Midterm 2 Review

Question 1

What are ICP, ESI and MALDI used for?

Answer 1

Volatilization and ionization

Question 2

What are EI and CI used for?

Answer 2

Ionization

Question 3

What are quadrupole, TOF, fourier transform and ion traps used for?

Answer 3

Mass sorting

Question 4

What are electron multipliers used for?

Answer 4

Detection

Question 5

Isobaric Interference?

Answer 5

Results from equal mass isotopes of different elements present in sample solution

Question 6

How to correct isobaric interference?

Answer 6

Use relative gas that forms product with similar mass to that of the unwanted isotope

Question 7

Polyatomic Interference?

Answer 7

Combination of two or more isotopes from different elements in the same plasma

Question 8

How to correct polyatomic interference?

Answer 8

Use hexapole collision cell to remove unwanted molecules

Question 9

What are the 4 components of mass spec?

Answer 9

Sample inlet/volatilization
An ionization source
A mass analyzer
detector

Question 10

ICP Torch

Answer 10

very very hot and makes ions to use in MS. Analyte must be separated before entering ICP. Laser adsorption to produce ions. Plasma detected through cooling cone. Extraction lens attracts positive ions from plasma. Ions enter collision cell (with H2 or He). Ions guided to mass spec

Question 11

Interphase in MS?

Answer 11

Transport as many ions as possible to MS while excluding photons, neutrons and other unwanted particles that will produce unwanted signal.

Question 12

Quadrupole advantages and disadvantages

Answer 12

compact, tough, cheap, high scan rate, BEST sensitivity

WORST resolution, slow, maximum ratio

Question 13

Time of flight advantages and disadvantages

Answer 13

Simple, can combine with many ion sources, unlimited mass range, FAST

low sensitivity and resolution

Question 14

Double focusing advantages and disadvantages

Answer 14

BEST resolution, double focuses

Huge and expensive, requires extensive knowledge to operate

Question 15

3 main uses of MS

Answer 15

1. Analysis of pure compound (give molecular mass, dormula, isotopic ratio, fragmentation patterns
2. Mixture analysis (requires separation using GC-MS, LC-MS, CE-MS)
3. Quantification (requires internal standards and cal curve)

Question 16

Applications for molecular MS

Answer 16

pharmaceutical analysis, forensics, food safety

Question 17

Electron impact advantages and disadvantages

Answer 17

Cheap, touch, reproducible

rough on molecule, molecular ions do not survive, entire class of compounds does not work

Question 18

Exact Mass?

Answer 18

Calculated

Question 19

Accurate mass?

Answer 19

Actual measured m/z

Question 20

Chemical ionization?

Answer 20

a gaseous reagent is introduced into ionization region. Ionized carrier gas with EI and collides gas with analyte

Question 21

CI advantages and disadvantages

Answer 21

nice and gentle, molecular ion will survive, cheap

Molecule must be volatile, not reproducible, low polarity requires

Question 22

Electrospray Ionization (ESI)

Answer 22

used for large molecules where fragmentation is avoided.
Dispersal of fine spray charges droplets followed by solvent evaporation and ion ejection. Sample is injected into high voltage capillary and comes out as a highly charges mist. Solvent evaporated with N2. Molecular ions then repel each other and charged analyte is ejected into mass analyzer.

Question 23

Matrix Assisted Laser Desorption ionization (MALDI)

Answer 23

Analyte is mixed in matrix solvent and applied to metal plate. A laser light hits causing energy absorption. The analyte is ionized and ejected into gas phase and is then accelerated into chosen MS.

Very expensive but has HIGHEST m/z ratio

Question 24

Fourier transform ion-cyclotron MS (FTIC)

Answer 24

Used a magnetic field to trap ions into an orbit (centripetal force).

Question 25

Multiple reaction monitoring (MRM) vs Selected “” (SRM) vs product ion scan (PIS)

Answer 25

MRM/SRM monitors each precursor ion/product ion transition at a time.

SRM is monitoring only a single fixed mass window
MRM scans rapidly over multiple mass windows and thus acquires traces of multiple fragment ion masses

PIS used for qualitative applications to obtain structural information.
Q1 is set to allow only the transmission of one m/z. The parent ion collides with Argon gas in Q2 to create fragment or product ions. Product ions are scanned through Q3

All allow relative and absolute quantification of proteins, peptides and metabolites.