Chromatography Forum

We got the system. It keep shutting down due to the low pressure. Pumps the mobile phase fine - no make sound like air in pump head. Low pressure happen after several injeculations of sample. Anyone know of possible air trap in inject path? Best way remove if is present how?

If you run for the same length of time but do not inject samples, does the low pressure shutdown still occur?

Thanks for taking time to reply kind sir. Pump flow fine for long time today. Problem only happen after injeculations. It is quite random. Seem to happen after sample has been injeculated onto column mostly.

Okay, that's a start. Most injection valves have two positions: "load" and "inject". If you can, start the pump with the valve in the "inject" position. If the low pressure situation occurs, that says that you probably have a leak: either where the sample loop connects to the valve or else internally in the valve.

Carefully check all of your fittings for evidence of leakage. If everything is tight, you might consider replacing the injection valve.