Application of mixed partition–adsorption systems in high-performance liquid chromatography of purines and pyrimidines

Separation of the test mixtures of some purine and pyrimidine derivatives on silicas (types A and B) in adsorption normal-phase (A-NP) and mixed partition–adsorption normal-phase (MPA-NP) mode has been studied. When the A-NP mode is used the peak shapes are unsatisfactory (especially on type A silica). At the same time MPA-NP systems show a good peak symmetry on all silica types. The findings have demonstrated that the MPA-NP mode offers a specific selectivity. This allows MPA-NP systems to supersede reversed-phase systems in some application areas.