Apparatus for automatically processing magnetic solid phase reagents

An automatic apparatus for use in assays for separating magnetic particles from a liquid phase, the apparatus comprising:

• a plurality of reaction vessels for holding magnetic particles dispersed in a liquid phase,
• a reaction vessel mounting wheel for moving the plurality of reaction vessels in sequence past at least one processing position,
• probe means for dispensing liquid into and withdrawing liquid from the plurality of reaction vessels,
• a reaction monitoring arm mounted for relative movement with respect to the reaction vessel mounting wheel and to be positioned with its periphery adjacent any of the plurality of reaction vessels,
• a detector positioned on the reaction monitoring arm radially outside of the plurality reaction vessels, the reaction monitoring arm being operable to direct a beam of interrogating radiation through each plurality of reaction vessles to the detector, and
• coupling means coupled to the reaction monitoring arm for selectively positioning a first magnet adjacent the location of the beam of interrogating radiation, but spaced therefrom by the distance separating adjacent plurality of reaction vessels on the reaction vessel mounting wheel.