The aim of this study is to prepare silica based affinity sorbents for the purification of plasmid DNA and ge- nomic DNA. For this purpose, (3-aminopropyl)trimethoxysilane (APTS) is chosen for surface modification of silica particles (average size: 100-150 μm) and silica based affinity sorbent carrying NH2 groups on its surface is obtained. APTS modified and unmodified silica particles are characterized by elemental analysis. Adsorption of genomic DNA on the APTS modified silica particles is performed in continuous and batch systems. Effect of io- nic strength, pH, temperature, initial genomic DNA concentration and flow rate is investigated. In the last part of the study, pEGFP-N3 plasmid DNA is separated from E.coli cells by using the APTS modified silica particles and the results are compared with commercial Qiagen DNA purification kit. The results may be summarized as follows: amount of NH2 groups on the APTS modified silica particles is in the range of 38-60 mmol/g. Maximum adsorption capacity of the APTS modified silica particles is found to be 49.3 mg/g and this value is obtained at pH 7.0. Genomic DNA adsorption capacity of the APTS modified silica particles is increased in continuous system. It is also shown that the APTS modified silica particles can be used after ten adsorption-desorption cycle without any significant decrease in adsorption capacity. The APTS modified silica particles are used for adsorption of plasmid DNA from E.coli cells and adsorption capacity is found to be 0.21 mg/g in continuous system.