Ultrafiltration is an alternative to ethanol precipitation for the concentration and desalting of nucleic acid solutions.  It requires no phase change and is particularly useful for dealing with very low concentrations of nucleic acids.  This method or protocol describes the use of the Microcon cartridge, a centrifugal ultrafiltration device, to concentrate and desalt nucleic acid solutions.

Protocol: Concentrating and Desalting Nucleic Acids with Microconcentrators Protocol