Jasco RI-2031, Инструкция по эксплуатации

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10. Appendix
10.1 Operation Theory
10.1.1 Operation theory of deflection differential refractometers
With deflection differential refractometers, light refracted inside the prism flow
cell is used to detect the difference in refractive indices between the reference
(solvent) and the sample.
The flow cell structure and light path are shown in Figure 10.1.
i
n
n
S
R
i
θ
r
Figure 10.1 Horizontal Cross-section of Flow Cell and Light Path
The area to the left of the center partition is called the sample cell and the area
to the right is called the reference cell.
n
s
: Refractive index of sample
n
R
: Refractive index of reference (solvent)
θ
: Angle of deflection (exaggerated in the figure: actual value is <10
-2
degree.)
i: Angle of partition (determined by cell shape)
Applying the law of refraction to this light path and assuming
θ
<< 1 (since the
actual value is 10
-2
or less),
θ
can be expressed as follows:
θ
= tan i x(n
S
-n
R
)/n
R
... (1)
From this equation, the angle of deflection is proportional to the difference in
refractive indices between the reference solvent and the sample. In other
words, it is possible to determine the difference in refractive indices between
the reference solvent and sample by measuring the angle of deflection.