Tapered cuvette and method of collecting magnetic particles

A method for collecting and washing magnetic particles in a vessel, comprising:

• a) providing a vessel with magnetic particles, said vessel comprising a planar area particle in a first fluid engagement side;
• b) introducing the vessel into a vessel holder comprising,
• i) a holder lumen,
• ii) a vertical surface comprising a magnet, and
• iii) a lever arm,
• wherein said lever arm is mounted to a pivot point proximal to a lower end of said lever arm;
• reciprocally moving said lever arm from a vertical position to a lever arm tilted position relative to the vertical surface of the holder when said vessel is received in the holder lumen between the vertical surface and said lever arm, biasing said lever arm toward said vertical position;
• c) tilting said vessel with said lever arm to retain the vessel in a tilted position relative to the vertical surface of the holder wherein the particle engagement side of the tilted vessel against the magnet is substantially vertical;
• and
• d) collecting the magnetic particles in said vessel at a bottom portion of said planar area particle engagement side of said vessel by magnetic attraction to said magnet having a flat side creating a uniform magnetic flux density over the flat side, wherein the flat side of the magnet is located adjacent the planar area particle engagement side of the vessel;
• e) moving the magnetic particles attracted to the magnet out of the first fluid along the planar area particle engagement side of said vessel using the magnet;
• f) aspirating the first fluid from said vessel from an aspiration point located and towards a side of the vessel opposing the planar area particle engagement side of the vessel;
• and
• g) injecting a second fluid into said vessel toward the planar area particle engagement side of said vessel.