Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Specific refractive index increment (dn/dc) of polymers at 660 nm and 690 nm



Andre M. Striegel


The specific refractive index increment (dn/dc) is an essential datum for the accurate quantitation of molar mass averages and distributions (inter alia) of macromolecules when refractometry, static light scattering, and/or viscometry detection are coupled on-line to size-based separation techniques. The latter include methods such as size-exclusion and hydrodynamic chromatography, and asymmetric and hollow-fiber flow field-flow fractionation. The dn/dc is also needed for accurate determination of the weight-average molar mass of polymers by off-line, batch-mode multi-angle static light scattering. However, not only does dn/dc differ among chemical species, it also depends on experimental conditions such as solvent, temperature, and wavelength. For the last seventeen years, the author’s laboratories have measured the dn/dc of a variety of natural and synthetic polymers, at both 690 nm and, more recently, 660 nm, under a variety of solvent and temperature conditions. In all cases, this has been done by off-line, batch-mode differential refractometry, not by assuming 100% analyte column recovery and 100% accurate peak integration. Results of these determinations are presented here, along with the relevant experimental data.


Specific refractive index increment, dn/dc, polymers, refractometry, light scattering, size- exclusion chromatography, hydrodynamic chromatography, field-flow fractionation


Striegel, A. (2017), Specific refractive index increment (dn/dc) of polymers at 660 nm and 690 nm, Chromatographia, [online], (Accessed June 22, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created June 1, 2017, Updated November 10, 2018