1. Stop the Buffer and Reagent Pumps.

2. Remove the cap from the associated Buffer or Reagent (Ninhydrin) bottle to release the Nitrogen pressure. If you are replacing the Valves on the Ninhydrin pump place the bottle on the bench next to the analyzer to reduce the flow. If you have a connector available block off the Ninhydrin inlet tubing.

CAUTION: Remove and replace the check-valves one by one to avoid a possible mix-up with the inlet and outlet valves.

3. Remove the tubing from the check-valve to be replaced.
   
4. Place the new check valve cartridge into a beaker of Isopropanol for 2 – 3 minutes.
5. Remove one check valve at a time to avoid any mix up when installing the new cartridge. Take note of the cartridge orientation
   
6. Once the installation is complete, replace the fitting back into the pump head and reconnect the tubing, replace the associated bottle cap.
7. Follow the normal priming procedure.