DNA purification is a vital process in many molecular tests such as PCR and QPCR. It eliminates contaminants like proteins, salts, and other impurities which could interfere with downstream processes. It also ensures the desired DNA is pure and is present so that it can then be used for further analyses. The quality of DNA is determined by spectrophotometry (the ratio of A260 to A280), gel electrophoresis, and many other methods.

The initial step in the process of purifying DNA is cell lysis, where the cellular structure is disturbed with detergents or reagents like SDS to release DNA. To further purify DNA, reagents designed to denature proteins, such as sodium dodecyl sulfate or Ethylene Diamine Tetraacetic Acid (EDTA) can be added to denature them. The proteins are then removed from the nucleic acids solution by centrifugation and washing. If RNA is detected in the sample then it can be further denatured by adding ribonuclease. Finally, the nucleic acid is diluted using ice-cold alcohol to isolate it from other contaminants.

Ethanol is a common solvent that can be used to eliminate salts and other contaminants from nucleic acid samples. Researchers can compare results between experiments by using an average ethanol concentration which is a good choice for high-throughput workflows. Other solvents, such as chloroform or phenol, could be used, however, they are more harmful and require additional steps to prevent cross-contamination. The process of purifying DNA can be made simpler by using ethanol that has a low ionic strength. This has been demonstrated to be as effective as conventional organic solvents at purifying DNA. This is particularly applicable when paired with a spin column-based DNA extraction kit.

https://mpsciences.com/2021/04/23/dna-purification-processes-for-different-applications/