Mass Spectrometry Introduction
Mass
Analyzer
Detector
Intensity
Ion
Source
Ion Abundance
Components of a Mass Spectrometer
500
400
300
200
100
0
600
800
1000
1200
1400
m/z
m/z
1
Periodic Table Masses vs. Isotope Masses
Element
Mass on Periodic Table
Mass of most abundant isotope
C
12.011
12.0000 (12C)
H
1.0079
1.0078 (1H)
N
14.0067
14.0031 (14N)
O
15.9994
15.9949 (16O)
S
32.06
31.9721 (32S)
P
30.9738
30.9738 (31P)
Cl
35.453
34.9689 (35Cl)
Mass Defect (x 10‐3 u)
Mass Defect across periodic table
Element
2
Isotopes of Dextromethorphan (M+H)+
Mass Spectrum of Dextromethorphan (M+H)+
Relative Ion Abundance
(12C181H2616O14N)+
(12C17 13C 1H26 16O 14N)+
(12C18 1H25 2H 16O 14N)+
(12C18 1H26 16O 15N)+ 12 13 1 16 14 +
( C16 C2 H26 O N)
(12C17 13C1 1H26 16O 15N)+
…
m/z
3
Ion Abundance
Mass Spectrum of Dextromethorphan (M+H)+
(higher resolution)
m/z
Natural Isotope Abundances
Element
Isotope
% Relative Abundance
C
12C
98.93
1.07
99.9885
0.115
99.757
0.038
0.205
99.632
0.368
94.93
0.76
4.29
0.02
75.78
24.22
13C
H
1H
2H
O
16O
17O
18O
N
14N
15N
S
32S
33S
34S
36S
Cl
35Cl
37Cl
4
Why Isotope Patterns Matter
(C18H26NO)+
(C17H19NCl)+
(C10H14N3O6)+
Isotope Patterns of Large Molecules
Renin substrate peptide
C85H124N21O20
(M+H)+
Relative Ion Abundance
monoisotopic
monoisotopic mass = 1758.92
average mass = 1760.04
most abundant peak = 1759.92
m/z
5
Isotope Patterns of Large Molecules
Relative Ion Abundance
Glucagon
C153H224N42O50S
(M+H)+
monoisotopic mass = 3482.60
average mass = 3483.49
most abundant peak = 3484.60
monoisotopic
m/z
Isotope Patterns of Large Molecules
Relative Ion Abundance
Apomyoglobin
C769H1212N210O218S2
(M+H)+
monoisotopic mass = 16941.97
average mass = 16952.50
most abundant peak = 16952.00
monoisotopic
m/z
6