Abstract: A gas chromatography assembly has a substrate wafer with grooves and a valve seat etched therein. A plate cooperates with the wafer and the grooves to define gas channels: a carrier gas channel and a sample gas channel, each passing through the valve seat. A valve actuator is attached to the valve seat for controlling the flow of sample gas from the sample gas channel into the carrier gas channel. A pump is attached to the wafer and is connected to the sample gas channel. The pump cooperates with the valve actuator to inject sample gas from the sample gas channel into the carrier gas channel. A modular capillary tube and a detector are connected to the carrier gas channel to analyze the properties of the sample gas flowing in the carrier gas channel from the sample gas channel.