An apparatus and method for carrying out the affinity separation of a target
substance
from a liquid test medium by mixing magnetic particles having surface immobilized
ligand or receptor within the test medium to promote an affinity binding reaction
between the ligand and the target substance. The test medium with the magnetic
particles in a suitable container is removably mounted in an apparatus that creates
a magnetic field gradient in the test medium. This magnetic gradient is used to
induce the magnetic particles to move, thereby effecting mixing. The mixing is
achieved either by movement of a magnet relative to a stationary container or movement
of the container relative to a stationary magnet. In either case, the magnetic
particles experience a continuous angular position change with the magnet. Concurrently
with the relative angular movement between the magnet and the magnetic particles,
the magnet is also moved along the length of the container causing the magnetic
field gradient to sweep the entire length of the container. After the desired time,
sufficient for the affinity reaction to occur, movement of the magnetic gradient
is ended, whereby the magnetic particles are immobilized on the inside wall of
the container nearest to the magnetic source. The remaining test medium is removed
while the magnetic particles are retained on the wall of the container. The test
medium or the particles may then be subjected to further processing.
