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Agilent 7500 ICP-MS ChemStation Operator’s Manual
Performing a Semiquantitative Analysis
Changing the Mass to be Analyzed
In normal circumstances, the default masses displayed in the SemiQuant Parameters
window are the best choices, so there is no need to change them. However, there
may be cases when you want to change the default mass; for example, to see the
difference in using alternate mass, or in the event that the sample matrix gives rise to
a polyatomic ion that would interfere with the default analyte mass.
To change the default mass, complete the following steps:
1 Click the mass you want to change.
A text box and an Enter button appear at the bottom of the dialog box.
M/Z Text Box
NOTE The original response factor listed in the SemiQuant Parameters panel for a given
element was determined based on the default mass for that element. If the mass is
changed to a different isotope, the response value is not automatically changed to
reflect the different relative abundance of the alternate isotope. Therefore, if it is
necessary to change the mass, a new response value must be entered. The new
response value can be calculated by correcting the original response value for the
relative isotopic abundance difference between the default mass and the alternate
mass. For example, the default mass for Cu is 63; the default response value for Cu
is 8123. If it was necessary to measure Cu using mass 65 rather than 63, the new
response value would be calculated as follows:
x = [(rel. abn. Cu65)/(rel. abn. Cu63)] * orig response value for Cu
= [(30.8)/(69.2)] * 8123
= 3615
Relative isotopic abundances can be taken from the Relative Isotopic Abundance
Table laminated card provided with your Agilent 7500.
2 Type in the new mass and response value and click Enter.
The changed value appears for the selected element.
NOTE Default masses are chosen so as to avoid isobaric and common polyatomic overlaps.
Where there are several interference free isotopes, then the most abundant is selected.
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