An automated workstation for preparing ultra-filtrate in one or more disposable ultra-filtration apparatus, the automated workstation comprising: a controller; one or more cartridge racks for holding one or more disposable ultra-filtration cartridges (20, 40, 50, 142) of the one or more disposable ultra-filtration apparatus; one or more sample tube racks for holding one or more sample tubes; one or more pipetting tip racks for holding one or more disposable pipetting tips (70, 122) of the one or more disposable ultra-filtration apparatus, each disposable pipetting tip (70, 122) comprising a positive displacement pipetting tip having a piston; a base, the base comprising cartridge rack positions for positioning the one or more cartridge racks in predetermined locations, sample tube rack positions for positioning the one or more sample tube racks in predetermined locations, and pipetting tip rack positions for positioning the one or more pipetting tip racks in predetermined locations; cartridge rack detectors for detecting the presence of a cartridge rack of the one or more cartridge racks on the base at the predetermined locations, the cartridge rack detectors having an output element for signaling the presence of the cartridge rack to the controller; sample tube rack detectors for detecting the presence of a sample tube rack of the one or more sample tube racks on the base at the predetermined locations, the sample tube rack detectors having an output element for signaling the presence of the sample tube rack to the controller; pipetting tip rack detectors for detecting the presence of a pipetting tip rack of the one or more pipetting tip racks on the base at the predetermined locations, the pipetting tip rack detectors having an output element for signaling the presence of the pipetting tip rack to the controller; a pipetting tool comprising resilient fingers that open radially by movement against a force exerted by a spring for grabbing a pipetting tip piston gripping stem of the one or more disposable pipetting tips (70, 122); a movable arm, supported from the base, the movable arm supporting the pipetting tool; and a waste container for receiving the one or more disposable pipetting tips (70, 122) released by the pipetting tool. a controller; one or more cartridge racks for holding one or more disposable ultra-filtration cartridges (20, 40, 50, 142) of the one or more disposable ultra-filtration apparatus; one or more sample tube racks for holding one or more sample tubes; one or more pipetting tip racks for holding one or more disposable pipetting tips (70, 122) of the one or more disposable ultra-filtration apparatus, each disposable pipetting tip (70, 122) comprising a positive displacement pipetting tip having a piston; a base, the base comprising cartridge rack positions for positioning the one or more cartridge racks in predetermined locations, sample tube rack positions for positioning the one or more sample tube racks in predetermined locations, and pipetting tip rack positions for positioning the one or more pipetting tip racks in predetermined locations; cartridge rack detectors for detecting the presence of a cartridge rack of the one or more cartridge racks on the base at the predetermined locations, the cartridge rack detectors having an output element for signaling the presence of the cartridge rack to the controller; sample tube rack detectors for detecting the presence of a sample tube rack of the one or more sample tube racks on the base at the predetermined locations, the sample tube rack detectors having an output element for signaling the presence of the sample tube rack to the controller; pipetting tip rack detectors for detecting the presence of a pipetting tip rack of the one or more pipetting tip racks on the base at the predetermined locations, the pipetting tip rack detectors having an output element for signaling the presence of the pipetting tip rack to the controller; a pipetting tool comprising resilient fingers that open radially by movement against a force exerted by a spring for grabbing a pipetting tip piston gripping stem of the one or more disposable pipetting tips (70, 122); a movable arm, supported from the base, the movable arm supporting the pipetting tool; and a waste container for receiving the one or more disposable pipetting tips (70, 122) released by the pipetting tool.