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During the development of a magnetic bead separation process, scientists put great effort into reproducing the size of the beads, the magnetic charge on the beads, buffer composition, pH and temperature. What is often overlooked, however, is the importance of homogeneous 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:

Typically, biomagnetic separation is performed on biomaterial that will be a part of the In Vitro Diagnostic (IVD) kit. The kits provide investigators with the necessary buffers, beads and specified biomolecules. These kits are produced in large batches. It is important during the production process, that each small aliquot from the batch has exactly the same properties as any other aliquot.

In order for this to occur, all of the beads must experience the same conditions during processing. The generation of homogeneous biomagnetic separation requires that the value of the magnetic force be the same in the entire volume of the batch. The magnetic force is dependent on both the magnetization of the beads and the magnetic field profile.

## How to achieve homogeneous separation conditions

There are two critical points that must be followed in order to achieve homogeneous biomagnetic separation conditions:

### The magnetic field magnitude must be higher than 0.1 Tesla

1. If the magnetic field is low, the magnetization of the beads will change linearly (constant susceptibility).
2. Constant force is obtained by the magnetic field having a variable spatial profile over the batch volume (the gradient of the square of the field modulus constant: B ~ r1/2).
3. Constant magnetic moment of the beads is obtained by making the intensity of the magnetic field high enough that they will be saturated.
4. Magnetite, the most common magnetic material used for magnetic beads, saturates at fields of approximately 0.1 Tesla (~ 80 kA/m).

### Achieving a constant magnetic field gradient

1. If the magnetic beads are saturated, their magnetization will be constant.
2. Under constant magnetization, a constant magnetic force can be achieved by having a magnetic field profile with a constant gradient B ~ r.
3. This constant magnetic force can be achieved in smaller volumes by using a simple four pole permanent magnet arrangement.
4. In larger volumes, the magnet configuration is more sophisticated, but can be built by companies that specialize in this field. Cylindrical arrangements will fulfill this configuration, although 1 – 5% of the volume around the axis will not be perfectly homogenous.

Is your biomagnetic separation process homogeneous? Are you controlling the two critical points for homogeneity? New developments in biomagnetic separators provide you with the tools for biomagnetic homogeneity or similarity.

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