While it might be thought that ‘bigger is better’ during a scale-up process, merely using a larger magnet in a **magnetic separation rack** for larger volumes generates very different conditions. This leads to **inconsistencies and other problems** with the final product.

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**:

## Working with a small magnetic separation rack

In **small working volumes**, acceptable conditions are worked out, but when scaling up, those conditions do not seem to work well. Specifically, when one looks at the **gradient of the magnetic field**, the magnitude of the gradient is **related to the magnetic force** when the beads are saturated.

This gradient will vary greatly with the **size of the magnet and the volume of the sample**. For example, if the beads are in a 5 cm bottle (diameter), and a small magnet (with dimensions = 2 x 1 x 0.5 cm) is used as **magnetic separation rack**, the magnetic force would be between 3 and 5 T/m.

## Increasing magnetic separation rack volume

When working with a **larger volume**, such as a bottle with a diameter of 10 cm (~four times the volume of the above example), there is a temptation to use a **larger magnet as magnetic separation rack**, in order to counter the larger volume. If the magnet has dimension of, for example, 4 x 2 x 1 cm, the magnetic force experienced by the farthest beads from the magnet would be slightly more than 1.5 T/m and would never exceed 2.5 T/m.

This is always **below the minimum value of the smaller volume** example. Even if you increase the magnet size even further (e.g. 8 x 4 x 2 cm), this will not help **because the force will be even weaker**.

Therefore, just **increasing the size of the magnet will not help separate beads** in larger volumes. This is a problem that must not be solved by increasing the magnetic field, but must be **solved by increasing the gradient** of the magnetic field.

Because of this problem, scaling up of non-homogeneous biomagnetic separation systems is never straightforward. Thankfully, modern **homogeneous biomagnetic separation systems** solve this problem because the **magnetic force is well-defined**.

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**:

- Why Do Larger Batches Not Have the Same Characteristics as Smaller Batches?
- Why do Larger Non-Homogeneous Magnetic Separators Have Higher Losses of Magnetic Beads and Biomolecules?
- Why are there More Magnetic Bead Irreversible Aggregation Problems in Non-Homogeneous magnetic separators

Check www.sepmag.eu/ebooks 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!