2.5 Mass Spectrometry
39
2.5 Mass Spectrometry
39
2.5.10 Mass Correlation Table
Note: As long as it makes sense chemically, CH 2 , CH 4 , CH 3 O, and O 2 in the
formulae of the second column may be replaced by N, O, P, and S, respectively (M,
molar mass).
Mass Ion
Product ion
(and neutral
particle lost)
Substructure or compound type
1
[M+1] +
particularly in ESI spectra, in which
M±1 occurs even for moderately
basic and acidic compounds, but
intensive M +· without M±1 is unusual
7
Li +·
[M+7] +
in ESI spectra in the presence of Li +
(with isotope signal for 6 Li)
12
C +·
13
CH +
14
CH 2
+· , N + ,
N 2
++ , CO ++
15
CH 3
+
[M-15] +·
(CH 3 ) nonspecific; abundant: methyl,
N-ethylamines
16
O +· , NH 2
+ ,
O 2
++
[M-16] +·
(CH 4 )
(O)
methyl (rare)
nitro compounds, sulfones, epoxides,
N-oxides
(NH 2 ) primary amines
17
OH + ,
NH 3
+·
[M-17] +·
(OH) carboxylic acids (especially aromatic
ones), hydroxylamines, N-oxides,
nitro compounds, sulfoxides, tertiary
alcohols
(NH 3 ) primary amines
18
H 2 O +· ,
NH 4
+
[M-18] +·
(H 2 O) nonspecific; abundant: alcohols,
some acids, aldehydes, ketones, lactones, cyclic ethers
O indicator
19
H 3 O + , F +
[M-19] +
(F) fluoro compounds
F indicator
20
HF +· , Ar ++ ,
CH 2 CN ++
[M-20] +·
(HF) fluoro compounds
F indicator
21
C 2 H 2 O ++
22
CO 2
++