Sampling valve basically supports the discrete volumes of the treated samples stream to periodically inject into the carrier gas stream of the chromatograph. Sampling valves are fitted with electric or pneumatic actuators which help them to be operated automatically. Switching valve are critical if binary pumps are used. It allows employment of different desired mobile phases. Switching valve consists of five parts: control unit, connecting device, valve body, a rotor and preloaded assembly.
Select between two columns connected to a single detector requiring auxiliary gas for the second column. The figure shows the 8-port sampling valve with two sample loops used for repetitive sample injections on one column.