Chromatography Forum

Hi All

We are analysing Erythromycin Estolate as per EP. During the analysis of the assay we can not get suitable chromatography with the reccommended column i.e "stationary phase: styrene-divinylbenzene copolymer R (8 µm) with a pore size of 100 nm" We are using a Phenomenex Polymerx column which is equivalent to the recommended column in the EP. After trying another type of column we found that a Waters Xterra C18 gave us much better chromatography. Are we allowed to use the Waters Xterra C18 column for the analysis of erythromycin?

Thanking you in advance
Michael Carolus

I notice the EP requires a colum temperature of 70C and the injection volume is 200ul. It may help to preheat the mobile phase.

There is a similar column from Polymer laboratories which may be better.

I doubt you could change column as the column is used for related substances. You would have to do work to show the equivalence of the 2 methods. ie you have to get the EP method to work before you can change it!

Are you sure your column is equivalent?.

The 2007 Phenomenex Catalogue shows PolymerX as being a 100A, not 100 nm?. That would be a very significant difference.

I don't yet have EP 6.0, but the EP knowledgebase notes that the column used for related substances was a PLRP-S, which I presume is the Polymer Labs range, and they offer both 1000A ( 100 nm ) and 100A ( 10nm ) products.

Polymer Labs are now owned by Varian, so the local agent should be able to confirm the correct column referenced by the EP.

Bruce Hamilton

Thanks for the advice. I will try to source the correct column.
Mike