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Why Do Larger Batches Not Have the Same Characteristics as Smaller Batches?

When a non-homogenous magnetic separation rack (a classical system) is used for scaling up a process, the conditions for a larger batch will completely change from the smaller batch. In these classical non-homogeneous magnetic separator, both the magnetic field gradient and the magnetic state of the beads (either linear or saturated) will vary depending on their position and relative distance to the magnet.

This post is about biomagnetic separation with a magnetic separation rack, and how to scale-up this process. If you are interested in this topic, download our free ebook The Basic Guide to Scale-up Biomagnetic Separation Processes:

Download our Free Guide on Biomagnetic Separation Scale-up HERE.

Magnetic bead behavior in a magnetic separation rack

Beads in a smaller field will have linear characteristics and beads in a higher field will be saturated. The magnetic field gradient also varies, often varying maximally at a particular distance and then becoming less variable again at a greater distance.

Magnetic separation rack saturation vs linear response

Even if the force distribution is good enough to generate optimal characteristics of the product (i.e. small losses with no irreversible aggregation), the use of a different device, either larger or smaller, all the parameters previously determined or observed will completely change for the new magnetic separation rack. The force experienced, for example, by a particular percentage of beads will be different from one device to the other and will depend on their relative position to the magnets.

This happens because the magnetic state of the beads will change due to the differences in the magnetic field intensity. It will be very difficult to reproduce the parameters over the entire new volume with a non-homogenous system. Because of this, the characteristics of the lot will be completely different from the initial lot. There will be greater aggregation and coating problems among other difficulties. And while it is possible that the final product’s functionality will not be changed in any appreciable way, more often than not, variations of the magnetic force due to a different device has a huge impact on the performance of the final product.

Magnetic bead behavior in advanced systems

In homogeneous biomagnetic separation systems, you have more control over the conditions since the parameters are well defined and easy to reproduce at various scales of production. Therefore the problems normally seen in scaling up with non-homogeneous systems do not manifest in homogeneous systems.


Magnetic separation rack response vs linear response 

Don’t forget to check these posts from our blog in order to get a deeper insight into the scaling-up of biomagnetic separation processes:

Check to access to FREE eBooks on the subject, or contact us. We will be glad to help you to achieve an efficient magnetic bead separation process!

magnetic separation rack

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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