A common mobile phase for RPC of peptides can be, for example, a gradient of 0.1% trifluoroacetic acid (TFA) in water to 0.1% TFA in an organic solvent, such as acetonitrile, since the organic solvent 1) solubilizes the protein or peptide, 2) allows detection at approximately 230-240 nm, and 3) can evaporate away from the sample.