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6.6. MASS SPECTROMETRY
(MS)
Mass spectrometry methods are extremely powerful and much used in
biochemistry to determine accurate masses, from which chemical information
often can be obtained. This also applies for oligomers (peptides,
oligosaccharides..), whereas it is still a challenge to accurately separate and
quantify large polymers, especially polydisperse systems.
Below are just given a few keywords to provide a general background:
'Time-of-flight' (TOF) instrument:
Source region: Analyte becomes ionized (positively charged)
Electric field (E) => acceleration => kinetic energy:
K = ZeEs
Ze = charge (after ionization), s = distance (source)
Ionized molecules enter the drift region:
K = (1/2)mv
2
= ZeEs =>
v
=
2
ZeEs
m
⎛
⎝⎜
⎞
⎠⎟
1/2
Migration time t:
⊕
⊕
⊕
Source
region
Drift region
Detecto
r
+
E