1. Add an equal volume of TE (pH7.5-8.0) to phenol, mix well, allow phases to separate.

2. Measure pH of the aqueous phase using a pH paper.

3. Remove and discard upper (aqueous) phase.

4. Repeat steps 1 to 3 until the pH of the aqueous phase is between 7.5-8.0.

5. Cover phenol with a layer of TE (pH7.5-8.0). Store protected from light at 4 degree.