Mass Spectrometry

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Slide 1

Mass Spectrometry

Slide 2

Purpose of Mass Spectrometry

Produces spectra of masses from the molecules in a sample of material, and fragments of the molecules.

Used to determine

the elemental composition of a sample

the masses of particles and of molecules

potential chemical structures of molecules by analyzing the fragments

the identity of unknown compounds by determining mass and matching to known spectra

the isotopic composition of elements in a molecule

Slide 3

Stages

The ionizer converts some of the sample into ions.

Mass analyzers separate the ions according to their mass-to-charge ratio.

The detector records either the charge induced or the current produced when an ion passes by or hits a surface

Slide 4

Mass Spectrometry Methods

http://www.chem.arizona.edu/massspec/intro_html/intro.html

Slide 5

Mass Spectrum of CO2

Molecular ion peak

[CO2]+ = 44

[CO]+ = 28

[O]+ = 16

[C]+ = 12

Fragment Peaks

Slide 6

Mass Spectrum of Bromine, Br2

Bromine has two isotopes: 50.69% 79Br and 49.31% 81Br

79Br+

81Br+

[79Br81Br]+

[79Br79Br]+

[81Br81Br]+

Molecular Ion Peaks

Fragments

Slide 7

Practice: Methyl Bromide, CH3Br

Slide 8

Answers: Methyl Bromide, CH3Br

[CH381Br]+

[CH281Br]+

[C81Br]+ and [CH279Br]+

[CH81Br]+ and [CH379Br]+

[CH79Br]+

[CH3]+

[C79Br]+

[81Br]+

[79Br]+

Slide 9

Practice: Methylene Chloride (CH2Cl2)

Chlorine is 75.77% 35Cl and 24.23% 37Cl

Slide 10

Practice: Vinyl Chloride (CH2CHCl)

Chlorine is 75.77% 35Cl and 24.23% 37Cl

Slide 11

Spectra of Larger Molecules

Spectra of large molecules have many fragments, and the interpretation of their spectra is beyond the scope of this course.

Codeine, C18H21NO3

Slide 12

Toluene ( C7H8) Fragmentation