Agilent Technologies 7500 ICP-MS Operator's Manual page 109

Agilent 7500 ICP-MS ChemStation Operator's Manual
Tuning
4 Adjust the torch position (Torch-H and Torch-V).
5 Adjust the flow rates of the Carrier gas and the Makeup gas.
6 Adjust the Peristaltic pump speed (Sample flow rate).
7 Adjust the RF power.
8 Adjust the Sampling depth.
9 Adjust the Ion lens parameter.
1) Adjust the Extraction lens.
Depending on the mass number of Li, Y, and Tl, the value for the highest sensitivity
differs. Therefore adjust the lens according to your purpose.
To reduce random background, increase the voltage of the Extraction lens 1 (about
+4.5V). Simultaneously adjust the Omega(+) voltage and Omega (-) voltage to
decrease Li and increase Y and Tl. Then make the sensitivity of Li several
Mcps/ppm. (If it's set integration time of 1ppb and 0.1seconds, it is equivalent to
several hundred count.). At this time, do not adjust the sensitivity of Y and Tl too
low. The guideline is more than 100Mcps/ppm. If checking the off mass
background on the tuning report, it is found that the background is restricted lower
than usual.
2) Adjust other lens parameters.
How to adjust the other lens parameters is almost the same as with the High
Sensitivity mode under the ShieldTorch.
Ensure not to set a too negative voltage when tuning for a reduced whole
background. As shown in the table, set -50 V instead of -100V to the Einzel 1,3, and
don't make the Omega bias lower than -35V. As for the Plate bias, it is necessary not
to make it too negative than necessary.
Adjust the Tuning parameter until signals are stable and high sensitivity is achieved.
The Following are examples of sensitivity:
4-33