Apparatus and methods for magnetic separation

A magnetic separator used to separate magnetic particles from a non-magnetic test medium in which said magnetic particles are suspended, the separator comprising:

• a) a non-magnetic container having an opening for receiving said test medium and defining a separation chamber;
• b) one or more magnetic wires, each having a longitudinal axis, positioned within the container and effective in said test medium to intensify a magnetic field gradient generated in the test medium by an applied magnetic field, and a carrier for said wires disposed outside of said separation chamber;
• and
• c) magnetic means having pole pieces confronting each other for generating magnetic flux lines extending between the pole pieces transverse to the longitudinal axis of said wires to generate a magnetic field gradient operative upon the magnetic particles within the test medium to attract said magnetic particles toward the magnetized wires and cause such particles to be adhered to the wires, wherein said non-magnetic container comprises a microtiter well.

A magnetic separator used to separate magnetic particles from a non-magnetic test medium in which said magnetic particles are suspended, the separator comprising:

• a) a non-magnetic container having an opening for receiving said test medium and defining a separation chamber;
• b) one or more magnetic wires, each having a longitudinal axis, positioned within the container and effective in said test medium to intensify a magnetic field gradient generated in the test medium by an applied magnetic field, and a carrier for said wires disposed outside of said separation chamber;
• and
• c) magnetic means having pole pieces confronting each other for generating magnetic flux lines extending between the pole pieces transverse to the longitudinal axis of said wires to generate a magnetic field gradient operative upon the magnetic particles within the test medium to attract said magnetic particles toward the magnetized wires and cause such particles to be adhered to the wires, wherein said non-magnetic container comprises a capillary tube.

A magnetic separator used to separate magnetic particles from a non-magnetic test medium in which said particles are suspended, the separator comprising:

• a) a non-magnetic container with an open top capable of receiving the test medium;
• b) a wire screen both adapted to be held in a fixed position within the container and formed into a triangularly shaped body having a central cavity and open at both ends;
• and
• c) magnetic means for applying a magnetic field substantially transverse to the longitudinal axis of the wires in said wire screen to generate a magnetic field gradient operative upon the magnetic particles within the test medium to attract said magnetic particles toward the magnetized screen and cause such particles to be adhered to the screen.

A method for magnetically separating a target substance from a non-magnetic test medium in a magnetic separator comprising a container with an open top, magnetic wire means positioned within the container providing an exposed surface area and magnetic means for magnetizing the magnetic wire means, the method comprising the steps of:

• a) contacting a quantity of magnetic particles comprising a receptor capable of binding specifically to said target substance within said test medium under conditions causing binding of said receptor to said target substance, resulting in target substance-bearing magnetic particles;
• b) introducing said test medium in which said magnetic particles are suspended into said container holding said magnetic wire means;
• and
• c) positioning said container holding magnetic wire means and said test medium having the suspension of magnetic particles therein adjacent to said magnetic means in order to generate in said test medium a magnetic field gradient operative upon the magnetic particles within the test medium to attract said magnetic particles to the exposed surface area of the magnetized wire and cause such particles to be adhered to said exposed surface, and
• d) controlling the quantity of magnetic particles introduced into the container relative to the exposed surface area of said wire means, and controlling the orientation of said exposed surface area causing said particles to adhere to the surface area in a substantially single layer corresponding in thickness to about the size of said target-substance bearing magnetic particles.

A method for determining a target substance in a test medium suspected of containing said target substance, said method comprising:

• a) contacting said test medium with a quantity of colloidal magnetic particles comprising or adapted to comprise a receptor capable of binding specifically to said target substance, under conditions causing binding of said target substance to said receptor, resulting in target substance-bearing magnetic particles;
• b) introducing said test medium into a separation chamber containing a magnetic field gradient intensifier comprising filamentary material having a magnetic field applied thereto, whereby said magnetic particles are caused to adhere to said filamentary material;
• c) removing said test medium from said separation chamber;
• d) treating said magnetic particles while adhered to said filamentary material for removal of interferring substances;
• and
• e) determining the target substance by analysis of said magnetic particles or said removed test medium.

A method for determining an immunoreactive ligand in a test sample suspected of containing said ligand, said method comprising:

• a) contacting said test sample with a quantity of colloidal magnetic particles comprising or adapted to comprise a first receptor to said ligand, and a second, enzyme-linked receptor to said ligand, under conditions causing binding of said receptors to said ligand, resulting in enzyme and target-substance bearing magnetic particles.
• b) introducing said test medium into a separation chamber including at least one ferromagnetic wire disposed in said chamber with sufficient rigidity to resist substantial deformation when passed into or out of a magnetic field of 4-15 K Gauss and having a magnetic field applied thereto, thereby to produce a magnetic field gradient operative upon said magnetic particles, causing said particles to adhere to said wire;
• c) washing said magnetic particles to remove unbound substances;
• and
• d) determining the activity of said enzyme bound to said particles, as a measure of the presence or quantity of said ligand in said test sample.