When purifying crude peptides, we always use a mobile phase modifier. The modifier simplifies a potentially complex purification by driving the desired peptide, and any impurities in the sample, into a single protonation state. That way, you're only trying to purify a single peptide, rather than many variants of the same peptide that only differ by the presence or absence of a couple protons - from many peaks to one!
Acids are commonly used as mobile phase modifiers. Some groups choose trifluoracetic acid (TFA), while others choose formic acid (FA). But are there others that should be considered as well? In today's post, I'll explore the use of an acidic buffer as a mobile phase modifier and compare the purification efficiency to that observed with TFA.