Spin column-based nucleic acid purification

This method relies on the fact that nucleic acid will bind to the solid phase of silica under certain conditions.

Depending on the target material, this can include the use of detergent or other buffers, proteinases or other enzymes, heating to various times/temperatures, or mechanical disruption such as cutting with a knife or homogenizer, using a mortar and pestle, or bead-beating with a bead mill.

Generally it takes several washes, often with increasing percentages of ethanol/isopropanol, until the nucleic acid on the silica membrane is free of contaminants.

The last 'wash' is often a dry step to allow the alcohol to evaporate, leaving only purified nucleic acids bound to the column.

Even prior to the nucleic acid methods employed today, it was known that in the presence of chaotropic agents, such as sodium iodide or sodium perchlorate, DNA binds to silica, glass particles or to unicellular algae called diatoms which shield their cell walls with silica.