A gas chromatograph comprising two separating devices disposed one behind the other, and through which a material sample is conducted by a carrier gas. A pressure regulator regulates the pressure of the carrier gas introduced into the first separating device. A controllable switching device is arranged between the two separating devices. The switching device contains a main gas path lying between the two separating devices and two auxiliary gas paths, which are connected to the main gas path through connecting gas paths and are both fed with the carrier gas and contain flow resistors and a controllable valve for setting different pressure conditions. The auxiliary gas paths are supplied with the carrier gas through the same pressure regulator to reduce the design and adjustment effort in setting the pressure conditions, where fixed resistors are used for the flow resistors.