Nucleic acid purity

Nucleic acid purity can be determined by measuring the absorbance at different wavelengths.

Nucleic acids strongly absorb light at 260 nm, proteins strongly absorb at 280 nm, while chemical contaminants (such as the organic compounds phenol and trizol) absorb light at 230 nm. In addition, absorbance at 320 nm can also be measured to check for any other particulate contamination.
Therefore, you can easily assess nucleic acid purity by calculating the ratio for 260/280 nm, 260/230 nm, and 260/320 nm.

Each ratio has a specific value that determines sample purity:
- For 260/280, a ratio of approximately 1.8 is commonly accepted as pure DNA. For RNA, the ratio should be higher, at around 2.
- For 260/230, a ratio greater than 1.8 is accepted as a pure nucleic acid sample.
- For 260/320, a ratio of 1.8-2.2 generally means that the nucleic acid sample is accepted as pure.