(I) Rapid and Selective Electro-Filtration / Concentration
The sample is placed in a compartment comprising the Dialysis Chamber (1) and the union. The MWCO of membrane (b) is larger than the molecular weight of the biological molecule of interest, while the MWCO of membrane (a) is smaller. Upon application of the electric field, the biological molecule of interest will pass through membrane (b) and collect in Dialysis Chamber (2) while smaller molecules will pass through membranes (a) and (b) and Dialysis Chamber (2) as a result. This is a fast and effective method for the concentration of small samples as well as selective filtration.

(II) Gel extraction of DNA and protein by Electroelution
By using the ElectroPrep™ system as shown in the schematic diagram, proteins and DNA can be eluted from a gel slice quickly and easily with excellent recovery. By using a Union, Dialysis Chambers can be joined in any combination necessary to accommodate the size of the gel slice. Samples can be concentrated if desired, by choosing a receiving chamber with a smaller volume. The MWCO of the membranes (a and b) can also be chosen to achieve very selective filtration. Membrane (b) should have a MWCO greater than the molecular weight of the sample of interest, while membranes (a) and (c) are smaller. The same principle applies as described in (I).

(III) Selective Electro-Filtration / Concentration / Separation Based on Different Charges of Biological Molecules
In this configuration of the ElectroPrep™, the sample is placed in a Union between two membranes (b), both of which should have a MWCO larger than the molecular weight of the molecule of interest, while the MWCOs of membranes (a) and (c) are smaller. Each biological molecule, including the molecule of interest, will then move either to Dialysis Chamber (1) or Dialysis Chamber (2), depending on its respective charge polarity (i.e. positive or negative), whereas those biological molecules with molecular weights lower than the sample of interest will migrate through membranes (a) and (c) into the tank. Biological molecules with unknown isoelectric points can also be separated and purified in this manner. Dialysis Chambers of smaller volumes can be used to concentrate dialysed product.

(IV) Electrodialysis through Simultaneous Exchange of Buffers - e.g. cleaning up PCR®products
Following amplification, the PCR® product is placed in the Dialysis Chamber between membranes (a) and (b), each membrane having a MWCO lower than the molecular weight of the PCR? product but not the primer. Upon application of the electric field, dialysis occurs quickly by the simultaneous exchange of buffer, resulting in the migration of the lower molecular weight primers through membranes (a) and (b) while the purified PCR? product is retained in the Dialysis Chamber. Electrodialysis is also effective for desalting neutral molecules that do not move in an electric field (such as sugars) or charged molecules at their isoelectric point.