The 1260 Infinity Mds Refractive Index Detector; Measurement Principle And Light Path - Agilent Technologies 1260 Infinity User Manual

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Appendix 1– Theory of Operation

The 1260 Infinity MDS Refractive Index Detector

The 1260 Infinity MDS Refractive Index Detector

The MDS differential refractive index detector is a high performance
device specifically designed for GPC. The RI detector features high
signal- to- noise and low levels of drift and is fitted with a low dispersion
cell to maintain peak shapes throughout the sample injection. The heated
cell environment means that excellent temperature stability is maintained,
giving ultra stable baselines.

Measurement Principle and Light Path

A light beam emitted from an LED crosses the sample and the reference
cell of the RI detector twice. When both cells contain pure solvent, the
system is calibrated to zero by means of a parallel zero- plate that
positions the beam on the two detector diodes 1 and 2 in such a manner
that the measured light intensities (I
virtually identical. When the sample cell contains a solution with a
different refractive index to that of the solvent, the light beam is
geometrically proportionally deflected depending on the relative change of
the refractive index (according to Snell's refraction law).
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and I ) of the two diodes are
1 2
Agilent MDS User Manual