A COMPARATIVE-STUDY ON THE EFFECT OF HYDROCHLORIC, PHOSPHORIC, AND TRIFLUOROACETIC-ACID IN THE REVERSED-PHASE CHROMATOGRAPHY OF ANGIOTENSINS AND RELATED PEPTIDES

This paper examines the effect of hydrochloric acid as an alternative mobile phase additive in reversed phase chromatography of closely related peptides, such as the analogs of human angiotensin I and III, in comparison to the retention behavior and selectivity obtained with the two most popular additives TFA and phosphoric acid. The effect of the concentration of the additive and of the apparent pH of the mobile phase was investigated by isocratic elution of the selected peptides on a totally porous butyl-silica column with water-acetonitrile eluents containing either additive at various concentrations, corresponding to different values of the apparent pH of the mobile phase within the range 1.23 to 2.28. Differences in retention behavior and selectivity observed with the three mobile phase additives were discussed in terms of differences in the ion-pair associations between the ionized peptides and the counterions in the mobile phase.