Mixed mode
This integration method is a combination of the
methods
External standard
and
Area stand-
ardization
.
It takes into account unknown components and per-
mits response factors. This is in contrast to earlier:
the component list was previously deleted, and re-
sponse factor 1 used.
This integration method can be used to represent
the percentage distribution of the unknown compo-
nents in a sample.
Prerequisites for the calculation
Only peak areas are calculated, and not peak
heights.
The peak areas of known components are calculated
according to the external standard method with the
associated response factors. The components must
therefore be previously calibrated to percentage
values with an external standard.
Response factor 1 applies to unknown components.
Calculation
The percentage concentrations are initially calcu-
lated for those peaks which are entered in the com-
ponent list.
The total of these percentage values is subtracted
from 100. This results in the percentage of all un-
known peaks.
The percentage concentration of an unknown peak
is the ratio of its area to the area of all unknown
peaks times the percentage of all unknown peaks.
Special case
If, for any reason, the total of the known compo-
nents is 100 %, only the results of the known com-
ponents are displayed. This corresponds to the
method
External standard
.
Internal standard
(only laboratory version)
If an internal standard is used, an exactly known quan-
tity of a substance is added to the sample. The chroma-
tograph refers the concentrations of the other compo-
nents to this substance. The results are thus inde-
pendent of the injection accuracy.
Important: all components, including the internal stand-
ard, must first be calibrated once using the method
Ex-
ternal standard
so that the chromatograph can deter-
mine the calibration factors.
M
i
=
A
i
∗
K
i
A
s
∗
K
s
∗
M
s
M
p
∗
F
M
i
=
A
s
=
K
s
=
M
s
=
M
p
=
Concentration of component
Peak area of internal standard
Calibration factor of internal standard
Quantity of internal standard
Sample quantity without internal standard
The dimension of the result depends on how you enter
the two quantities. Example: internal standard in micro-
gram and sample in gram results in
ppm
.
NOTE:
If you enter zero for
Sample quantity
, the chromatograph does
not divide by zero! The concentration of the component is then
in the dimension which you have used for the internal stand-
ard. This method is only permissible if the sample quantity can
be exactly reproduced.
Integration
14
5AUSWERT.CHP, Stand Dezember 22, 1999
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