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3.3.1. Use at high temperature
Figure 12: Probe is heated causing the spectrum to tilt
In Figure 12, the spectrum is tilted, with positive absorbance at lower wavenumbers and
negative absorbance at high wavenumbers and the spectrum is not flat in the region 800-
1800cm
-1
. This indicates that the probe tip is at a higher temperature now than it was when
the background was taken. This may cause chemometric models to give incorrect results
unless the model uses an appropriate pre-treatment to remove the effect. Any model built by
Keit will have this taken into account.
3.3.2. Emitter ageing
Figure 13: Spectrum is tilted showing signs of emitter ageing
The infrared emitter in the probe is expected to age over its lifetime. The results of this can be
seen in Figure 13: the spectrum is tilted; the absorbance is positive across the whole spectrum;
and the spectrum is not flat in the region 800-1800 cm
-1
(contrast with Figure 7, above). If
evidence of emitter ageing is seen, it may be required to take a new background scan to
remove this effect
– contact Keit for advice.
