Abstract

Magnetic chromatography is a promising method for fractionation of magnetic nanoparticles with respect to their size and/or magnetic properties. In this study, we investigate the effect of different magnetic field sources and operation modes on the retention of magnetic nanoparticles which pass through a chromatographic column filled with a fine magnetizable matrix. For nanoparticles in the size range between 50 and 400 nm, both constant magnetic fields and square wave AC fields with amplitudes of around 2 mT, result in retention factors of up to 2, while still showing good particle recoveries of more than 95%. In contrast, when using the ‘on-off’ magnetic field operation reported previously, retention factors of only 1.4 could be achieved. We also demonstrate that single domain magnetic nanoparticles show retention factors of 1.2–1.4 even without the application of an external magnetic field, due to their spontaneous magnetization. By using a combination of online UV-measurement and sample collection followed by the determination of the particle size distribution (PSD) by dynamic light scattering, a quantification of the fractionation efficiency could be achieved. Despite the short column of only 12 cm and the high specific throughput of more than 30 column volumes per hour a separation sharpness of 0.62 could be attained, demonstrating the high potential of the method for scalable nanoparticle fractionation.

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