dn/dc Measurement

The differential refractive index dn/dc quantifies the change of refractive index of a solution with concentration of the analyte. There are at least three reasons for measuring dn/dc of a polymer sample:

In order to use a differential refractometer to measure concentration online with GPC – dn/dc represents the instrument response

Analysis of MALS data requires knowledge of dn/dc at the MALS wavelength

The fraction of each monomer in a co-polymer solution can be estimated if the dn/dc values of the two monomers differ significantly

Manual measurements of dn/dc are readily carried out on the Optilab differential refractometer by means of the WISH™ Injection Module. Automated measurements may be carried out by combining the Optilab with a Calypso composition-gradient system.