as illustrated in Fig. 4.29) or to use the exact composition for very sensitive
detection. However, most measurements in Organic Geochemistry are performed
as low-resolution mass spectrometry.
Finally, one modern development in mass spectrometry needs to be addressed,
the linkage of several mass spectrometer units in one device also known as
multidimensional mass spectrometry. Most common is the MSxMS technique
(also called tandem MS) linking two mass spectrometric units or mass analyzer,
e.g. two quadrupol analyzer or a quadrupol-ToF combination (see Fig. 4.30). The
clue is related to the ionization methods. Normally a first analyzer uses soft
2. mass peak
Δm
resolut ion
R = m / Δm
1. mass peak
peak width
Fig. 4.28 Illustration of
mass resolution
Table 4.4 Exact masses of
elements highly relevant in
organic chemistry
Element
Isotope
Dalton (Da)
Hydrogen
1
H
1.0078250
Carbon
12
C
12.000000
Nitrogen
15N
14.003074
Oxygen
16
O
15.994914
Chlorine
35
Cl
34.968854
Table 4.5 Nominal and exact masses of selected organic pollutants
Compound
Exact mass
Nominal mass
Hexachlorbenzol (
12
C 6
35
Cl 6 )
281.81312
282
Carbamazepin (
12
C 15
1
H 12
14
N 2
16
O)
236.09496
236
2,3,7,8-Tetrachlordibenzo-p-dioxin (
12
C 12
1
H 4
35
Cl 4
16
O 2 )
319.89655
320
4.2 Mass Spectrometry MS
69