Basically, MS technique can be classified into two distinct classes, namely HGMS and LGMS, according to the magnitude of magnetic field gradient employed in the separation process.
In fact, HGMS has widely been implemented in the isolation of magnetically responsive particles from their suspension.
To date, HGMS has been proved to be feasible in mineral processing, waste removal, biotechnology, as well as drug delivery. In general, the operation of HGMS involves a column which is filled with randomly entangled magnetically susceptible wires and surrounded by an electromagnet (figure 3a).
By turning on the electromagnet around/besides the column, the magnetically susceptible wires tend to dehomogenize the magnetic field such that high magnetic field gradient (more than 100 T m?1) is produced in the vicinity of the magnetizable wires.
As the suspension of magnetic particles is channelled through the column, the magnetic particles are captured on the magnetically susceptible wires and hence being isolated from the initial solution.
In contrast, LGMS involves only a simple set-up in which the separation of magnetic materials from the solution is performed typically by a hand held permanent magnet without any kind of packing.
Under a non-homogeneous magnetic field produced by the permanent magnet, magnetic particles are driven to migrate towards the magnetic source by magnetophoretic force and therefore being isolated out of the solution (figure 3b). Because the magnitude of magnetic field gradient involved in this set-up is generally less than 100 T m?1, this type of MS technique is denoted as LGMS.