MASS SPECTROMETRY - A DETAILED PPT

K. Srinivasan

The Five Mass Spectrometry Nobel Prize Winners

Mass Spectrometer

Main Components of the Mass Spectrometer

IONIZATION

SOURCE

MASS

ANALYZERMASS

DETECTOR

Ionization Source

FRAGMENTATION PATTERNTHE FINGERPRINT OF CHEMICAL COMPOUNDS

Mass Analyzer

DC

DC

m1m3m4 m2

m3

m1

m4

m2

The cations that are formed are separated by magnetic deflection.

Only cations are detected

The amount of deflection observed depends on the mass to charge ratio

(m/z)

Separation is based on the difference

in mass-to-charge ratio (m/z)

Mass Analyzer

Mass Detector

X axis

Y axis

Mass Spectrum

CH3COCH3

Sample

Inlet

CH3+COCH3

Ionization

& Adsorption

of Excess Energy

Mass Analysis

CH3C+OCH3

+COCH3

+CH3

+COH

Fragmentation

(Dissociation)

Detection

The mass spectrum is a graph of the mass of each cation

vs. its relative abundance.

• mixture of ions of different mass gives separate peak for each m/z

• intensity of peak proportional to percentage of each atom of

different mass in mixture

• separation of peaks depends on relative mass

Mass Spectrum

20 40 60 80 100 120m/z

m/z = 78

100

80

60

40

20

0

Relative intensity

Some molecules undergo very little fragmentation

Benzene is an example. The major peak corresponds to the molecular ion.

Alkanes undergo extensive fragmentation

m/z

Decane

142

43

57

71

85

99

CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH3

Relative intensity

100

80

60

40

20

0

20 40 60 80 100 120

NIST LIBRARY

A MASS SPECTRUM DATABASE

GC - MS

LC - MS

sample cone

skimmer cone

instrument housing

mass/charge

discriminator

detector

atmospheric

pressure

“fore” vacuum

10-4 bar

high vacuum

10-7 bar

Shared components

of all ICPMS machines

ICP - MS

MS/MS means using two mass analyzers (combined

in one instrument) to select an analyte (ion) from a

mixture, then generate fragments from it to give

structural information.

Ion

sourceMS-2MS-1

Mixture of

ions

Single

ion

Fragments

GC – MS/ MS

APPLICATIONS

Fatty Acids Present in Snack Foods

Drug Abuse

Nutraceuticals/ Functional Foods

Mass Spectrometry, O. David Sparkman, Global

View Publishing (2012)

LC/MS: A Practical User's Guide, Marvin C

McMaster, Wiley(2011)

Liquid Chromatography – Mass Spectrometry:

An Introduction, Robert E. Ardrey, Wiley (2009)

Mass Spectrometry: A Foundation Course, K.

Downard, RSC (2004) (ISBN 0854046097) Mass

Spectrometry: Principles and Applications,

Edmond de Hoffmann & Vincent Stroobant, 2

nd Ed., Wiley (2001)

REFERENCE

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