Dissolved air is present in water, aqueous buffers, and solvents.
This air will "out gas" during a gradient, leading to bubble formation
which may accumulate in the flow cell. Air bubbles in the flow
cell can be eliminated with a backpressure regulator set at 20
to 60 psi. Air bubbles can also be a problem for check valves.
Trapped Vacuum Pump or Lyophilizer
4-liter Erlenmeyer Filtration Flasks
Rubber Stoppers (sizes 12 and 13)
Rubber Hose to connect flask to trapped vacuum pump
Borosilicate Glass Filter Holder, 47-mm dia. with removable stainless-steel
1. Water (< 2 liters) can be degassed in a rubber-stoppered, 4-liter
Erlenmeyer filtration flask by evacuation with a trapped vacuum
pump. After the bubbling ceases, the water is degassed. Volatile
buffers should be added after degassing. Any solution containing
nonvolatile buffer salts should be filtered through a 0.45-um
nylon filter into the flask and then degassed. Filter buffer concentrate
(1 M solution) and then add to degassed water. Solvents should
be degassed only briefly to avoid collecting solvent in vacuum
2. Alternatively, the buffers can be sparged with helium (He)
gas to displace air gasses.