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Transpector MPS Operating Manual
Some elements have many intense isotopes (e.g., xenon is 0.096% mass 124,
0.090% mass 126, 1.92% mass 128, 26.44% mass 129, 4.08% mass 130, 21.18%
mass 131, 26.89% mass 132, 10.44% mass 134, and 8.87% mass 136).
Isotope ratios, like fragmentation patterns, are a very useful aid in recognizing
specific materials. Under normal ionization conditions, the peak height ratios for the
various isotopes of an element will be the same as the ratios of their natural
abundances. That is, the probability of ionizing, for example, the mass 35 isotope
of chlorine (
35
Cl) is the same as the probability of ionizing the mass 37 isotope
(
37
Cl). Thus, the peak height ratio of mass 35 to 37 from HCl will be 3.07 to 1
(75.4% / 24.6%).
For a listing of the isotopic ratios for the lighter elements, see
. For a
complete listing of the natural abundances for the isotopes of all the elements, see
the
Handbook of Chemistry and Physics
from CRC Press.
Table 4-2 Isotope ratios
Isotope Ratios
Element
Mass No.
Relative
Abundance
H
1
99.985
2
0.015
He
3
0.00013
4
~100.0
B
10
19.78
11
80.22
C
12
98.892
13
1.108
N
14
99.63
15
0.37
O
16
99.759
17
0.0374
18
0.2039
F
19
100.0
Ne
20
90.92
21
0.257
22
8.82
Na
23
100.0
Al
27
100.0
Si
28
92.27
29
4.68
30
3.05
P
31
100.0
S
32
95.06
33
0.74
