Mass Spectrometry

How is MS Done?

Basic MS Instrumentation

Magnetic Sector Mass Analyzers

Quadrupole Mass Analyzers

Reflector Time Of Flight

3D Quadrupole ion trap Linear Quadrupole ion trap

3D radio-frequency ion traps: ions are trapped in center point (single point)2D Linear trap: rf field is zero along the whole central line of the electrode configuration  

Quadrupolar ion traps (Paul trap)

3 sets of parallel plates in a uniform magnetic field

In a 7-Tesla magnetic field an ion with m/z =100 will spin 1,000,000 cycles (travel ~ 30 km) in a 1 sec. observation period

Fourier transform ion cyclotron resonance (FTICR) MS

Linear trapping quadrupole FTICR

Mass Analyzers

Instrument

Mass analyzer 2D trap QTOF FT-ICR/Orbitrap

Mass accuracy 500 ppm 10 ppm 1 ppm

Resolution 1,000 10,000 100,000

Sensitivity 0.1 fmol 1 fmol 0.1 fmol

Dynamic range 100 50 10,000

Price $250K $450K $600K

Electron Impact Vs Chemical Ionization

Electrospray Ionization

Electrospray Vs Electron Impact

Proteins/Preteomics

Matrix Assisted Laser Desorption Iionization (MALDI)

Resolution/Sensitivity/Mass Accuracy

MR =

ΔM

Mass

Mass Difference

5000 is typical

unit resolution up to mass 5000

Proteins: 100 AAM = 15,000R = 15,000 for unit resolution

Exact Mass/Mass Defect/Isotopic Abundance

C3H8O 60.05754C2H8N2 60.06884

C2H4O2 60.02112

CH4N2O 60.03242

R > 5300 required

base peak

molecular ion

Fragment

isotopepatterns

The Mass Spectrum

Isotope Patterns

CO 28 100 1.12 0.2N2 28 100 0.76 0.001C2H4 28 100 2.23

0.01

M+1 M+2M

Fragmentation

Alkanes

Cyclic Alkanes

Alkenes

Aromatics

Alcohols

Phenols

Aliphatic Ethers

Aromatic Ethers

Ketones

Aromatic Ketones

Aldehydes

Carboxylic Acids

Esters

Lactones

Thiols