A pilot rig for a preparative gas chromatograph is described. In order to increase the volume of the samples to be separated different separation columns were investigated. The pilot plant is designed as to operate also with two columns at the same time. To recover the separated H isotopes the pilot rig was equipped with three uranium getters which can be automatically switched to the separation columns by electropneumatic valves. These valves are actuated in response to a detector signal. The maximum sample volume achieved with one separation column is 600 ml (STP) of a three-component mixture (H2, HD and D2) with a purity of 98.5 - 98.7% and even 1000 ml (same mixture) with a 91% purity with respect to the components H2/HD.