What to do when backpressure increases?

An increase in back-pressure usually suggests either a guard or analytical column problem. To find exactly where the problem lies we suggest you remove the guard column (if you are using one) and replace the old cartridge with a new one.

If the original pressure is restored, you solved the problem.

If the pressure remains high, disconnect the analytical column from the system, backflush it (do NOT connect the column to the detector while doing so) and run a few column volumes of your mobile phase through the column.

If the problem still persists you may have some strongly retained contaminants in your column coming from your previous injections.
Run the appropriate restoration procedures, as suggested by the column manufacturer, and retest the column.

If the initial pressure is not restored you may have to change the inlet frit or replace the column.

Always run your system (2 to 5 ml/min) without the guard column and the analytical column to verify that your pressure isn’t coming from another source, like a blocked in-line column prefilter, blocked/kinked tubing, particulates blocking your injector etc.
Always work your way from the detector back to the pump to isolate the problem.