Tandem Mass Spectrometry: An arrangement of two or more mass spectrometers (tandem-in-space) or mass spectrometry experiments (tandem-in-time) placed one behind the other. Acronym: MS/MS; MS3; MSn
MS/MS Operation in QqTOF MS
RF-only mode
Product ions recording
Precursor ion selection
(From Chernushevich et al., JMS, 2001, 36, 849)
Quadrupole-Time-of-Flight (Q-TOF) Tandem Mass Spectrometer can be Viewed as:
• Ideal for obtaining product ion scan data.
Quadrupole-Time-of-Flight (Q-TOF) Tandem Mass Spectrometer
• First commercial Q-TOF mass spectrometer was introduced ~ 1996.
O
C
N
C
CH2
OH
N
CH2
CH
O
C
N
C
CH2
OH
N CH2
CH
O
+C C
CH2
OH
Байду номын сангаас
N CH2
CH
C
C
NH2
NH2
N
+
C+
C
NH2
NH2
N
NCNH2
C
NH2
N
CH2CH2O
m/z 196
O
C C
+C NH2
NH CH
N
m/z 110
O
CH2
OH
C
NH+ CH2
N
C
CH
C
C
NH2
NH
N
m/z 196
+ CH2
Low resolution/ unresolved isotopic peaks: Use average mass
Post Source Decay (PSD) Analysis Using a Reflectron
• PSD is a meta-stable decay process takes place after ions have exited source region.
• First commercial mass spectrometer that performed PSD analysis was introduced ~ 1994.
Post Source Decay (PSD) Analysis Using a Reflectron
(From Schematic Diagram of PE-SCIEX Voyager Elite MALDI-TOF mass spectrometer)
A+
fragmentation
product ions
A1+ , A2+ , A3+ , A4+
mass analyzer II
C+
I
D+
A+ B+
m/z
A2+ I A4+ A3+
A1+ A+
m/z
Activation (Dissociation, Fragmentation) Methods in MS/MS
• the replacement of the third quadrupole (Q3) in a triple quadrupole by a TOF mass spectrometer,
or
• the addition of a mass-resolving quadrupole and collision cell to an ESI-TOF.
O
CH2
OH
C
NH CH2
N
C
CH
C
C
NH
N
NH3
m/z 196
CH2CH2O
O
C
N
C
+C
C
NH
O
N C C NH2+ CH
C
C
NH2
NH
N
m/z 152
Product Ion
CH2
OH
N
CH2
CH
N
O
+C
N
C
C
C
NH
CH2
OH
N
CH2
CH N
CH2CH2O
O
C N
C NH
CH
C
+C
NH
N
m/z 135
• Parallel detection feature of TOF provides high sensitivity in full-scan mode.
• Most Q-TOF MS have reflectrons that provide high resolution and therefore high mass accuracy.
• Observation of PSD of MALDI ions was firstly reported in 1992 (Spengler et al., J Phys Chem, 96,
9678).
• It was realized that MALDI ions are not as soft as many had expected.
and post-translational modification analysis in proteomics study
Peptide Fragmentation Pattern Obtained by Product Ion Scan of Peptide Ion
772.913
Full MS scan
• Post source decay (PSD) analysis using a reflectron
• Quadrupole-time-of-flight (Q-TOF) tandem mass spectrometer
• Tandem time-of-flight (TOF/TOF) mass spectrometer
Mass analyzer
scan
Product ion scan (product of 772.9)
select ion collision-induced scan dissociation (CID)
Time-of-Flight (TOF)-Based Tandem Mass Spectrometers
• To increase selectivity and S/N ratio in quantitative measurement. For example, metabolite quatitation in complex biological matrices.
MS/MS by fragmentation enhances selectivity
Rationales for (Why) Performing Tandem Mass Spectrometry
• To obtain chemical structure-related information. For example, differentiation of isobar compounds or isomers.
OH
CH2
m/z 45
High Sensitivity and Specificity Provided by LC-MS/MS for N7-HEG Detection
Without matrix
Matrix effect considered
4 fmol
16 fmol
LC-MS/MS
LC-MS
LC-MS
128 fmol
1.02 pmol
Common Applications of Tandem Mass Spectrometry
• Examination of ion-molecule reactions • Molecular structural confirmation • Pharmacokinetic investigations • Neonatal screening for newborn diseases • Abused drug screening when LC-MS is used • Biological monitoring of toxicant exposure • Protein identification, de novo sequencing,
• Originally designed for ESI source, Q-TOF MS are also used with MALDI source now.
• Originally targeted for peptide analysis, Q-TOF MS are also applied to the analysis of small molecules such as pharmaceuticals and environmental toxicants.