Scalable Magnetic Designs to Achieve Comparable Capture Rates and Capture Efficiency across Multiple Vessel Diameters

Abstract

Open gradient magnetic separators utilizing strong permanent magnets are used during a variety of magnetic carrier‐based purification and bead coating processes such as protein separations, nucleic acid isolations, and immunodiagnostics. These purification and bead coating processes are often developed on a small, experimental scale before transfer to a functional process scale for use in industrial and manufacturing settings. Accordingly, the strong magnets used for magnetic carrier separation must be scaled to prevent process variation between batch size due to inadequate wash efficiency and discrepant capture times. Magnetic separator scalability may be defined as the consistent capture of magnetic particles as measured by capture time and capture efficiency (>99%) independent of collection vessel diameter. A mathematical relationship between the average magnetic field magnitude and the cross sectional vessel area has been devised for magnetic separators with magnets arranged in quadrature geometry. Using this correlation, the magnet thickness and material for each magnetic separator may be tailored to create the magnetic field strength and gradient required to achieve comparable capture times across different vessel diameters. Accordingly, four magnetic separators ranging in size from 0.125L to 1L were examined and demonstrated equivalent capture times of >99% microparticle capture at 60 seconds for phosphate buffered saline solutions containing 1% solids using Dynabead M‐270 carboxylic acid microparticles. In addition, a 5L magnetic separator is also discussed. Magnetic scaling relationships and additional experimental outcomes using magnetic microparticles are described herein for the scaled magnetic separators.