This procedure allows the concentration of DNA samples from dilute solution and the removal of unwanted salts from DNA samples.

Materials

3M Sodium Acetate buffer, pH 5.2 (store at 4 ℃).

Cold 100% Ethanol (-20℃).

Cold 70% Ethanol in sterile dH2O (-20℃).

DNA sample

4 ℃ Microcentrifuge (normal microcentrifuge in cold room works fine). All centrifugations should be on "soft" (no brake) setting.

Procedure

1.Transfer DNA to a container where it fills one fourth the total volume (a 500 µL tube should have no more than 125 µL of DNA solution, for example) .

2.Add one tenth volum of Sodium Acetate buffer to equalize ion concentrations.

3.Add at least two volumes of cold 100% ethanol; let stand in -20℃ freezer for at least one hour.

4.Centrifuge sample for 15 minutes at highest speed in a 4℃ microcentrifuge.

5.Remove as much supernatant as possible with a 1 mL micropipet; recentrifuge, then remove the rest with a 200 µL pipet.

6.Add 200 µL of cold 70% ethanol; centrifuge for 5 minutes in a 4 ℃ centrifuge.

7.Remove supernatant with a 200 µL pipet; evaporate remaining ethanol in a 37 ℃ water bath.

8.Resuspend pellet in desired volume of water or TE buffer.