High pressure in the Autosampler is usually in the seat capillary. Sample particulates or plugs from the vial caps can go up the needle when the Autosampler is drawing sample, then when the valves switches back to main pass, they are forced into the seat capillary.
To backflush the needle seat:
1) Turn on the pump flow rate to 3mL/min through ChemStation or through Lab Advisor.
2) Open the purge valve
3) Using Lab Advisor, go to the Maintenance section, highlight the Autosampler, and choose the maintenance position ‘replace needle’ for the Autosampler to lift the needle.
4) Disconnect the seat capillary from port 5 in the injection valve.
5) Keep the autosampler in the maintenance position.
6) Connect the needle seat capillary to port # 6.
7) Close the purge valve. Open the purge valve, then close the purge valve. Make sure to have kimwipes or paper towels to collect the mobile phase flow at the needle seat.
8) Once there is flow backwards through the seat capillary, open the purge valve.
9) Reinstall the needle seat capillary into port #5, return the capillary to the column or TCC to position #6, and then end the maintenance position.
10) Reset the Autosampler, disconnect the Instrument, and close Lab Advisor.
11) Open Chemstation and try normal flow rates. If pressure is fine now the procedure has worked.
If the clog was in the seat capillary, this has a good chance of unplugging it. If there is no flow out the needle seat and/or the pump pressures out, then the procedure was not successful and the seat capillary will need to be replaced.