Abstract: A method and apparatus for processing and analyzing blood serum includes a capacitive sensing unit for receiving centrifuged test tubes and generating output signals indicative of the boundary position between the separator gel and the blood serum in the tubes, and a computer connected to the sensing unit to receive and analyze the output signals of the capacitive sensing unit. An aspirator/dispenser needle and retainer probe unit is positioned above the sensing unit and is capable of lowering a needle; under the control of the computer, to puncture the stopper of a test tube and then withdraw blood serum. The retainer probe prevents the withdrawal or loosening of the tube stopper upon withdrawal of the needle from the tube. A color sensor inspects the aspirated sample and determines whether it is suitable for analysis.