Metrohm 761 Compact IC - Manual (Page 127)

4.4 Methods
761 Compact IC
117
4.4.5 Calibration and quantification
General information
The aim of any chromatographic analysis is to answer the question
"What components are present in the sample and what are their con-
centrations?". Two procedures are used to achieve this goal: the first
step is called calibration, the second step includes quantification.
Calibration has two aims: to get retention characteristics for all com-
ponents of interest (these data are stored in the component table) and
to establish a relation between injected amounts and corresponding in-
strumental responses for all components of interest (stored in the con-
centration table). Calibration is performed by running one or several
chromatograms of samples with known composition and known con-
centration of components (standards). For each calibrated component
a calibration curve is constructed as a result.
With the 761 Compact IC three different procedures can be used for the
construction of the calibration curve. By far the most important method
for ion chromatography is the external standard calibration (absolute
calibration) which is described in detail in this section. The other meth-
ods of internal standard calibration (relative calibration) and tabu-
lated calibration (relative gradient factor, a modified method for exter-
nal standard calibration) are of lesser importance and are not described
in detail here (for details please refer to on-line help).
Identification is a procedure that enables to decide what peaks on the
chromatogram correspond to what components. The identification is
performed on the basis of the Component table created for calibration.
Quantification is a calculation procedure that determines components
concentrations, on the basis of instrumental response (peak height or
area), using the calibration curves obtained earlier for each component.