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validation of biomagnetic separation processes, magnetic bead separation

The two critical points necessary to achieve homogeneous Magnetic Bead Separation conditions

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 Magnetic Bead Separation Processes:

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

Typically, Magnetic Beat 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 Magnetic Bead 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 Magnetic Bead 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 Magnetic Bead Separation process homogeneous? Are you controlling the two critical points for homogeneity? New developments in Magnetic Bead Separators provide you with the tools for  homogeneity or similarity.

Homogeneous magnetic fields are important for magnetic bead separation

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:


magnetic bead separation processes validation

Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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