Retention behaviour of peptides, quinolones, diuretics and peptide hormones in liquid chromatography - Influence of ionic strength and pH on chromatographic retention

Peptides, quinolones, diuretics and peptide hormones are important substanc es of biomedical interest. In this work a model describing the effect of pH on retention in liquid chromatography (LC) is established and tested for t hese compounds using an octadecylsilica column. The suggested model uses th e pH value measured in the hydro-organic mixture used as mobile phase inste ad of the pH value in water and takes into account the effect of the activi ty coefficients. The proposed equations permit the prediction of the pH opt imum using a minimum number of measurements and also permit the determinati on of the acidity constants of the compounds considered in the medium used as mobile phase. Moreover, these equations can be combined with the previou sly derived equations, that relate the retention with the solvent compositi on of the mobile phase, to establish a general model that relates the eluti on behaviour of the solute with the significant mobile phase properties: co mposition, pH and ionic strength. (C) 2001 Elsevier Science BN. Ah rights r eserved.