Feature Of The Shieldtorch System; Effect Of Carrier Gas Flow Rate - Agilent Technologies 7500 ICP-MS Operator's Manual

Agilent 7500 ICP-MS ChemStation Operator's Manual
Tuning

Feature of the ShieldTorch system

There is a clear difference between the standard system (without the ShieldTorch)
and the ShieldTorch system. Each has advantages and disadvantages, therefore it
must be considered which system is better for the samples and elements to be
analyzed.

Effect of Carrier Gas Flow Rate

Standard system
• The optimal carrier gas flow rate, which gives the maximum sensitivity for
analytes depends on the mass; the optimum flow rate for heavier elements is
lower than that for lighter elements.
• The signals of polyatomic ions such as ArH, ArO, ArAr, and CO
carrier gas flow rates higher than the optimum flow rate, and then gradually
decrease.
• The behavior of Ba
increasing the carrier gas flow increases the ratio of Ba
BaOH/Ba.
Increasing the carrier gas flow reduces the residence time of analytes in the plasma,
which leads to insufficient decomposition. The elements that form a strong bond
with oxygen, such as Ba and REEs (Rare Earth Elements), form oxides, some of
which can be ionized as oxide ions.
The ShieldTorch system (Cool plasma)
The optimal carrier gas flow rate, which gives the maximum sensitivity for analytes
depends on ionization potential, boiling point and bond strength. The optimal
carrier gas flow rates are different for Be and Li because of ionization potential, or
Pb and W because of boiling point and the bond strength with oxygen, even though
the mass numbers are close. In contrast, Co, In, and Pb show similar behavior,
despite having very different masses.
• The signal of ArO drastically decreases as a function of higher carrier gas flow.
The signal of ArH also drastically reduces at first, and then gradually increases.
The behavior of Ar is almost the same as that of ArH.
• Levels of BaO and BaOH increase (especially, BaOH) at higher carrier gas flow
4-22
2+
, BaO, and BaOH is similar to the polyatomic ions;
increase with
2
2+
/Ba, BaO/Ba, and