the present invention relates to a device method and kit for the convenient and rapid isolation and purification of nucleic acids , proteins , peptides , carbohydrates and oligosaccharides from heterogeneous biological samples . the device comprises a membrane assembly comprised of layers of microporous , polymeric membranes functionalized with ion - exchange groups . the device is reusable for like samples , relatively inexpensive compared to currently available separation techniques and is disposable , thereby avoiding cross - contamination of biological samples .