Method and apparatus for wash, resuspension, recollection and localization of magnetizable particles in assays using magnetic separation technology

A method of separating and selectively washing magnetic particles within a reaction vessel, said magnetic particles having sample components bound thereto, the method comprising the steps of:

• passing said reaction vessel through an array of reaction vessel positions of an assay apparatus, comprising an initial separation stage, a resuspension wash position, a subsequent separation stage, a final aspiration position, and a final resuspension position, for separating said magnetic particles from a liquid phase in said reaction vessel and washing said magnetic particles free of unbound sample components, wherein:
• said initial separation stage comprised of a first consecutive plurality of said reaction vessel positions and an initial aspiration element, adjacent a first of said reaction vessel positions of said initial separation stage, for selectively aspirating a quantity of liquid phase from said reaction vessel at said initial separation stage first reaction vessel position;
• said resuspension wash position comprised of one of said reaction vessel positions, adjacent said initial separation stage, and a resuspension wash dispense element, adjacent said resuspension wash position, for selectively dispensing resuspension wash buffer into said reaction vessel at said resuspension wash position;
• said subsequent separation stage comprised of a second consecutive plurality of said reaction vessel positions, adjacent said resuspension wash position;
• a final aspiration position comprised of one of said reaction vessel positions, adjacent said subsequent separation stage, and a final aspiration element, adjacent said final aspiration position, for selectively aspirating a quantity of liquid phase from said reaction vessel at said final aspiration position;
• and
• a final resuspension position comprised of one of said reaction vessel positions, adjacent said final aspiration position, and a reagent dispense element, adjacent said final resuspension position, for selectively dispensing a reagent into said reaction vessel at said final resuspension position to resuspend said magnetic particles in said reagent,
• wherein said array is configured such that said reaction vessel transits, in sequential order, said initial separation stage, said resuspension wash position, said subsequent separation stage, said final aspiration position, and said final resuspension position, and
• wherein said magnet adjacent said resuspension wash position is of reduced magnetic strength relative to all other magnets adjacent said array of plural consecutive reaction vessel positions.