Agilent Technologies 7500 ICP-MS Operator's Manual page 120

C A U T I O N
Agilent 7500 ICP-MS ChemStation Operator's Manual
Tuning
• Makeup Gas
Makes up Ar gas into the spray chamber and is mixed with the carrier gas. When
the Ar gas supply pressure is not high enough to get a sufficient carrier gas flow,
the makeup gas is used.
• Optional Gas (option)
When the optional gas line is added, it is possible to introduce a gas other than
argon. (e.g. introduction of oxygen etc. when measuring organic solvent)
• PeriPump 1
Controls a sample uptake rate and the drain from the spray chamber. It affects
sensitivity, stability of signal, and oxide and doubly charged formation. Higher
speed increases sensitivity, but too high speed, decreases sensitivity. Higher
speed increases oxide and doubly charged ions.
Even when self-aspiration is used for sampling, the PeriPump 1 must be operated to
drain the sample from the spray chamber, if this is not optimized the spray chamber
will fill with sample solution.
• PeriPump 2 (option)
It can be used when a second (optional) peristaltic pump is installed on the
ICP-MS. It is possible to shorten the rinse time or the sample uptake time.
• S/C Temp
Controls the temperature of the spray chamber. Lowering the spray chamber
temperature causes the sample vapor temperature to lower and removes more
water, thus, reducing the oxide levels. It should be set at 2 ºC for aqueous sample
to avoid ice formation. When aspirating organic solvents run the chamber at -5
ºC.
Ion Lens
• Extract 1
It extracts ions from the plasma to accelerate them toward the Einzel lens. Adjust
to get enough sensitivity for all masses. This is lens that needs the most
frequently adjusted everyday.
In order to get maximum sensitivity, adjust between 4 V and 8 V. An element of
low mass gets maximum sensitivity at low voltage. On the other hand, an
element of high mass number gets maximum sensitivity at high voltage.
Therefore, select the appropriate voltage. Even with the voltage around -100V,
high sensitivity can be obtained. However, the background of polyatomic ions
may be high in reaction mode (H
4-44
mode or He mode)
2