What causes high pressure in my HPLC 1100?

What causes high pressure in my LC?

Probable Causes: 1. Blockage in PTFE frit in the purge valve.
2. Upper pressure limit is set too low.
3. Blockage past the damping unit.
Suggested Actions: 1. Open the purge valve. If the pressure is still high, replace the PTFE frit in the purge valve.
2. Look at the upper pressure limit setting in the software and make sure it is set to a value suitable for the analysis.
3. Check for blockages. (See below)
To Check for blockages, use the split system approach for troubleshooting: Remove the column, pre-column and pre-column filter, if they are installed. 1. If the pressure returns to normal, install a ZDV fitting in place of the column.
a. If the pressure is normal, the column, pre-column or filter was the source of the problem. Replace it.
b. If the pressure is high, look for blockage beyond the column (example: tubing to or from the detector).
2. If the pressure is still high after removing the column, check the tubing from the purge valve to the autosampler. If pressure is normal, use the injector step commands to switch the injection valve of the autosampler to the bypass mode.
a. If the pressure is normal, there is blockage in the autosampler. Check the needle, needle seat, needle seat capillary tubing, and rotor seal.
b. If the pressure is still high, analyze the tubing from the injection valve to the column inlet.