/ ion transducer)
computer/signal processor (control + collect/analyze data)

8

The MS is connected to the LC or GC or CE by the ___ ____

inlet system

9

Where are the ions separated in the MS?

Mass analyzer (separate according to m/z)

10

The detector will _____ ions with a certain ____, and convert into an electric signal using a ___ _____

collect
m/z
ion transducer

11

What are common ion sources for mass spectrometry? (5)

gas phase:
- electron impact (EI)
- Chemical ionization (CI)

Desorption:
- Fast atom bombardment (FAB)
- matrix assisted laser desorption/ionization (MALDI)
- Electrospray ionization (ESI)

12

What is the method of ionization for EI? what type of spectra does it produce?

energetic electrons

fragmentation patterns

13

What is the method of ionization for CI? what type of spectra does it produce?

reagent gaseous ions

proton adducts, few fragments

14

What is the method of ionization for FAB? what type of spectra does it produce?

energetic atom beam

molecular ions and fragments

15

What ionization type produces proton adducts?

chemical ionization

16

What method of ionization uses high energy photons?

MALDI

17

what type of spectra does MALDI produce?

molecular ions, multiply charged ions

18

What ionization methods can produce multiply charged ions?

MALDI
ESI

19

What is the method of ionization for ESI? what type of spectra does it produce?

electric field produces charged spray, which desolvates

multiply charged molecular ions

20

ESI can be in ___ or ___ mode

positive
negative

21

describe the process of EI ionization:

hit molecular ion with electron (M + e-)
produces molecular ion
M+ + 2e-

*relaxation of M+ will result in some fragmentation

22

What is EI ionization usually paired with? (separation technique)

GC

23

What ions can ESI (positive mode) produce? (6)

M+ (if it exists);
[M+H]+
[M+2H]2+
[M+3H]3+
[M+NH4]+
[M+Na]+

24

What ions can ESI (neg mode) produce?

deprotonation [M-H]-

25

ESI is usually paired with ____ separation

LC

26

What are common mass analyzers for MS? (6)

Magnetic sector
double focusing
quadrupole
ion trap
ion cyclotron resonance
time-of-flight

27

What are 'mass filters?'

another name for mass analyzers

28

What is the principle of magnetic sector mass filters?

deflect ions in magnetic field (trajectory depends on m/z value)

29

What is double focusing?

1. electrostatic focusing
2. magnetic field deflection

30

What is the principle of quadrupole mass filters?

ion motion in dc and radiofrequency fields - only certain m/z ions pass through