A check valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.
Utilizing a check valve with a syringe, you can run a continuous cycle experiment at Chemyx Fusion 4000 syringe pump. See the picture below for the Fusion 4000 Independent Channel Syringe Pump set up. The valve is disposable and you can choose different lure fittings for different tubing sizes. The picture below shows two syringes with two check valves and lure fittings and 1/16 tubing on a Fusion 4000 pump.