An analytical cartridge and a rotary analytical device with which the cartridge cooperates. The cartridge may have a housing, an axis, analysis chambers spaced from and located circumferentially about the axis, and a magnetically movable element located in and movable within each analysis chamber to mix fluid in the analysis chamber. The rotary analytical device may have a housing with a cavity having an axis, an impeller extending into the cavity and rotatable about the axis to receive and rotate the cartridge, a motor to rotate the impeller, at least one magnetic element near the cavity and offset from the axis, a light source in the housing to direct a beam of light into the cavity and through the analysis chamber of the cartridge, and a light sensor to receive light from the analysis chamber.