DNA purification is a crucial element in a variety of molecular tests, such as PCR and qPCR. It removes contaminants, such as salts, proteins and other impurities that could interfere with downstream processes. It also ensures that the desired DNA is in good condition and pure so that it can be further analysed. The quality of DNA is measured by spectrophotometry (the ratio of A260 to A280) or gel electrophoresis and a variety of other methods.

The initial step in the process of purifying DNA is cell lysis. This is when the cellular structure is broken by reagents or detergents like SDS to release DNA. To further cleanse DNA, reagents which denature proteins, such as sodium dodecylsulfate or Ethylene Diamine Tetraacetic Acid (EDTA) can be added to denature them. The proteins are then removed from the blog nucleic acids solution by centrifugation and washing. If RNA is found in the sample and is not removed, it can be denatured by adding ribonuclease. The nucleic acids are concentrated in ice-cold alcohol to isolate them from other contaminants.

Ethanol can serve as solvents to remove salts or other contaminants from nucleic acids. Researchers can compare results between studies using an average ethanol concentration which is a good choice for high-throughput workflows. Other solvents, like chloroform or phenol can be used, but they are more toxic and require additional steps to avoid cross-contamination. The purification of DNA can be made simpler by using ethanol that has a low ionic strength. This has been demonstrated to work as well as traditional organic solvents at purifying DNA. This is particularly true when combined with spin column-based extract kits.