Chromatofocusing of peptides on a sulfo-cation-exchange sorbent

Simple mobile phases containing no more than two active components were proposed for the formation of ascending pH gradients in a column filled with a sulfo-cation-exchange sorbent. The smoothest nearly linear pH gradients were obtained with the use of citric acid and Tris or NaH₂PO₄ and Tris as active components of the eluent and adjusting ionic strength (up to 0.1–0.3) in the starting solution or eluent; however, in the case of UV detection, the use of NaH₂PO₄ is preferable because of lower light absorption. Potentialities of the proposed approach in the chromatography of peptide mixtures on a sulfo-cation-exchange sorbent were demonstrated. Additions of acetonitrile to mobile phases improve the selectivity of the separation of peptides.