Patent ID: 7794932

Claim:
A method for isolating purified RNA from a biological sample comprising a) treating the biological sample with a reagent comprising phenol that when added to the biological sample at a final phenol concentration is from about 10% w/w to about 60% w/w and at least one ribonuclease inhibitor, b) mixing the mixture containing biological sample from step (a) with at least one hydrophobic solvent and a buffer at a concentration sufficient to maintain a pH in the range from about pH 3.6 to below pH 4.0, c) separating an aqueous phase from the mixture obtained in step (b) by sedimentation and recovering purified RNA from an aqueous phase by precipitation with about an equal volume of a water-soluble organic solvent which is RNA that does not reveal the presence of DNA when assayed by reverse transcription polymerase chain reaction (RT-PCR), and d) washing and solubilizing the precipitated RNA.