Why are there More Problems in Non-Homogeneous Magnetic Separators?
Longer separation times combined with exposure to very high magnetic forces during that time results in an increase in the formation of irreversibly aggregated bead clumps. This problem decreases yield and forces the use of extraordinary resuspension methods such as sonication. Sonication in order to resuspend these clumps adds steps to the separation process which results in a longer time to produce the lot, larger investment of time and money into the process, a longer time to develop the process and more resources necessary in order to validate the process.
You can try to avoid these problems by using a force that is low enough such that you will not be exposing beads to such a high magnetic force over time, but this cannot be done with non-homogeneous separation systems without greatly increasing magnetic bead losses or without using exponentially longer separation times. Using homogeneous separation systems, however, you can both decrease the force and decrease the separation time. The separation time in these systems will be proportional to the diameter of the vessel. Due to the mild force and short separation times irreversible aggregation problems are avoided when using homogenous biomagnetic separation systems.