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.

An automated pipetting system includes a pipettor. The pipettor includes a pipetting channel, a first plunger mechanism operable to change a pressure in the pipetting channel to aspirate or dispense a liquid, and a second plunger mechanism operable to change the pressure in the pipetting channel to aspirate or dispense the liquid.