On a CN column, running with 60:40 Water:MeOH with 0.05% TFA, samples prepared on 50 mM phosphate buffer (pH=6.8), containing SDS were injected. Apart from the fact that retention times are dependant on the concentration of SDS present (presumably because the peaks belong to cations), a downward step is observed in the baseline. It’s been observed that the higher the concentration of SDS is, the earlier this step occurs.