Samples are lysed and passed through the membrane using centrifugal or vacuum force. The wash and elution solutions are subsequently passed through the membrane, and the sample is collected into a tube by centrifugation or vacuum. Solid phase extraction, such as using a spin-column based extraction method, takes advantage of the fact that DNA binds to silica. The sample containing DNA is added to a column containing a silica gel or silica beads and chaotropic salts. The chaotropic salts disrupt the hydrogen bonding between strands and facilitate the DNA to silica by causing the nucleic acids to become hydrophobic. This exposes the phosphate residues, so they are available for adsorption. The DNA binds to the silica, while the rest of the solution is washed out using ethanol to remove chaotropic salts and other unnecessary constituents. The DNA can then be rehydrated with aqueous low salt solutions, allowing for elution of the DNA from the beads.