The invention provides pipette tip columns and automated methods for the purification of nucleic acids including plasmids. Nucleic acids can be purified from unclarified, clarified or partially-clarified cell lysates that contain cell debris. The columns typically include a bed of medium positioned in the pipette tip column, above a bottom frit and with an optional top frit. Plasmid preparation scales include miniprep, midiprep, maxiprep, megaprep and gigaprep.