Hardware manual

Overview 1
Agilent 7500 Series ICP-MS Hardware Manual 1-15
ICP Source
The fine sample aerosol that exits the spray chamber passes directly into the
injector tube of the horizontally mounted ICP torch. The ICP torch is
comprised of three concentric quartz tubes through which streams of argon
pass (Figure 10). These three gas streams are referred to as the plasma gas,
auxiliary gas and nebulizer (carrier) gas.
Figure 10 ICP Torch and Load Coil
The end of the torch is situated inside the 4- turn work coil, through which a
radio frequency (RF) current oscillating at 27.12 megahertz (MHz) is passed.
After seeding the plasma with electrons, collisions of Ar atoms in the intense
RF field generates and sustains an argon plasma.
In the center of the plasma, temperatures range from 8,000 to 10,000 Kelvin
(K). The sample aerosol is instantaneously desolvated and ionized. The Argon
plasma is a good source of singly charged positive ions allowing most of the
elements of interest to be ionized with an efficiency of greater than 90 percent.
All the Argon gas and optional gas supplies are mass flow controlled. This
contributes to very good signal stability.
The carrier gas flows through the innermost tube called the injector tube and
delivers the sample aerosol to the plasma.
The make- up gas line is used for adding make- up gas when using the
ShieldTorch interface (cool plasma).
An optional gas mass flow controller (if installed) allows for the addition of
mixed carrier gases to the plasma. This can be useful for certain applications.
For example, the addition of O
2
reduces carbon build- up on the interface
when analyzing organic solvents.
Auxiliary
Carrier
Auxiliary
Plasma Gas
RF Coil
(
Cooled
)
RF Filed
RF Filed