Waters
Triple Quad Mass Spectrometer
Q0
RF only
Q1
Scanning
RF/DC
Q2
RF only
Collision Cell
Q3
Scanning
RF/DC
• Q1 and Q3 are standard mass filter quadrupoles.
– The can scan masses sequentially (e.g. 50 to 500 amu)
– The can be used to select a single mass.
• Q2 is an RF only quadrupole that is in a gas filled
chamber.
– Q2 is the “collision cell” where mass fragmentation occurs.
– Q2 does not filter ions. It accepts all ion sent to it by Q1
and passes all ions formed by collision to Q3 to be sorted.
(Triple Quadrupole)
Tandem-in-Space vs.
Tandem-in-Time
(Quadrupole Ion Trap)
triple
GC/triple
Triple quad modes of operation
Triple Quads…
• In scanning mode 99% ions lost between the rods.
– Poorer full scan sensitivity
• In SIM mode 100% of selected ion reaches detector.
– Makes them highly sensitive and great for
quantitation!
• Mass resolution typically limited to “unit” (+/- 0.2 amu)
• Fragmentation is controlled by the energy ions have
when they enter the collision cell.
– Higher energy >> greater fragmentation.
Hybrid Instruments
Applied Biosystems 3200 Qtrap System
Q0
Q1
Q2
Q3
• Typically in the same configuration as a
triple quadrupole instrument.
• On the Qtrap Q3 is the hybrid quadrupole
dubbed a “linear ion trap” or LIT.
• Q3 can function as a quadrupole OR an
LIT.
Main RF
Ramped…
LIT Scanning
Radial Trapping
…simultaneously
Ramp EXB
Axial
Trapping
Q2
Auxiliary RF
Ramped….
Radial Trapping
Exit Lens
with Grid
Advantages of LIT vs. IT
• Has a larger “volume” so it can be filled with more ions
before exhibiting space charge effects.
• Ions are formed outside the trap, so it is not limited by
the 1/3 rule.
• Can perform MS/MS/MS experiments by selecting an ion
and fragmenting it using the spillover collision gas. (1/3
rule applies here…)
Modes of Operation
• Triple Quads and Ion Traps
– Full Scan (LC/MS)
– MRM (Multiple Reaction Monitoring)
– Product Ion Scan (PI)
• Exclusively Triple Quad
– Constant Neutral Loss
– Precursor Ion Scan
• Exclusively Ion Trap
– MSn
H
Y
B
R
I
D
S
Multiple Reaction Monitoring
(MRM)
Steps MS2:
1
2
3 &4 Exit lens
Ion accumulation
Q0
Q1
Precursor ion
selection
Q2
Q3
Fragmentation
N2 CAD Gas
• Q1 Selects an [M+H]+
• Q2 fragments the selected ion.
• Q3 monitors only one daughter ion
MRM
Steps MS2:
1
2
3 &4
Exit lens
Ion accumulation
Q0
Q1
Precursor ion
selection
Q2
Q3
Fragmentation
N2 CAD Gas
• Only the daughter ion reaches the detector.
• Sensitivity of MRM is a function of how much of
the daughter ion is produced.
• The parent ion fragmentation to daughter ion is
commonly referred to as a “transition”
Example MRM Data
Oxycodone: (316.2Æ241)
Parent : 316.2
Daughter : 241
Result of one MRM cycle of 130 drugs.
• Many transitions can be stacked together in a method.
• The instrument will monitor each pair for a short time.
• MRM is analogous to SIM on a GC/MS only more
compound specific.
Product Ion Scanning
Steps MS2:
1
3 &4 Exit lens
2
Ion accumulation
Q0
Q1
Precursor ion
selection
Q2
Q3
Fragmentation
N2 CAD Gas
linear ion trap
3x10-5 Torr
• Q1 selects a parent ion.
• Q2 fragments the selected ion
• Q3 traps then scans out all fragment ions.
Product Ion Scan
Steps MS2:
1
3 &4 Exit lens
2
Ion accumulation
Q0
Q1
Precursor ion
selection
Q2
Q3
Fragmentation
N2 CAD Gas
linear ion trap
3x10-5 Torr
• Selection of a single parent ion by Q1
allows separate product ion scans for
coeluting compounds to be easily
generated.
– Provided they don’t have the same mass…
Example EPI Data
• Oxycodone (316.2) is selected by Q1.
• Q2 fragments oxycodone
• Q3 operating as an LIT traps all the
fragments, and the scans them out.
• “Enhanced” means using the LIT.
Linking MRM and EPI
• MRM is an excellent survey method.
– Allows for stacking of many transitions
– Relatively fast* cycle time
• EPI is an excellent for qualitative identification
– Parent ion linked fragmentation pattern
– Many fragments that can be library matched.
• An ideal qualitative method would use MRM to look for
drugs, and EPI to confirm them.
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