Abstract Air bubbles, seal wear, and salt crystals all cause problems for HPLC pumps. Air in the pump chamber causes fluctuations in the solvent flow. Particles in the check valves can lead to such bubbles. The reciprocating motion of the pump can wear out seals, leading to leaks. Buffers can lead to salt crystal formation, which can damage the pump or affect its performance. Buffers accelerate seal wear.
KeywordsSeals, Buffers, Salt crystals, Wear, Pressure fluctuations, Malfunctions, Check valve, Air bubbles, Particles
LevelBasic
Air-caused malfunction
Malfunctions are usually caused by air present in the check valves or in the pump head. Air in the check valves can indicate the presence of particles in the pump. Air bubbles can also lodge themselves in the pump head. Air manifests itself as a strongly fluctuating flow, and thus, large pressure fluctuations. Bubbles can be removed by purging the pump at 5 ml/minPump head
When the check valves are contaminated, they can be flushed with acetone or 2-propanol and treated in an ultrasonic bath.
Placing the solvent reservoirs at least 30 cm above the pump improves the transfer of mobile phase into the pump heads and minimizes the formation of bubbles.
Wear
The high pressure seals inevitably wear out due to the movement of the piston. The eluent determines the friction between seals and pistons, which in turn determines seal lifetime. If the seals are worn out, leakage may be noticeable at the back of the pump head. Wear will be more substantial when the eluent contains a buffer.
Salt crystal formation
Damaging salt crystals are always a danger when buffered mobile phases are used. Many pumps allow for the back of the piston to be flushed as it protrudes from the housing in order to remove buffer salt residues. Always flush the pump with water when the pump is out of operation. In general, the pump should be kept running overnight at low flow rate to prevent salt crystal formation.
