Chromatography Forum

Dear Experts,
I am developing methods for the analysis of topical formulations such as creams and currently troches. The Progesterone troche has a polyethylene glycol (MW1500) base and I need to extract the Progesterone from the troche. I have a method from USP25 for progesterone suppositories (PEG) which I am going to use. My worry is the potential fouling of my columns with the constituents of these applications. As per the method I am using mobile phase (H2O:ROH) (45:55) where ROH = Ethanol:2-Propanol:Methanol (90:5:5) to extract the active from the troche. Is there any way I can be sure that the PEG will not foul the column(C18)?
regards
Martina

Martina,
There are two approaches to the PEG problem. One is to try to keep it off the column in the first place. You could try a SPE method to isolate your analyte and then proceed with your analysis. Two would be to clean up your column after the analysis is complete. A high concentration of Methanol should wash the PEG off the column.

PEG is very weakly retained on reversed-phase columns. With a MW of 1500 it is sufficiently soluble in your mobile phase that there will be no serious issues. Just use a good membrane filter to keep insoluble matter out of the column. If there are oils, greases, surfactants, or emulsifiers in the formulation, that is a different story.