Chromatography Forum

I am trying trying to quantitate ethylcellulose in a mixture of ethylcellulose (EC), PVP and active (small molecule). By size-exclusion there is no problem in separating PVP and EC from the low molecular weight components. However, it seems almost impossible to separate PVP and EC. That makes RI detection not a good choice.

There is almost no UV absorbance of either EC and PVP. Do anyone know a good derivatisation of EC that will give it a better UV signal (and not affect the PVP)?? That is the only thing I can think of right now. Can benzoic acid anhydride react with the OH groups in the cellulose?

Thanks!

Hi again!

Back to the basic question Has anyone ever tried to quantitate ethylcellulose with HPLC?

I have a mixture of polyvidone and ethylcellulose, and it seems impossible to separate them on SEC.

If you tell us what PVP is, the molecular weights involved, and optimum weight separation (useable mw range) of the column we might venture a stab at this.

PVP is polyvinylpyrrolidone, aka povidone.

I have worked with –cellulose and Povidone (PVP), so let me give it a shot.
Povidone (PVP) has a strong UV absorbance in the lower wavelength (195-220 nm). Ethylcellulose (EC) may not absorb in this region (please confirm this by doing an UV scan of a 0.2-0.5% solution-we don’t have this material). So, detection for EC will be by RI, and PVP by UV.
Separation may be a challenge, because PVP has a rather broad MW distribution, and this distribution depends on the K-value. You may need to couple two SEC columns to separate PVP and EC. For lowest cost, check the PolySEP GFC columns from Phenomenex.
Perhaps you may not need to resolve PVP and EC to quantify them?
Note: I am not related anyway to Phenomenex.
Alfred

With only Alfred´s hint at the mw I will try a long shot: Just a guess actually. Both polymer types probably dissolve in H2O, and the cellulose derivative may react with base more readily than the pyrrolidone...? If so, how about ion chromatography?

Its likely to be very challenging indeed to separate your 2 polymer components by GPC if the MW distributions are wide and of comparrable MW. A selective detection method coupled to GPC would be a way to go. FTIR is available and you may be able to pick out IR signals specific to one component.

How about Gradient Polymer Elutions Chromatography (GPEC). This may separate the 2 in a solvent/non-solvent gradient LC run.