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Posted on Wed, Mar 13, 2013

Determining the Optimal Biomagnetic Separation Time

Magnetic bead separation with permanent magnets aid lot consistency

Those who use Life Sciences products rightly demand that these products show consistency from batch to batch. In other words, when comparing batches, one should find very little, if any, variability.

In biomagnetic separation devices that use permanent magnets, such as magnetic bead separation devices, the working conditions are generally very stable. The main parameter that needs to be determined in any given assay situation is the separation time, i.e. the time that the beads are exposed to defined biomagnetic separation conditions.

This post is about magnetic bead separation and how to validate this process. If you are interested in this topic, and are willing to learn more about it, download our Free Guide The Starting Guide to Validate Biomagnetic Separation Processes:

Free PDF guide:   "Validation of Magnetic Bead Separation Processes" 

The problem

When one uses standard biomagnetic separation devices, the magnetic conditions under which the beads are separated are non-homogenous. In other words, beads that are far from the magnets experience very weak forces and magnetic fields. In order to prevent or minimize loss of material, typically the separation time needs to be extended for these beads.

Near the final retention position of the beads, the magnetic forces and fields are high. If the beads are exposed to high forces for a long period of time, there is a great risk of bead aggregation and inability to resuspend the beads.

These are two opposing situations that exist in the same vessel. If one decides to separate the beads over a longer period of time, the risk of irreversible aggregation increases. If one shortens the separation time, beads farther from the magnet will be lost.

Magnetic bead separation time differences yield heterogeneous results

How can this be resolved?

Newer Sepmag’s biomagnetic separation technology uses homogenous conditions where the magnetic force is the same, regardless of the distance from the magnets. Since the force does not decrease with distance as in traditional devices, the gentle retention forces will hold the beads during buffer extraction. Since the forces on the beads at a distance are the same as the forces on the beads closer to the magnets, separation time will be much shorter than in non-homogenous systems. All of the beads move at the same speed, so separation times can easily be determined using optical methods.

These optical techniques can also be utilized to make sure the separation is complete. Since the beads will be exposed to the magnetic force for a much shorter time overall, the risk of irreversible aggregation is greatly reduced.

If you found this article interesting and want to get a deeper insight in the topic of magnetic bead separation, make sure to check these articles from our blog:

Dr. Lluís Martínez

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