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Function curve
. Opens a function curve-plotting window (polynomial,
δ
function, Lorenz
function, sine, sinc) with arbitrary parameters. For a polynomial, if there is an open curve, it
can be approximated with a polynomial of a given degree. The list also has the apodization
functions used in interferogram processing. If an interferogram is open before you run the
command, its center will be used to allocate the function correctly.
Calibration
You can use the program for calculating quantitative sample properties given individual
peak heights. The most often has to do with known contaminant concentrations in solutions.
Before measuring, you need to plot a calibration chart that shows the dependence of
concentration (or another property) on the selected peak height.
Plotting requires a set of spectra for samples with a known substance concentration.
As a rule, recording starts with the densest solution, which is later diluted multiple times and
recorded again. Continue diluting until the peak of the substance to be identify appears on
the spectrum. For greater accuracy we recommend that you repeat the entire procedure
several times starting over with a solution of the initial concentration.
Therefore, you get a few spectra. The concentration value should be specified in the
spectrum name or recording conditions (Fig. 9).
Figure 9. Calibration spectrum list
The program first checks there is a real number in the “conditions”; if yes, it is deemed
concentration; otherwise, the name is checked for the number. Repeating samples with the
same concentrations increases calibration precision.
Choose the peak to be used for calibration. This is usually a stand-alone peak pertaining
to the substance identified. E.g., an organic water contaminant analysis involves a 2870–
2900 cm
-1
C-H fluctuation range. Each spectrum is opened in turn. An absorption scale has to
be selected. Mark the peaks in the spectrum and point the cursor on the peak selected for
calibration. The peak will be highlighted with a red section at the base and a dashed cross
hair:
