Desalting Oligonucleotides by Butanol Extraction

1. 1. Dry the oligonucleotide on the speed-vac prior to butanol extraction.
      
      
   2. Re-suspend the oligonucleotide in 100 m l of water (HPLC grade or better) and transfer to a microfuge tube. Votex until the oligonucleotide is completely in solution.
      
      
   3. Add 1 ml of butanol to the tube and vortex for fifteen seconds.
      
      
   4. Spin the oligonucleotide in a microfuge for 4 minutes at 11K RPM.
      
      
   5. Inspect the tube and be sure there are two distinct liquid layers present. Re-microfuge the tube if you do not see two distinct layers.
      
      
   6. Immediately pipette the upper liquid layer from the tube and discard. Be careful not to disturb the lower liquid layer at the bottom of the tube. If you wait too long to pipette the upper layer, the layers may begin to mix resulting in lower recovery.
      
      
   7. Again, add 1 ml of Butanol to the tube and vortex for fifteen seconds.
      
      
   8. Microfuge the tube for 4 minutes at 11K RPM.
   9. A pellet should now be visible at the bottom of the tube. Re-microfuge the tube if you can not see a pellet.
      
      
   10. Immediately pipette the supernatant off the pellet and discard. Be careful not to disturb the pellet.
       
       
   11. Dry the pellet on a speed-vac to remove any residual butanol.