resolution between impurities "official" requireme

[ricopalazo]

Hi all,
I'm looking for some informations about the autorities requirement for the resolution between impurities (very low concentration, ~0.1-0.5% area) on a peptidic purity profil.
A "good" resolution between peaks is theorically >= 1.5.
But with a peptidic pharmaceutical product, it's difficult to obtain this resolution for all the peaks detected (above LOD, with an optimized method).

Do you have any information/reference that can give what the autorities (FDA,...) will expect?
Is the requirement for HPLC and UPLC the same?

Thanks a lot

Rico

[grzesiek]

Why there should be one anyway? Nobody's interested in resolution between peaks but us chromatographers

[Alex Buske]

UPLC is not cited in official pharmacopoeias or guidelines.

[tom jupille]

Several comments:

First of all, "UPLC", "UHPLC" (and "HPLC", for that matter) are marketing buzz-acronyms. It's all "liquid chromatography".

Second, you have to recognize that the "1.5" definition of baseline resolution was originally referred to as "99% baseline resolution". Over the years, the "99%" has fallen from use, but the original definition remains: it's the resolution at which there is just less than 1% overlap between two equal-sized Gaussian peaks. That kind of resolution is adequate for comparable-sized peaks (assuming the tailing is not too bad!), but it is grossly inadequate for a small impurity next to a large parent peak.

Third, the US FDA suggests (not requires!) that resolution should be >2.

Finally, if you can demonstrate acceptable precision and accuracy when you validate the method, then whatever resolution you had was adequate for the purpose. You write that in (with some safety margin) to the system suitability requirements.

Bottom line, don't worry so much about requirements as about making the analysis work (and demonstrating that it *does* work!).