A mixture of two polymers, or one polymer and a salt, in an aqueous
medium separates into two phases: this phenomenon is useful in biotechn-
ogy for product separations. Separation of biological molecules and
particles in these aqueous two-phase systems (ATPS) was initiated over
40 years ago by P.-Å. Albertsson, and later proved to be of immense
utility in biochemical and cell biological research. A boost in the
application of ATPS was seen when problems of separations in
biotechnology processes were encountered. Its simplicity,
biocompatibility, and amenability to easy scaleup operations make the
use of ATPS very attractive for large-scale bioseparations. Despite the
advantages ATPS enjoys over other separation techniques, the application
of two-phase systems has for a long time been confined to selected
labora- ries. Recent years have, however, shown a trend in which
increasing numbers of researchers employ two-phase partitioning
techniques in both basic and applied research.