This Information Applies To: Agilent LC Pumps
Modern Chromatography software will allow the users to determine what to do at the end of a sequence run. The entire system can be shut down or only certain modules can be turned off, such as turning off the detector lamp. In the case where the user forgets, there are other ways to at least stop the pump from continuously running when the solvent bottle is empty. A dry pump, which continues to pump will wear out the pistons and piston seals prematurely.
There are two options to safely stop the pump flow when there is no solvent in the LC bottle. Both options can be used separately or simultaneously.
Bottle Fillings option
LC pumps have a bottle filling option where the user programs the Total Volume of the bottle, and the Actual Volume of solvent, and check the box to turn off the pump when it is out of solvent. (See Figure 1)
The Prevent analysis if level falls below option will still allow the pump to run but prevent further injections as the pump will go into a Not Ready state.
Caution: The user must remember to update the Actual Volume when refilling the bottles and ensure that the solvent filter is at the bottom of the bottle.
In pump method setup, it’s common to set the maximum pressure to protect the column and system. However, the minimum pressure limit is usually left at default 0.00. If this field is set to some value, say 10 to 20 bar, then it will trigger an error should the solvent run out.
Another useful way to use this field is to set a pressure lower than the operating pressure to trigger the pump to shut off. For example, for a system operating at 250 bar, the minimum pressure can be set to 200 bar to turn off the pump. A loss of 50 bar may indicate some has gone wrong, such as check valves sticking or a severe leak due to broken capillary. If the injections were to continue, the chromatography would most likely not be useable.
Figure 2. Pressure limits
Caution: If running a gradient, the pressure can vary widely depending on the solvent composition changes so make sure you know how low the pressure can get and set the minimum at a level lower than the lowest level during the gradient.
Learn how to effectively operate your Agilent LC system:
HPLC-INFII-1120r - Agilent OpenLAB CDS ChemStation - Acquisition (C.01.07) e-learning course available from Agilent education