Chromatography Forum

Hi All,

Currently we are in process for development of Stability indicating LC method for a peptide type of drug. The molecular weight is around 1500. On YMC columns it shows good peak shape and over a period of time gives tailing. The mobile phase used if 0.05%TFA in water and Acetonitrile in gradient.

Can any one suggest a possible isocratic method for the molecule?

Thanks,

Yogesh

Can any one suggest a possible isocratic method for the molecule?

Depends on how wide a spread of retention you have for degradants. Peptides tend to have fairly high S-values (S is the slope of a plot of log(k') vs fraction strong solvent), which means that retention changes a lot for small changes in composition. This means that it's difficult to get much of a range of peptides in a single isocratic chromatogram, and it means that retention time can vary considerably with small errors in mobile phase composition.

That said, if you really want to try isocratic, look at the %B when your peptide comes off the column and try about 3% lower as a first shot. Adjust as necessary from there.