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When Magnetic Bead Separation is used in production processes, quality control becomes a priority. The first step is to define and validate the process, but then the key point is checking the repeatability of every single batch. 

Free PDF guide: "The Basic Guide  for Monitoring Biomagnetic Separation Processes"

To define and validate the process it is important to know the working conditions. To exert a constant force over the entire batch volume, the magnetic field pattern needs to fulfill two conditions:

  • All magnetic beads must be in the same state (saturated or constant susceptibility)
  • The spatial magnetic field variation should be a constant gradient (if beads are saturated) or a constant gradient of the square of the field (if beads have constant susceptibility).

Having a constant force over the entire batch volume ensures in-batch consistency. If generated by permanent magnets, the magnetic field pattern is the same for every batchIn such conditions, quality problems only appear in the magnetic bead suspension. As the characteristics of the beads and/or the buffer may change from batch to batch, the purpose of monitoring the process is to quickly detect any variations in the suspension through changes in the Magnetic Bead Separation behavior. To do this, we need to define a ‘standard’ curve to serve as reference.

This article explains the advantages of monitoring Magnetic Bead Separation processes. If you are interested in knowing more about this innovation download our free basic guide for monitoring Magnetic Bead Separation processes:

Free PDF guide: "The Basic Guide  for Monitoring Biomagnetic Separation Processes"

One way to define the standard curve for a given process is to collect the data from the first batches and use this data to define the process. The example shown in the figure plots 15 validated batches. The resultant parameters for the separation curve are t50=33.5 (σ=1.7) and p=3.25 (σ=0.08).

The acceptable tolerance for the parameters is still controversial. Some users consider that the obtained separation curves are more sensitive to variations than the final application of the beads (usually CLIA). This means that over-tightening the acceptance criteria may lead to batches being discarded that may be within the tolerances of the diagnostic test.

The issue is still open, but most industrial users of the monitoring technology prefer not to disclose details of this subject, considering the results are sensitive, proprietary information.

In any case, the parameterization of the curves makes it possible to build standards that enable production and quality assurance teams to discuss the acceptance criteria with quantitative data. A far less controversial method than the OK/ NO OK alternative used when Magnetic Bead Separation depended on suspension transparency evaluated visually at the fixed separation time.

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FREE Download: Basic guide to magnetic bead cell separation

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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