High-performance liquid chromatography of dicarboxylic porphyrins and metalloporphyrins: retention behaviour and biomedical applications.

The retention behaviour of the main dicarboxylic porphyrins, haemato-, deutero-, meso- and protoporphyrins, together with the Fe, Co, Cu and Zn complexes of meso- and protoporphyrins have been systematically studied. Hydrophobic chromatography with methanol-ammonium acetate buffer systems on reversed-phase columns provided the best selectivity, efficiency and resolution. The retention of the porphyrins is controlled by the relative hydrophobicity of the porphyrin side-chain substituents. The insertion of a metal ion into the porphyrin macrocycle, however, completely alters the electronic environment around the central nitrogen atoms of the porphyrins. The retention is then greatly influenced by the species of inserted metal ion, to accept axial ligands from the mobile phase, although hydrophobic interaction of the side-chain substituents with the stationary phase surface is still an important factor. The retention behaviour can be precisely controlled by adjusting the pH, buffer concentrations and types and proportions of organic solvents in the mobile phase. The analysis of porphyrins and metalloporphyrins in blood, and the determination of ferrochelatase in bone marrow are examples of biomedical applications.