PlasmaQuant MS product family
Function and setup of the PlasmaQuant MS
27
At this pressure, ions can be guided by ion optics. Neutral gas atoms, molecules and
photons, on the other hand, diffuse into the vacuum chamber and are pumped away.
The final stage of the vacuum system, containing the mass analyzer and the detector,
is maintained at a pressure of around 7 x 10
-5
mbar by a second turbomolecular pump.
In the plasma, not only analyte ions are formed. The plasma gas Argon as well as
matrix components (e.g. O, Cl) form positively charged ions in large amounts. They
interfere with analytes having the same mass-to charge ratio and thus precluding their
detection.
Summary 1
Common elements and Interferences
Analyte
Interferences
40
Ca
40
Ar
51
V
35
Cl
16
O
52
Cr
40
Ar
12
C,
35
Cl
16
O
1
H,
36
Ar
16
O
53
Cr
40
Ar
13
C,
37
Cl
16
O
56
Fe
40
Ar
16
O,
40
Ca
16
O
75
As
40
Ar
35
Cl
78
Se
40
Ar
38
Ar
80
Se
40
Ar
40
Ar
The iCRC is patented technology, superior to known Collision Cells. The iCRC removes
interfering ions before they reach the mass analyzer by introducing gases (hydrogen or
helium) into the plasma as it passes through the skimmer cone. Hydrogen eliminates
interfering ions by reacting with them. There is no secondary chemistry found. The by-
products of the reaction are neutrals and H
+
-Ions, which is harmless.
Furthermore the iCRC gases cause all the ions to slow down, as the ions collide with
the gas particles in their path. Interfering polyatomic ions are larger than the analyte
ions. Hence, the polyatomic ions collide with helium atoms, more often, and reduce
their speed stronger. They can be excluded from the mass analyzer by Kinetic Energy
Discrimination realized in the ion optics. With the iCRC the signal-to-background ratio
is improved ensuring lower detection limits.
BOOST control: By applying positive voltages to the skimmer cone, ions are focused at
the exit of the interface, thus improving sensitivity.
Fig. 11 Relative size distinction between polyatomic and analyte ion
The iCRC (integrated
Collision Reaction Cell)