A manifold assembly has a manifold and can be located between a block and a plate, and serve as a stator for a valve or other component. The manifold, block or plate can have a plurality of ports either integral thereto or removably connected thereto, with the ports adapted to receive and sealingly engage with a tube having an inner tube layer, an outer tube layer, a sleeve, a tip portion, and a nut. Each of the nut, sleeve, inner and outer tubing layers, and tip portion have a passageway therethrough, with at least the passageways in the sleeve, tip portion, outer tube layer, and nut adapted to allow the inner tube layer to pass therethrough or extend over the inner layer. The ends of the tip portion and inner layer together can define a substantially flat surface which can form a seal in a flat-bottomed port of the manifold, block, or plate, which can be used in a component in an analytical instrument system, including for example a liquid chromatography system. The nut, tube, ferrule, and transfer tube or liner tube may comprise biocompatible materials. In addition, the nut may have a slot, such as a slot adapted to allow the tube and the nut to be easily and quickly separated or to allow a portion of the tube to be easily and quickly inserted in the nut.