An analytical instrument fitting assembly for coupling first and second analytical fluid conduits is provided. The fitting assembly includes a first fitting defining a central passage adapted to receive a first fluid conduit defining an internal diameter of no greater than 0.040 inch and a second fitting. The second fitting defines a central passage extending between first and second ends and is in fluid communication with the first fitting. A separation device is disposed within a central passages of the first and second fittings to selectively separate liquids passing therethrough. The fitting assembly further includes a retractable end fitting having a housing, a tube extending within the housing, and a biasing member. Selective positioning of the tube within the housing minimizes dead space between the tube and the second end.