Chromatography Forum

Can anybody help me in finding the dn/dc value of PMMA standard in DMF. I found this Polymer Handbook by Brandrup/Immergut, and found the dn/dc value as 0.060 on page VII 570 at 436 Wavelength but don't have resources to get the literature or reference of that dn/dc value. If anybody is polymer expertise, than please guide me!
Thanks

The refractive index difference between PMMA and DMF 0.0608 at 589 nm (sodium line)
It's a little more than 0.07 at 436. What kind of light does your RID use?
And what is dn/dc? Is that change in RI vs concentration?

Thanks for the reply! what do you mean by sodium line? And where it is documented? i calculated the dn/dc value
(difference refractive index of PMMA with the refractive index of the DMF. But I was told that it must be documented in some literature. I have a GPC instrument from Wyatt and the Optilex detector uses the Light scattering at the wavelength of 585 nm. And yes dn/dc is the change in RI vs concentration. i found on the net this defination of dn/dc
as follow: please let me know.

thanks once again

dn/dc has the units of mL/g since refractive index, n, is a pure number. We can also guess that dn/dc is generally a small number. For example, poly(methylmeth- acrylate) has a refractive indexes in its pure state of about 1.5 and a density of about 1 g/mL. The refractive index of a typical solvent (say, THF) is about 1.4. A ballpark figure for dn/dc is, therefore, (1.5-1.4)/(1 g-mL-1)  0.1 mL/g.

Hi Sepscientologist,

You wrote: {The refractive index difference between PMMA and DMF 0.0608 at 589 nm (sodium line)}
where it is documented??? please let me know!


thanks