Methods and apparatuses for mixing a fluid/media for an assay are disclosed herein. In an embodiment, a mixing device for an immunochemistry system includes a pipette configured to aspirate fluid and/or paramagnetic particles from or dispense fluid and/or paramagnetic particles into a cuvette, at least one nonconcentric mass configured cause the pipette to move in a mixing motion, and a control unit configured to activate the at least one nonconcentric mass while the pipette is located within the cuvette so as to mix the fluid and/or paramagnetic particles within the cuvette.