Any additives with primary amine groups, such as free amino acids or Tris buffer, are incompatible. This is because the label used after the sizing step is amine reactive, so any primary amine containing species would be labelled alongside the protein or peptide of interest. You would need to perform a buffer exchange step to remove these additives before testing.
For other additives, our internal testing has found that Ethanol (EtOH) up to 5% does not affect the results. DMSO can result in a slight decrease in concentration reported. This can be controlled by calibrating with a known concentration sample that has the same % of DMSO.
Learn more about the effect of ethanol or DMSO in samples here.
If your samples contain other additives, please contact us to ask about their effect on the results.