A method for removing a target
DNA fragment having a predetermined base-pair length from a mixture of
DNA fragments comprises the following steps. A mixture of
DNA fragments which may contain the target DNA fragments is applied to a
separation column containing media having a nonpolar, nonporous surface, the mixture of DNA fragments being in a first
solvent mixture containing a
counterion and
a DNA binding concentration of driving
solvent in a cosolvent. The target DNA fragments are separated from the media by contacting it with a second
solvent solution containing a
counterion and a concentration of driving solvent in cosolvent which has been predetermined to remove DNA fragments having the target DNA fragment
base pair length from the media. The target DNA fragments can be collected and optionally amplified. When the method is being applied to collect a putative fragment, if present, no DNA fragments having the
base pair length of the target DNA could be present in the mixture. Alternatively, DNA fragments having the
base pair length of the target DNA are present in the mixture. The disclosure also describes an ambient or low pressure device for separating
polynucleotide fragments from a mixture of
polynucleotide fragments comprises a tube having an upper solution input chamber, a lower eluant receiving chamber, and a fixed unit of separation media supported therein. The separation media has nonpolar separation surfaces which are free from multivalent cations which would react with
counterion to form an insoluble polar
coating on the surface of the separation media.