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Problem Possible
Cause
Solution
The baseline of the spectrum is
not flat.
A poorly prepared KBr pellet (disc)
scattered the light and caused a
sloping baseline.
Use fresh, dry spectroscopic
grade KBr, appropriately ground
and well mixed with the sample.
The background spectrum for a cast
film was collected through an empty
sample holder.
Collect a background spectrum
with a clean substrate in the
infrared beam. Use the same
substrate (material and thickness)
as used for the base of the cast
film.
The spectrometer is not properly
aligned, causing a sloped baseline.
Use the Align button on the
Diagnostic tab of the Experiment
Setup dialog box to align the
spectrometer.
The spectrometer has not been on
long enough to reach thermal
equilibrium.
For best results allow the
spectrometer at least one hour to
stabilize after turning it on.
Remove the sample holder and
collect the background again.
The spectrometer is not properly
purged.
Check the system to make sure
the correct purge gas is being
used and that the flow rate is
correct.
A spectrum is too noisy.
There were too few scans.
Increase the number of scans on
the Collect tab of the Experiment
Setup dialog box.
The purge gas flow rate or pressure
is too high.
Check the pressure regulator; it
should be set between 0.7 and
1.4 bar (70 and 140 kPa, or 10
and 20 psig). Check the
flowmeter; it should read 15 scfh
(about 0.4 m
3
/hr). Adjust the flow
rate if necessary.
continued…
Thermo Electron Corporation
120
Summary of Contents for Nicolet 380
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