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When designing a Magnetic Separation Strategy, it is easy to get caught up in the properties of the superparamagnetic beads and how to coat them with the biomolecule of interest (antibodies, antigens, DNA, RNA, oligonucleotides, aptamers…). It is exciting to choose a bead and tailor its surface ligands to perfectly match your target molecule, but don’t stop there! The magnetic separation rack is equally important to a successful identification, isolation, or enrichment protocol. After all, a perfectly designed bead will be useless without a properly designed magnetic rack to efficiently recover it from the solution.

Free PDF guide: "Magnetic Separation Racks for Cell Sorting"


A properly designed magnetic separation rack is essential

A properly designed rack should have well-defined working conditions to ensure that all bead-target conjugates are recovered. The key parameter to standardize the magnetic separation is the magnetic force (link)s with a well-defined magnetic force, the value can be replicated at different magnetic rack geometries, assuring a proper separation regardless of the volume of the sample.

Classic separation racks are not always designed having standardization of the process in mind, but sometimes just try to optimize the separation time in a specific volume.  This can lead to problems with bead recovery, target viability, and when you increase the volume, slow separation times. Advanced separation racks, however, are engineered with standardized magnetic separation conditions (especially constant magnetic force) to obtain high recoverability rates and fast separation times regardless of the specific tube/bottle used, making the magnetic separation process more reproducible, easier, and more effective.

  • Classic magnetic separation racks generate a magnetic force that changes with distance from the retention area. The problem with this design is that a high retention force is needed to collect the beads farthest from the retention area at the expense of the beads closest to the retention area. Excessive force generates irreversible aggregates closest to the retention area, especially if the separation time is largely due to the slow separation speed of the beads farthest away. This lack of consistency may be confusing, and troubleshooters may erroneously look for problems with the beads or coating process. Much time and money can be wasted this way when the problem is a result of the inhomogeneity of the magnetic force from a poorly designed separation device. The magnetic force must be uniform at any distance away from the retention area so that it can affect the farthest beads and avoid losses or very large separation times.This is especially important during Magnetic Bead cell separation. The excessive force generated by a classical separation rack at the retention position can damage cells by causing them to burst or break their cell membranes.


  • Advanced magnetic separation racks. A separation rack that generates a uniform retention force throughout the working volume will not have excessive force at the retention area and is gentle on cells. These types of separation racks will not cause cells to break or burst and will improve cell viability and separation efficiency. This feature will provide many benefits to downstream applications in cell culture and cell-based assays. If the cells are not stressed during the separation process, then they will be healthier throughout the culturing and subsequent assays and have fewer confounding variables. Cells are very susceptible to stress and will release stress molecules that change their morphology and behavior.If a magnetic separation rack introduces too much stress due to excessive force at the retention area, then all downstream cell-based assays may be compromised. The advanced magnetic separation racks generate a magnetic force that is constant over the working volume (i.e. the force is constant regardless of the distance to the retention area). That provides a larger force over the farthest beads, avoiding losses and speeding up the separation process as well as avoiding irreversible aggregation. These features open the door to multiple washings without losing material. Moreover, as all the beads experience the same force at the same time, the consistency is extremely high.


Sepmag manufactures advanced Magnetic Bead Separation racks that offer fast separation time and high recoverability rates. These separation racks ensure that a constant magnetic force is applied during the separation process, and also incorporate real-time monitoring of the process. While the operator can often visualize when separation is complete by watching the solution change from cloudy to clear, software such as the Sepmag MONITOR automatically tracks the progress of the sort, providing quantitative feedback.  Separation time can be properly defined effects of changes in the viscosity of the buffer can be quantified, and identify problems that may affect the separation efficiency.

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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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