The main three subsystems of the ITER Tritium Fuel Processing Plant, the Tokamak Exhaust Processing (TEP) System, the Isotope Separation System (ISS) and the Storage and Delivery System (SDS), are equipped with enough instrumentation to control the various processes. In addition to this system-dedicated instrumentation, a central facility called Analytical System (ANS) has been designed for i) verification and determination of the composition of the various gas mixtures processed in the Tritium Fuel Processing Plant and ii) checking and monitoring the local equipment. The analytical requirements of the subsystems of the ITER tritium plant are summarised. A comparison of various analytical techniques revealed that gas chromatography is the most suitable method. The design of the Analytical System comprising three micro and two conventional gas chromatographs and its safe operation are discussed in detail.