The feasibility of a magnetic separator device for ex-vivo blood detoxification was studied. This blood detoxification approach entails administering functionalized magnetic microspheres (FMMSs) into a patient's body by transdermal injection to capture and remove toxins from the blood using highly specific receptors attached to the surface of the FMMSs. These toxin-loaded FMMSs are then removed from the body using extracorporeal blood circulation through a specially designed magnetic separator, based on high gradient magnetic separation principles. The performance of the magnetic separator, in terms of its collection efficiency (CE) of the FMMSs, was evaluated theoretically using a streamline analysis of a 2-D model. The effects of blood velocity (1 to 20cm/s), magnetic field strength (0.1 to 2.0T), wire size (0.125 to 2.0mm in radii), separator unit size at a fixed ratio of tube to wire diameter of one, tube length (2.0 to 20cm), wire material (nickel, SS 430 and wairauite), and magnetic material comprising the FMMSs (iron, typical magnetite and weaker magnetite) on the CE were evaluated. Provided that the blood velocity was below 2cm/s, CEs > 80% could be attained under reasonable conditions, like when using FMMSs 400nm in diameter and containing 60wt% magnetite in a magnetic field of 0.5T using a magnetic separator with 0.5mm radii wire (at a fixed ratio of tube to wire diameter of close to one) that was 10cm in length (same as the tube) and made of SS 430. CEs of between 30% and 80% could also be attained at blood velocities up to 20cm/s without compromising the magnetic separator design. The magnetic separator performance improved by reducing the size of the unit with tubes and wires of equal radii, increasing the applied magnetic field strength, utilizing magnetic materials with the highest magnetizations, and increasing the length of the unit. Overall, the results from this study delineated the physically realistic conditions that make ex vivo blood detoxification possible with this magnetic separator device.