Problems with Polysorbate

[Bobbus]

Hi,

Can anyone help me out?

I am trying to develop a Reversed phase method but have Polysorbate and Potassium Sorbate present in the sample matrix (its a drug formulation). They elute right on top of some of my impurity peaks. I have tried playing around with selectivity and have tinkered with SPE but as yet have only had limited success. I am using a C18 phase and a low pH water MeCN gradient.

Any thoughts would be gratefully received

[g_wallace]

I recently had exactly the same problem.I solved it by using a phenyl hexyl phase.

[Bobbus]

Thanks g wallace

hmmm. Might have another look at that then. Did you resolve it from your peaks of interest?
I did have a phenyl hexyl in our column screen but went with a C18 as i was getting better selectivity around our main analyte. That decision was based on overall resolving power not specifically problems with the excipients. I will have a further investigate with the phenyl hexyl - cheers

These excipients seem to be in everything as preservatives so i am sure there must be a way to solve it.

I will try and post a chromatogram

[g_wallace]

Completely resolved them but we only had one peak of interest. We deal with polysorbate a lot, (formulation analysis), usually we just try to dilute those samples as much as possible. I guess if that's not possible you have to look at SPE or some kind of extraction.