Abstract: Cell lysis may be brought about by contacting a suspension of cells with a lysis reagent such as sodium hydroxide solution; subsequent treatment enables organic molecules such as plasmid DNA to be separated from other cell components. Intimate mixing of the cell suspension with lysis reagent is achieved by passage through a fluidic vortex mixer arranged so the residence time of the cell suspension in the mixer is less than the time for lysis to be completed, and may be less than 0.1 seconds. Such a vortex mixer comprises a cylindrical chamber with an axial outlet duct and at least one tangential inlet duct, but with no internal baffles. The low shear stress to which the cell suspension is subjected minimizes loss of product through denaturation or fragmentation of the product, and indeed of contaminants. The subsequent treatment may also utilize a fluidic vortex mixer.