Development of Quadrupole Magnetic Field-Flow Fractionation: Application to Characterization of Magnetic Colloids and Microparticles

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Development of Quadrupole Magnetic Field-Flow Fractionation: Application to Characterization of Magnetic Colloids and Microparticles.The main objective of the proposed work is to develop magnetic field-flow fractionation (MgFFF) into a powerful tool for characterizing magnetic colloids in terms of their paramagnetic component content. The various FFF techniques are elution-based separation methods in which the degree of retardation of a colloidal material depends on the strength of interaction of the colloid particles with the applied field. The quadrupole magnetic field is radially symmetrical and lends itself to an annular FFF channel geometry. Such a geometry has already been exploited for biological cell sorting using immunospecific magnetic colloid labels. A novel, helical channel geometry is proposed that will have several advantages over a simple annular channel. It has simplified inlet and outlet geometry, it will nullify the effects of varying field strength around the annular circumference, and it will have increased separation length for a given quadrupole magnet. Effort is being devoted to optimizing the channel geometry and operating conditions. The importance of carrier solution chemistry cannot be underestimated because aggregation or chaining of magnetized particles must be avoided. Quadrupole magnetic FFF offers the unique possibility of characterizing colloidal material in terms of its distribution in magnetization. Other techniques yield only a bulk, or mean value for the magnetization. Distribution information would be invaluable to the manufacturers of these materials. The inclusion of a quadrupole electromagnet will broaden the applicability of the instrument. The field strength can be adjusted to suit the magnetic properties of the sample. Using programmed decay of field strength, the instrument will be capable of characterizing magnetically polydisperse particulate samples in which magnetization varies widely from particle to particle. The method will be useful for characterizing microparticles and colloids. It will also lend itself to separation of proteins by functionalizing the surface of the particles to promote selective adsorption.