(EN) A method for purifying plasmid DNA through precipitation with a condensating agent and column chromatography is provided. A short chain polymeric alcohol, preferably polyethylene glycol, or another DNA condensation agent, is added to a DNA sample prior to column chromatography. The short chain polymeric alcohol or condensation agent promotes improved isolation of plasmid DNA and may be used for large scale purification, particularly for manufacturing plasmid DNA as a biopharmaceutical.