Agilent Technologies 7500 ICP-MS Operator's Manual page 453

Agilent 7500 ICP-MS ChemStation Operator's Manual
Performing a Quantitative Analysis
2-2. Effective Example
Drift Change & Matrix Effect Dependence on Mass
Mass / amu
In this scatter plot Li6, Sc45, Y89, Rh103, In115, Tb159 and Bi209 show a clear
mass dependency. In such a case this virtual ISTD correction option is useful, in
particular some ISTDs are not available.
2-3. Limitation
It is important to note that space charge effects are not the only matrix effect. In
particular, a high matrix component in the sample is likely to lead to ionisation
suppression in the plasma, in which case the main component of the signal change
will be the analyte ionisation potential, not the analyte mass. If this is the case, then
mass-based interpolation of the internal standard signal will not necessarily improve
the data and a better approach would be to select internal standards that are close to
the analytes in terms of ionisation potential. If the relationship between the mass of
analytes and the sensitivity change is not consistent, the Virtual Internal Standard
correction option should be used with caution. The ISTDs behavior on mass axis can
be checked easily and, if necessary, you can make sure a further detailed check by a
recovery test.
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