Abstract: There is provided a diaphragm sealed valve particularly advantageous in chromatographic systems. The valve is provided with first and second body and a seal member compressibly positioned therebetween. The first body comprises a first, a second and a common port, each opening and being interconnected to the others in a recessed fluid communication channel extending in a first interface of the first body. The valve is also provided with first and second plungers, each having a closed position wherein the plunger presses down the seal member against the seat of the corresponding port for closing said corresponding port, and an open position wherein the plunger extends away from the seat for allowing a fluid communication between the corresponding port and the channel. Complex valves are also provided as well as chromatographic systems and methods.