Advanced Analytical Chemistry

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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy

• Chapter 8 Tandem Mass Spectroscopy
• References
• K.L. Busch et al., Mass Spectrometry/Mass
  Spectrometry Techniques and Application of
  Tandem Mass Spectrometry, 1988, VCH Publishers,
  Inc.

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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
M1x, M1y,.
MS
M1x, M1y,.
M1, M2,.
GC-MS
MS-MS
M1, M2
M1x, M1y,.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
GC-MS/MS
M1a, M1b..
M1, M2,.
M1ax, M1ay,.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
1. Theory 1.1 Formation of daughter ions The
general equation mp ? md mn 1 mp is
referred to as the parent ion. Molecular ion is
the ion, which has the mass equivalent to the
molecular weight of the compound, introduced into
the ion source. Parent ion need not to be
molecular ions. Both molecular ions and fragment
ions can be selected as parent ions in MS/MS.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy

• MS/MS experiment can be described as
• Mass selection of a parent ion in the first stage
  of analysis within the instrument, and then
• Analysis of the daughter ions often formed in a
  collision - induced dissociation (CID) process,
  in the second stage of analysis.

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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
Two processes used to provide the energy for
reaction 1. (1) Metastable ions Excess energy
deposited in the parent ion during the ionization
process. Metastable ions An ion with the
appropriate dissociation rate versus internal
energy content may survive long enough to be
extracted from the ion source before it
fragments, but may then fragment prior to
detection. Such ions are called metastable ions.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy

• Limitation of using metastable ions
• the percentage of metastable ions relative to all
  ions leaving the ion source is generally very
  small, and the time the ion spend in the reaction
  regions is generally only a small percentage of
  the total transit time through the MS.
• The metastable ions are characterized by a
  relatively narrow range of internal energies,
  therefore there are few fragmentation routes that
  are available for their decomposition.

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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
(2) Collision-induced dissociation (CID)
Admit a collision gas to a reaction region to
induce dissociations by collision of the parent
ion with the neutral target gas. This process is
called Collision-induced dissociation (CID).
N mp md mn 2 here the
only difference from 1 is the extra energy
imparted to mp , in this case by collision with
neutral target gas N.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
1.2. Types of dissociation reactions (1)
N mp ? md mn 3 (2)
Charge striping N mp ? mp2
e- 4 The process involves the loss of an
electron from the parent ion rather than the loss
of neutral fragment. The loss of an electron from
a positive ion usually requires substantially
more energy than does a dissociation process.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
(3) Neutralization-reionization Nx
Ny mp ? mp ? md
mn 5 The parent ion is first neutralized and
subsequently reionized in a collision. Useful
process in detailed ion structural studies. (4)
Charge inversion N mp- ? md
mn 2e- 6
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
1.3 Instrument design 1.3.1 Daughter ion
scan The parent ion mass is fixed and the masses
of all daughter ion formed from the parent ion
are measured. The first stage of analysis
selects ions of particular m/z. This parent ion
is passed onto the reaction region. The daughter
ions formed in the reaction region are then
analyzed by mass. These daughter ions are
generally characteristic of the structure of the
parent ions and thus provide a means of
determining that structure.
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
1.3.2 Parent ion Scan The first spectrometer is
scanned, while the second one is set to the mass
of one of the daughters. Closely related
compounds usually give several of the same
daughters, so that this method of operation
provides a measure of identity and concentration
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy

• MS/MS Instrumentation
• MS/MS spectrometers are made up of various
  combinations of magnetic sectors, quadrupole
  separators. These are low resolution separators.
  High resolution, such double-focusing instruments
  are also used.
• Currently, the most widely used MS/MS has the
  configuration QQQ..

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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2006 Chapter 8 Tandem Mass Spectroscopy
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Advanced Analytical Chemistry CHM 6157 Y.
CAI Florida International UniversityUpdated on
10/9/2004 Chapter 8 Tandem Mass Spectroscopy