Using Internal Standard Correction; Auto Add Mode - Agilent Technologies 7500 ICP-MS Operator's Manual

Agilent 7500 ICP-MS ChemStation Operator's Manual
Performing a Semiquantitative Analysis

Using Internal Standard Correction

ChemStation enables you to make internal standard corrections if you add internal
standards to your sample in known concentrations. In semiquantitative analysis,
internal standard correction is strongly recommended, since changes in sample
matrix can effect instrument sensitivity, which will directly affect the reported
concentration values.
There are two modes of internal standard addition: Auto Add Mode and Normal
Mode. The settings are not saved when you change between modes.

Auto Add Mode

The Auto Add Mode is used when the internal standard is added automatically with
a peristaltic pump (on-line ISTD addition). In this case, the precise internal standard
(ISTD) concentration may not be known, but the ISTD concentration in every type
of sample - calibration standard, a blank, an unknown sample, etc. - will be
identical.
The internal standard factor is calculated using the following equation:
ISTD factor = (cps of ISTD in the Internal Standard Data File)
The concentration for each element is calculated using the following equation:
Conc. = (cps in sample) x (ISTD factor) x (dilution factor)
where the dilution factor is obtained from the Start Run panel if running a
method or in the Sample Log Table if running a sequence (default = 1.0); and the
SemiQuant factor is obtained from the SemiQuant parameters panel.
To set up the Internal Standard Correction, perform the following steps in Data
Analysis:
/ (cps of ISTD in the sample)
/ (SemiQuant factor)
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