An apparatus for and method of enabling enhanced, selective agitation of liquid containing a solid-phase reagent. The apparatus includes at least one liquid-bearing container, a circular tray, and a motor. The liquid-bearing container(s) includes at least one internal baffle that imparts turbulent agitation to the liquid when flowing from one end of the container to an opposite end. The circular tray is adapted for selective rotation about a vertical axis of rotation. The rotary circular tray assembly includes container-receiving stations that selectively retain a respective liquid-bearing container in an inclined or pitched orientation with respect to a horizontal plane. The motor creates centrifugal force, which causes liquid in the container(s) to travel from the first end of the container to the second end of the container via the internal baffle(s), agitating the liquid and the solid-phase portions of the reagent. When gravitational force exceeds the centrifugal force, liquid in the container(s) travels from the second end of the container to the first end of the container via the internal baffle(s), again agitating the liquid and the solid-phase portions of the reagent.