Abstract: Methods for separating target particles, from a test medium in which the particles are suspended. The method contemplates utilization of blocking or masking particles which block or mask unwanted biological debris which tends to interfere with formation of complexes by which the target particles can be isolated. After centrifugation, the masking particles create a barrier between unwanted debris and test medium containing the target particles which permits the particles to be manipulated or modified without removing them from the debris. In a preferred aspect, magnetic separation techniques are used. In this aspect, non-magnetic 0.04 micron carboxylated polystyrene blocking particles are employed.

Abstract: Apparatus and methods for separating magnetically responsive particles from a nonmagnetic test medium in which the magnetically responsive particles are suspended. The separator comprises a container comprising, e.g., plurality of multiwell chambers, which hold the nonmagnetic test medium, one or more pins disposed substantially within the test medium, an external magnet for producing a magnetic field within the test medium. The external magnet is proximate the pins so as to create magnetic flux lines, magnetizing the pins and creating a magnetic field substantially parallel to the longitudinal axis of the pins thereof in the test medium. According to the method of the invention, the container holding the test medium is positioned in the separator, producing a magnetic field operative to cause the magnetically responsive particles to be attracted to and adhere to the pins and which is substantially parallel thereto.