Generating A Calibration Curve - Agilent Technologies 7500 ICP-MS Operator's Manual

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

Generating a Calibration Curve

ChemStation uses calibration curves to calculate analyte concentrations in unknown
samples. You set up calibration curves using the data files ChemStation generated
after analyzing calibration standards.
The calibration curve created in an External Calibration method is based on
calibration standards which have been prepared by spiking one or more elements of
known concentrations into a clean matrix, such as acidified water. In contrast, the
calibration curve created in a Standard Addition method is based on calibration
standards prepared by spiking aliquots of the unknown sample with known
concentrations of the elements of interest.
The descriptions provided in this section are for setting up an External Calibration
curve. Any differences between setting up an External Calibration curve and a
Standard Addition curve will be noted where appropriate.
This section explains how to create a calibration curve by performing the following
functions: setting up calibration files, calculating calibration concentration levels
and selecting calibration equations. Finally, this section explains how to view
calibration curves and determine if they are acceptable.
If the calibration curves are not acceptable, you can exclude points from the curves;
this might be necessary if, for example, one of the standards was found to be
incorrectly prepared. You can also add points to the curve by running additional
calibration standards and rechecking the calibration curves before you continue.
Setting a background file allows the user to subtract background counts from any
data file. This subtracts the raw counts before calculation; the abundance for each
mass acquired in the background file are subtracted from the abundance of the
corresponding mass in non-background file. Background subtraction (or
background correction) should not be confused with blank concentration subtraction
which is performed after concentrations have been calculated and is used to subtract
the reagent blank from an unknown sample. Background correction should NOT be
used in a quantitative analysis using an internal standard because the internal
standard element counts will be subtracted from the non-background file.
(The background file and interference correction can be set at Method>>Data
Correction in the ICP-MS Data Analysis window).
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