Phenol-chloroform extraction followed by ethanol precipitation is a well-established method of purification. It involves mixing an aqueous nucleic acid sample with a phenol-chloroform mixture. The organic phase then separates from the aqueous phase, taking with it any proteins that were in the original sample. Nucleic acids will remain in the aqueous layer of the mixture, along with other contaminants (e.g., salts and carbohydrates). Following centrifugation, the aqueous phase can easily be removed by pipetting. The nucleic acids in the aqueous phase can then be separated from other contaminants by ethanol precipitation. This method works well but is time consuming and requires the use of hazardous solutions.