Peptide purification formulations and methods

A method of purifying peptides from a biological sample, comprising:

• (a) contacting the biological sample with a hydrophobic, polymer-based cation exchange material under acidic conditions, such that the biological sample binds to the cation exchange material, wherein the biological sample comprises:
• (i) at least one peptide,
• (ii) at least one monovalent cationic contaminant and/or a at least one hydrophobic contaminant, and
• (iii) at least one hydrophilic contaminant;
• (b) washing the cation exchange material with a first volatile acidic solution, wherein the first volatile acidic solution comprises 20% or less (v/v) volatile organic solvent, water, and a first volatile acid, such that the at least one peptide is retained on the cation exchange material and the at least one hydrophilic contaminant is removed from the cation exchange material;
• (c) washing the cation exchange material with a first volatile salt solution comprising a second volatile acidic solution, and a first volatile base solution, wherein the second volatile acidic solution comprises greater than 20% (v/v) volatile organic solvent, and water,
• such that the at least one peptide is retained on the cation exchange material and the at least one monovalent cationic and/or the at least one hydrophobic contaminant is removed from the cation exchange material;
• and
• (d) eluting the retained peptide from the cation exchange material with a volatile alkaline or neutral solution, wherein the volatile alkaline or neutral solution comprises a volatile organic solvent, water, and a volatile compound selected from a first or a second volatile base, a first or a second volatile salt, and a combination thereof.