The EDIT-CHANNELS–
COMPONENTS-DETAILS Screen
(continued)
Peak Number, Peak Name, Start and End
A blank Component Details screen is
opened by selecting the Add button. Enter a
unique Peak Number for each component,
typically starting with 1 and incrementing for
each additional peak. Then enter a unique
Peak Name for each component. Start and
End define the beginning and ending of the
retention windows, which is used to identify
the peak. The width of the retention window
should be set wide enough so that small fluc–
tuations in the peak's retention time will still al–
low for proper integration.
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The internal standard calculation
yields a result which is the external result
times the ratio of the known concentra–
tion of the internal standard peak di–
vided by the external result for the in–
ternal standard peak. As shown in the
example to the right, note that while the
external result for Benzene yields 104.95,
the internal result yields exactly 100 (the
known concentration) as a result of the
calculation 104.95 x 100/104.95. In the
same way, the internal result for every
analyle peak which is referenced to Ben–
zene is calculated as external result x
100/104.95
=
internal standard result.
Internal Standard calculations are used to correct for injection size variations, or
to compensate for changes in detector sensitivity. An internal standard peak is added
to the sample prior to injection at a known concentration. The internal standard peak
is calculated just like any other peak using a calibration curve, typically a single point
calibration. The known concentration of the internal standard peak is entered into the
Internal Standard dialog box of the Component Details screen. In the example
shown below, Benzene has been chosen as the internal standard peak. The known
concentration of Benzene is entered as 100, and ppm is entered in the Units dialog
box. When a chromatogram is integrated and a report is produced, the external calcu–
lation yields a result which is the peak area x calibration factor (slope of the calibra–
tion curve)
=
external standard result.
