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The Classic: Magnetic Sector Mass Analyzer

detector

Y+

heating coil

path of lighter ions

X+

vaporized sample

charged ion beam

Z+

path of heavier ions

electron source

magnetic field separates ions

accelerators

magnet

! Features

! Ion Trajectory

High resolution High sensitivity High dynamic range High-energy CID MS/MS spectra are very reproducible Not well-suited for pulsed ionization methods (e.g. MALDI) Usually larger and higher cost than other mass analyzers

Ions from the ion source are accelerated to high velocity though a magnetic sector, in which a magnetic field is applied perpendicular to the direction of ion motion.

Ion velocity then becomes constant but in a circular path at angles of180, 90, or 60°.

Ions are sorted mass to charge ratio by holding V and r constant while varying B

m z

=

B 2 r 2V 2 e

Time-of-Flight Mass Analyzer

! Features

Advantages: simplicity, ruggedness, ease of accessibilty to ion source, unlimited mass range and rapid data aquisition.

Disadvantages: Data aquisition must be fast, variations of in ion velocities can create peak broadening which can limit resolution

high voltage

sample

laser

detector

! m 3 3

! m 2 2

!1 m

1

source

drift region

! Ion Trajectory

m1

m2

m3

Ions are generated from electron, secondary ions, or laser generated photons

Ions are accelerated by an electronic field with equal E into a field-free drift tube ( L = 1m). Ions have different velocities due to differences in mass. Typical flight times are 1-30 µs.

!=

L t

m

2 2Vt

z

=

L2

t =L

m z2V

5

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