Hitachi PRIMAIDE 1440 Instruction Manual page 42

(3) Second-order and Third-order Radiation
The Raman peak is described as a cautionary item when
the excitation and emission wavelengths are comparatively
close to each other. Conversely, when these wavelengths
are comparatively distant from each other, the analyst
should be aware of the second and third-order radiation
phenomenon.
The second-order radiation occurs at a double wavelength
of the excitation beam and the third-order radiation arises at
a triple wavelength.
For instance, if the excitation wavelength is 240 nm, the
second-order and third-order excitation occur at 480 and
720 nm, respectively. To eliminate second and third order
radiation, it is simply necessary to place a short-wavelength
cutoff filter in the path of fluorescing radiation.
When the second and/or third-order radiation poses a
particular problem, it is recommended to use the optional
filter set accessory.
In measurement with a chromatograph, the second and
third-order radiation appears as a background rise.
Therefore, baseline noise will increase to disturb high-
sensitivity measurement.
(4) An Example of a Fluorescence Spectrum
Figure 3-10 provides an example of a fluorescence
spectrum.
1)
2)
EX
1) Scattering of excitation beam
2) Raman scattering due to mobile phase
3) Fluorescence of impurity
4) Fluorescence of compound of interest
5) Second-order scattering of excitation beam
Fig. 2-10 Measurement Example of Fluorescence Spectrum
3)
2 - 14
5)
4)
EX  2
Wavelength