Abstract: Broad volumetric range pipettes with multi-tiered pipette tip holder and ejection assemblies and methods of using such pipettes are disclosed herein. These pipettes typically include a concentric cylinder arrangement with each outer cylinder configured for contacting and dislodging a pipette tip attached to the tip holder portion of the immediately adjacent inner cylinder. In this manner, different sized pipette tips can be used on a single device. In addition, a locking mechanism is described for locking the large tip holder into a downward position to minimize the extension of the small tip holder and thereby enabling attachment of large, filtered pipette tips and reducing/eliminating the risk that the liquid being transferred will contaminate the pipetting device.

Abstract: A hollow elongated spray arm for transmitting washing liquid from a conduit leading from the pump, the arm having one or more radially extending projections having a plurality of spray orifices therein. The projections include a guide disposed adjacent at least one of the orifices for orienting relatively long slender foreign objects suspended in the washing liquid to insure that such objects can pass through the orifice for later automatic or manual removal from the machine. The orifice is preferably located at the terminus of at least one of the radial projections such that it intersects the end portion thereof.