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How do I purify a contaminated DNA sample?

Posted September 2, 2020


There are several ways to purify or clean up a DNA sample.


1.       Organic extraction. Organic extraction involves the addition of organic solvents like phenol and chloroform. It has four steps, a lysis step, a phenol chloroform extraction, an ethanol precipitation, and washing steps. Organic extraction is often used in laboratories because it is cheap, and it yields large quantities of pure DNA.


2.       Silica based membranes. DNA is known to be bound to silica membranes when added with certain salts and at a controlled pH. The contaminants in the cell can be removed by washing and DNA can be removed by using an elution buffer.


3.       Magnetic separation. DNA binds to a magnetic surface like magnetic beads when they are coated with DNA binding antibody or a specific functional group that interacts with the DNA. Once the DNA is bound to magnetic beads, the cell contaminants can be washed, and DNA can be removed by using an elution buffer.


4.       Anion exchange chromatography. In the method of anion exchange, the column is filled with a positively charged substrate which binds the DNA due to its negative charge of phosphates. Contaminants are removed by wash steps, and the purified DNA is eluted using ethanol extraction.

Additional resources

Purification of Genomic DNA with Minimal Contamination of Proteins


Portelite™ Fluorimetric High Sensitivity DNA Quantitation Kit *Optimized for CytoCite™ and Qubit™ Fluorometers*

DNA Concentration Calculator