Hi all,
I have a question about LC/MS of hydrofilic peptides.
Im working on small hydrofilic peptides in a C18 platform couple with an LCQ ion trapMS.
My mobile phases are H2O and ACN with 0.5 of formic acid respectively.
I begin the gradient with 5% of organic and the go to 100% of organic.
I put a hold time (5 minutes with 5% of organic to avoid the dwell time issues).
I cant see any signal from them ( concentrations are about 5pmoles on column).
I know that I will try to select other stationary( like SCX) phase but in the meantime have you any suggestions?
When I runned using the reodyne I can see them in the tune page of the mass spec ( good ionization ESI+) and I guess that is a chromatographic issue.
the sample diluent is 100% of water.

thanks a lot in advance