The Agilent 12- and 20-position extraction manifold features a variety of characteristics, including 12 or 20 positions for luer tip SPE cartridges, a simple tip design for easy use of stopcocks or disposable needle tips, a vacuum gauge with control and release valves for monitoring and adjustment of vacuum level, a choice of four racks to accommodate a variety of collection vessels, a three-point interlocking system to ensure proper orientation of racks and keying cartridge position to corresponding collection vessel, chemically resistant and non-contaminating construction of glass, polyethylene, polypropylene, and Delrin components, and individually controlled needle-tipped valves (stopcocks) for flow control of each position.