Differential Magnetic Catch and Release: Analysis and Separation of Magnetic Nanoparticles

Abstract

This article reports the purification and separation of magnetic nanoparticle mixtures using differential magnetic catch and release (DMCR). This method applies a variable magnetic flux orthogonal to the flow direction in an open tubular capillary to trap and controllably release magnetic nanoparticles. Magnetic moments of 8, 12, and 17 nm diameter CoFe2O4 nanoparticles are calculated using the applied magnetic flux and experimentally determined force required to trap 50% of the particle sample. Balancing the relative strengths of the drag and magnetic forces enables separation and purification of magnetic CoFe2O4 nanoparticle samples with <20 nm diameters. Samples were characterized by transmission electron microscopy to determine the average size and size dispersity of the sample population. DMCR is further demonstrated to be useful for separation of a magnetic nanoparticle mixture, resulting in samples with narrowed size distributions.

Preparation of polypyrrole-coated magnetic particles for micro solid-phase extraction of phthalates in water by gas chromatography–mass spectrometry analysis

“…Also, magnetic particles can be collected and separated from liquid phase simply under a magnetic field, which avoids the tedious filtration or centrifugation procedure [5][6][7], and makes the particles easy to retrieve with low cost. These intriguing features of magnetic separation have led to its numerous applications in many research fields such as bio-separation [8][9][10][11][12]. While, due to the dipole-dipole interactions, the particles are easy to aggregate, which restricts the application of magnetic particles.…”

Isolation of cells for selective treatment and analysis using a magnetic microfluidic chip

“…12 The magnetic elements can be either passive or active; passive elements are usually softferromagnetic structures, [13][14][15][16][17][18] while active elements are microelectromagnets. [19][20][21][22][23][24][25] Soft-ferromagnetic structures can be magnetized by applying an external magnetic field and demagnetized by removing the field. They usually provide stronger magnetic fields than micro-electromagnets and are employed to spatially concentrate magnetic fields.…”

Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores

“…[41][42][43][44] Their versatility has been demonstrated by use in conjunction with techniques such as the polymerase chain reaction, 45 mass spectroscopy, 46 and high-throughput linear magnetophoresis (LM) assays. 41,[47][48][49][50] Precise application of magnetic fields has enabled device-based quadrupole sorting, [51][52][53][54] active bead transport for biosensing, 55 and dynamic manipulation of magnetic supraparticle structures (SPSs). 56 For applications in which target analytes contain multiple binding sites or epitopes, it is possible for the target to bind to multiple beads simultaneously, leading to aggregation.…”