This Information Applies To: Agilent analytical, micro, or preparative LC systems
Issue
The system is set up to run an analysis. The user installs the column and is flowing with the required mobile phase and method parameters. The expected backpressure should be 200 bar (for example) but it was higher than expected (e.g. 350 bar).
Steps to follow
The following flowchart (see Figure 1) guides the user through the steps (labeled 1 to 10) to systematically determine the source of the additional backpressure.
Figure 1. Flowchart for troubleshooting high backpressure in your LC system.
Every number corresponds to the following steps.
Step 1
Some pumps may not have a manual purge valve, so use the software to open the valve by starting a purge. If the pressure is not close to zero, the purge frit is clogged and needs to be replaced.
Step 2
Follow the procedure to replace the purge frit (How to Replace the PTFE Frit of the Purge Valve in LC Pumps).
Step 3
Close the purge valve and right click the Sampler icon and choose switch valve to bypass. The pressure may now be either 200 or 350 bar. If it’s 200 bar, the issue is between ports 2 and 5 on the injection valve with the most likely place for the clog being in the needle seat. Although it can be the needle as well.
If it’s 350 bar, the blockage is not in the Sampler.
Step 4
See these articles for instructions to back flush the needle seat and needle/sample loop (see Clear a Needle or Needle Seat Clog Without Using Lab Advisor as well as Backflushing the Needle Seat of the Agilent Vialsampler)
The capillary from the pump to the port 1 on the sampler can be the source of the clog as well, so remove from port 1 and put into a beaker. If the pressure is around 150 bar, then try back flushing the capillary and if not successful, replace it. If the pressure is just a few bars, then it’s okay so install it back into port 1 and continue troubleshooting.
Steps 7 and 8
The column inlet capillary is the capillary exiting from port 6 in the sampler injection valve. The capillary may be connected directly into a column (or HPLC guard column), to valves in the column compartment or to inline heaters. Whatever way the system is plumbed, follow the flow and remove the capillaries one at a time to determine the location of the clog. For example, if removing the capillary from the column inlet shows minimal pressure, then next remove the capillary from the column exit. If the pressure is 350 bar, then the clog must be in the column. If the pressure reads 200 bar after removing the column exit capillary, the pressure is downstream.
If the column is the source of the increased backpressure, then usually it may be possible to backflush the column. Check with the manufacturer’s recommendation first before performing a backflush on the column to prevent any accidental column damage.
If the clog is in the flow cell, then it too can be back flushed, but use caution when doing so (see Removing a Clog from a Flow Cell).
Steps 9 and 10
Upstream from the column may be an inlet filter, guard column, column heater, or a valve. Again, it will require systematically removing capillaries one at a time to determine the source of the clog. Most capillaries can be back flushed rather than replaced.
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Learn how to effectively troubleshoot your Agilent Infinity LC system:
HPLC-1260-1271e - HPLC High Pressure Errors HPLC-1260-1273e - Agilent 1260 Infinity LC with OpenLab CDS High Pressure Error eLearning courses available from Agilent education |
