OPTIMUM CONDITIONS FOR THE SEPARATION OF NUCLEOBASES AND NUCLEOSIDES ON UNMODIFIED SILICA BY HPLC

The retention behavior of nucleobases and nucleosides on unmodified silica with dichloromethane-methanol-water mixtures was systematically investigated. The degree and order of retention can be varied over a wide range by changing the pH, the type and concentration of the acidic additives and by the methanol and water content of the mobile phase. The retention process cannot be considered as simple adsorption but rather as a very complex mixed distribution process of adsorption and absorption including the involvement of ion-pair formation. Further data on the effect of the type of silica (source of supply) on retention behavior, column efficiency and column reproducibility are reported. The practical application of unmodified silica for the separation of nucleobases and nucleosides is demonstrated by the analysis of a hydrolysate of calf thymus DNA.