Reversed-phase liquid chromatographic separation of platinum(II) complexes of methionine- and histidine-containing peptides using perfluorinated carboxylic acids as ion-pairing reagents

Reversed-phase liquid chromatography with the perfluorinated carboxylic acids trifluoroacetic acid, pentafluoropropanoic acid (PFP) and heptafluorobutyric acid as ion-pairing reagents provides a flexible system for both the analytical and semi-preparative separation of the products of the reaction between [Pt(en)(H2O)(2)](2+) and methionine- and histidine-containing peptides. High selectivity can be achieved by variation of the chain length and concentration of the ion-pairing reagent for organic modifiers (methanol, acetonitrile, tetrahydrofuran) at concentrations in the range 0-20% (v/v). In general, employment of PFP (9.5 mmol l(-1)) and acetonitrile (2-6%, v/v) leads to the best results. The retention behaviour of the peptide complexes is influenced by their charge, hydrophobicity and coordination mode.