Agilent Technologies 7500 ICP-MS Operator's Manual page 108

Agilent 7500 ICP-MS ChemStation Operator's Manual
Tuning
Typical values for the ShieldTorch (Soft extraction mode)
Tuning parameter
RF Power (W)
Smpl Depth (mm)
Carrier Gas (L/min)
Makeup Gas (L/min)
PeriPump (rps)
Extract 1 (V)
Extract 2 (V)
Einzel 1,3 (V)
Einzel 2 (V)
Omega Bias (V)
Omega (+) (V)
Omega (-) (V)
QP Focus (V)
Plate Bias (V)
QP Bias (V)
4-32
Typical Range
∼
1500
1200 1600
∼
7
4 8
∼
1.15
0.8 1.3
∼
0
0 0.4
∼
0.2
0.06 0.20
∼
4
3 5
∼
-50
-60 -20
∼
-50
-100 -40
∼
10
0 15
∼
-35
-100 -25
∼
5
0 30
∼
0
-30 0
∼
3
0 10
∼
0
-10 0
∼
-10
-10 -5
In the Soft extraction mode, a higher plasma temperature setting
is necessary.
The Carrier gas flow rate and Sampling depth also affect the
plasma temperature. So it is necessary to adjust by combining
these three parameters.
If the Sampling depth is too great, it is the same effect as
increasing the RF power. For the correct effect, adjust the
Sampling depth and the RF power together.
However, making the sampling depth too small, may worsen
the oxide ion ratio and making the sampling depth too great
may cause a reduction in sensitivity.
When the Carrier gas is increased, it has the same effect of
decreasing the RF power. Adjust the Carrier gas and the RF
power together.
Set it higher to get a high sensitivity, but setting it too high
doesn't always increase sensitivity.
Even if the value of the Einzel lens is decreased, the
background may hardly be increased compared with the
standard torch. Only sensitivity may be increased.
Decreasing this value may increase sensitivity.
Even if the value of the Omega lens is decreased, the
background may hardly be increased compared with the
standard torch. Only sensitivity may be increased.
As ion energy is low, it is necessary to make the QP focus lower
than the standard torch. Make sure to use Positive voltage.
Using negative voltage will sharply increase the background.
As ion energy is low, it is necessary to add negative voltage.
Note