An analysis system for analysing the constituents of a sample of material is provided. A reference supply conduit supplies a source of a first gas. A carrier supply conduit supplies a source of the first or a second gas. First and second reactors are included. A first auto-sampler provides one or more samples of material, the first auto-sampler having an inlet for receiving gas and an outlet for providing the received gas and a sample to the first reactor. A second auto-sampler provides one or more samples of material, the second auto-sampler having an inlet for receiving gas and an outlet for providing the received gas and a sample to the second reactor. A thermal conductivity detector has first and second channels for identifying the relative conductivity of the gases in each channel. A valve system controls the flow of gas from the supply conduits to the auto-samplers.