Static measurements of refractive index increments at 633 nm with a modified refractive index detector

Summary A R 401 Waters Assoc. differential refractometer has been modified to obtain the variation of refractive index increments, dn/dc, of polymer solutions at 633 nm. The introduced modifications were in the sample injection system and in the light source. The performance of the modified refractometer both with aqueous and organic solutions is analyzed. In order to localize a conformational transition in lysozyme, the dependence of dn/dc on temperature for lysozyme solutions in phosphate buffer is studied. Similarly, (dn/dc)_k values for the ternary n-alkane/butanone/poly(dimethyl siloxane) systems over the whole composition range of the binary solvent mixtures are evaluated.